By Peter Plumley

Presented at the 75th Annual Meeting of the Pacific Division of the American Association for the Advancement of Science, San Francisco State University, San Francisco, California, June 21, 1994.


Since the AIDS epidemic first appeared in the early 1980s, hundreds of thousands of people have been diagnosed with the disease. It has captured the attention of medical authorities, the press, the public, and many special interest groups. Billions of dollars have been spent on AIDS treatment, research, and attempts at prevention. In the process, AIDS has replaced smoking as the greatest single cause of statistics.

Unfortunately, AIDS is a complicated disease, poorly understood by the public. Furthermore, it affects different groups to vastly different degrees. Because of this, and because one of the means of transmission of HIV is by sexual intercourse, it has proven to be a fertile ground for special interest groups to pursue their various agendas. As a result, many of the statistics have been distorted, and many of the prevention efforts have been misguided and even counterproductive.

The professional training of the actuary includes the development of skills useful for analysis of data, modeling, and determination of risk levels. This paper examines the AIDS epidemic from the viewpoint of the actuary, with particular emphasis on the relationship of risk of HIV infection and AIDS to lifestyles and health.

It is well-known that most AIDS victims are either homosexual men or IV drug users, or both. For them, the risk levels are high. As will be shown in this paper, nearly all of these AIDS victims have a lifestyle that creates immune system disorders and is generally not conducive to good health.

At the same time, the vast majority of Americans are healthy heterosexuals. ("Healthy" within the context of this paper means free of street drugs, other sexually transmitted diseases, and immune system disorders which might make one susceptible to HIV and AIDS.) For them, the conclusions as to risk levels and best techniques for the prevention of HIV transmission can be summarized as follows:

1. Unless one has a regular sexual relationship with someone who is HIV-positive, it is virtually impossible to become infected with HIV by heterosexual intercourse.

2. Mutual monogamy provides little protection from AIDS, because most HIV transmissions from heterosexual contact are from someone infected by non-sexual means such as IV drug use or blood transfusions, to his or her regular (and quite possibly monogamous) sexual partner.

3. Multiple sexual partners involve little or no increase in risk of HIV infection, as compared with monogamous relationships.

4. Because the risk of HIV transmission is so extremely remote for this group. urging the use of condoms will do virtually nothing to prevent transmission of HIV. Therefore, because condoms intrude so much on the lovemaking process, there usually is little point in using one, unless it is felt necessary for the prevention of pregnancy or the transmission of other, more easily transmitted, sexually transmitted diseases ("STDs").

5. AIDS education and prevention efforts for heterosexuals, as presently structured, can be counterproductive, because it may create fear and paranoia which in turn may cause more of an increase in mortality than that from the rare case of HIV transmission that might be prevented. Instead, the focus of AIDS education and prevention for this group should concentrate on three points:

By far the most important way to prevent HIV infection is to maintain a healthy body, free of street drugs, other STDs, and immune system disorders, so that one's body will not be susceptible to HIV infection, if by chance one is exposed.

While the healthy person has little to fear from the "one-night" stand, a regular sexual relationship with an HIV positive person can involve significant risk because of the repeated exposure to HIV. Therefore, greater care should be used in choosing one's regular sexual partner.

Receptive anal sex presents a higher risk than vaginal sex, for several reasons. Therefore, if done at all, it should be done carefully and sparingly, and only with a reliable partner who is HIV-negative and free of any STDs.

Some of the actuarial analysis in this paper makes the implicit assumption that HIV causes AIDS. However, it should be noted that there is a growing body of scientific opinion that questions the role of HIV in AIDS. A full analysis of that issue is beyond the scope of this paper. What is clear, however, is that nearly all cases of AIDS are associated with other significant health problems which impair the immune system, and which are unrelated to HIV. In view of this fact, from the viewpoint of the actuary, mortality rates would be improved far more if the focus were more on the underlying causes (street drugs, anal sex, other STDs, etc.) of the immune system disorders affecting nearly all of those with AIDS, rather than merely trying to find a cure for HIV.

Distribution of AIDS cases in the United States

As of the end of 1992 (publication of the 1993 report having been delayed by the CDC), the cumulative distribution of adult cases since 1981 by exposure category was as follows:

Male homosexual/bisexual contact 142,626 (57%)

IV drug use (female and heterosexual male) 57,412 (23%)

Male homosexual/bisexual contact and IV drug use 15,899 ( 6%)

Hemophilia/coagulation disorder 2,026 ( 1%)

Heterosexual contact with a person with, or at increased risk for, HIV infection 13,292 (5%)

Born in Pattern II country 2,962 ( 1%)

Receipt of blood transfusion, blood components or tissue 4,980 ( 2%)

Other/undetermined 10,002 ( 4%)

Total 249,199 (100%)

The heterosexual contact cases are subdivided into the following categories, shown with cases reported through December 31, 1992:

Sex with IV drug user 8,481 (64%)

Sex with bisexual male 823 ( 6%)

Sex with person with hemophilia 131 ( 1%)

Sex with person born in Pattern II country 205 ( 2%)

Sex with transfusion recipient with HIV infection 311 (2%)

Sex with HIV-infected person, risk not specified 3,341 (25%)

Total 13,292 (100%)

As mentioned in the introduction, it is clear that, unlike many infectious or contagious diseases, AIDS strikes different groups very unevenly, and therefore the risk of contracting the disease varies significantly. This paper examines the epidemic from the point of view of the level of risk for each group, and the relationship of poor health and immune system disorders to these risk levels.

Reliability of the CDC's classification system

The CDC does not itself report AIDS cases; that is the responsibility of state and local health departments. The CDC states as follows in the information provided with its public data set with respect to the surveillance process:

"Although state and local health departments share AIDS surveillance data with CDC, the responsibility and authority for AIDS surveillance rests with the individual health departments. Like any reportable disease, the completeness of AIDS reporting reflects the aggressiveness with which these health departments solicit case reports. Health departments may depend on health-care providers to know and comply with reporting requirements. Alternatively, health departments may regularly contact and interact with health-care facilities or individual providers to stimulate disease reporting."

In examining the accuracy of the classification of cases by the CDC, it must be recognized that, except in perinatal cases, it is virtually impossible to know with absolute certainty how a particular individual became infected with HIV. Originally, AIDS was referred to as "GRIDS" ("gay related immunodeficiency syndrome"), because it appeared to be a disease which affected only homosexual men. Later, it became clear by statistical analysis that it primarily affected homosexual men and IV drug users, but that HIV could also be transmitted by penile-vaginal intercourse and blood transfusions, and from an infected mother to her child. All of these transmission methods are consistent with the fact that AIDS is a blood disease. However, even though the high risk categories are known, there is no way of knowing for certain whether a particular person became infected in a particular manner, because the precise details of one's life cannot be known with absolute certainty by others.

This is particularly important with respect to AIDS cases attributed to heterosexual contact, because so many homosexuals and IV drug users try to conceal their lifestyles. These are lifestyles which are condemned by a large part of our society, and which many times cause loss of jobs, ostracism, and criminal action. Studies have shown that AIDS cases which at first appeared to be attributable to heterosexual contact were actually linked to other risk classifications., The overall level of concealment which has occurred is difficult to determine, because it varies with the effectiveness of local health departments in determining the full facts. However, it may well be a significant part of the cases categorized as heterosexual contact, particularly for males. We sometimes read about how someone is supposed to have become infected with HIV under some unusual circumstance. This incident is then used to justify precautions against the spread of HIV, where none were felt needed previously. Yet in most cases, such precautions are not productive, because either (1) the cause of the HIV infection may have been misclassified, or (2) the risk is so remote that it is not worth the precautions that are being considered.

Risk of AIDS - risks of life

We are all "at risk" for AIDS - and for that matter, for death from many other causes, each day of our lives. Merely walking down the street could result in HIV infection from being stabbed with an HIV-infected needle. It also could result in death from falling objects, or from an out-of-control car, or a stray bullet. People have been killed in plane crashes while sleeping in their beds. "Freak" accidents occur nearly every day. And death from natural causes can strike, suddenly or slowly, at any age. Therefore it is pointless to try to lead a risk-free life. It just simply cannot be done, and those who try will be termed "paranoid" by their peers, and will do little to extend their life expectancy, while diminishing their enjoyment of life.

So the first challenge is to sort out the "significant" risks from the "insignificant" ones. But even here, it is not so easy. A 20 year old healthy man might well feel that unprotected sexual intercourse with an HIV-infected partner presented an unacceptably high risk. However, if he was 90 years old and the woman was young and beautiful, he might decide that the risk was well worth the reward.

Nevertheless, in order to discuss HIV and AIDS in terms of significant risk levels, we must have some type of benchmark. So let us start by considering how often we incur a "one-in-a-million" risk in our daily lives. The average risk of death from all causes for a 25-year old (both sexes and all races combined) is 1.18 per 1000 per year. This means that the average 25-year old has a "one-in-a-million" risk of death from all causes every 7 hours. Yet people at that age generally are not concerned about the risk of death in the near future, in the absence of a specific situation which is perceived to involve a higher risk.

Another instructive comparison can be made with automobile fatality rates. In 1988, there were 2.4 deaths from automobile accidents per 100 million vehicle miles. Assuming an average of 2 people per vehicle, this means that the risk of being killed in an automobile accident is "one-in-a-million" for every 83 miles traveled - less than two hours time at normal highway speeds. (Considering the higher automobile fatality rates for younger drivers, the number of miles presumably is significantly lower for the 25-year old.)

A 1991 television special also referred to "one-in-a-million" risks. It stated that one increased his risk of dying by one-in-a-million by:

Traveling six miles in a canoe

Traveling 10 miles

on a bicycle

Spending one hour in a coal mine

Smoking 1.4 cigarettes

This author has made no attempt to verify the accuracy of these figures; however, they are further demonstration that most of us take "one-in-a-million" risks routinely in our lives, without undue fear of the consequences, simply because we believe that the risk is too insignificant to worry about. In examining the AIDS epidemic in terms of how it should affect our daily behavior, it is important that we realize that our lives are full of "one-in-a-million" risks, many of which we cannot avoid no matter how hard we try. We of course should be aware of the dangers of "high-risk" activities of any type so that we can avoid them if we do not want to take the risk. At the same time, we should recognize that some activities which are described as putting people "at risk" for HIV infection in fact involve "one-in-a-million" risks such as those described above, and therefore might reasonably be ignored in going about our everyday lives.

The difficulty of transmission of HIV by heterosexual contact

Most STDs have a fairly high efficiency of transmission - perhaps a 10% to as high as a 50% probability of transmission during a single sexual act with an infected partner. As a result, the typical route for such diseases is from male-to-female-to-male-to-female..., by heterosexual intercourse. Obviously, therefore, the best defenses against the spread of such diseases are (1) monogamy, (2) condoms, and (3) medical treatment when symptoms occur.

HIV, however, is very different in one fundamental respect. Although it has been demonstrated that the transmission of HIV by heterosexual intercourse is possible, both male-to-female and female-to-male, unlike most other sexually transmitted diseases, the transmission is extremely inefficient, particularly female-to-male.

In addition, transmission usually is associated with some type of abnormality, such as some other STD. This was dramatically illustrated in a paper titled "Female-to-Male Transmission of Human Immunodeficiency Virus", by Padian et al, published in the September 25, 1991 issue of the Journal of the American Medical Association. In this paper, 72 male, non-drug using partners of HIV-positive women were studied, beginning in 1985. Of the 72 males, only a single one became infected through sexual contact. It is instructive to quote excerpts from the description of this couple's sexual practices and physical condition, to show the conditions which caused the man to become infected.

"Over the five years prior to the study, [the woman] had over 600 male partners, including over 2000 contacts with a bisexual man, an unidentified number of contacts with an intravenous drug user, and over 1000 contacts with a person she knew to be HIV-infected.

"The couple reported an average of 15 sexual contacts a month for the last 7 years. Almost all of these contacts consisted of unprotected vaginal-penile and oral intercourse. The couple practiced anal intercourse twice. The couple never used condoms. ... The woman would frequently have sexual intercourse with another partner while her husband first observed and then had intercourse with her immediately after the other partner.

"This couple reported ... over 100 episodes of both vaginal and penile bleeding. The cause of this bleeding could not be established. Medical data were available only by history, and over the last 5 years, the woman reported four cases of vaginal yeast infections, both reported one case of trichomoniasis, and the man reported one case of urethral gonorrhea. In addition, the woman reported a history of endometriosis and had a hysterectomy during the year prior to entry into the study."

The report goes on to suggest that the man's HIV infection may have come from one of the other men who had sexual relations with his wife immediately prior to his sexual activity, rather than from his wife.

The report also states that six other of the 72 men reported penile bleeding during sexual intercourse, but did not become infected.

It is not at all surprising that this one man became infected, given his history of penile bleeding and other STD's. In fact, it illustrates that the risk of transmission of HIV infection may depend on a variety of factors relating both to the degree of infectiousness of the infected partner and to the susceptibility to infection of the uninfected partner. Of particular interest in this regard is the paper "Biologic Factors in the Sexual Transmission of Human Immunodeficiency Virus", by Holmberg et al. This paper discusses a number of possible cofactors, and concludes with the following summary:

"The probability that any single episode of genital-genital or anogenital sexual intercourse will result in transmission of HIV may be determined by multiple biologic factors of the infectious person, the virus itself, and the exposed susceptible person. Some of these factors are known or suspected (figure 1), and they may explain observed differences in the sexual transmission of HIV in different parts of the world, notably in Africa, where genital ulcerative disease is probably influencing the epidemiology of HIV. Several studies have shown that infection in partners of HIV-infected persons is not determined solely by numbers of sexual encounters; on the contrary, HIV-infected partners have usually had fewer sexual encounters with infectious mates than have noninfected partners.,, Thus, sexually active persons should be cautioned that, to our knowledge, there are no nonsusceptible persons and that any single sexual encounter may lead to HIV transmission. Research into biologic factors that modulate HIV transmission continues to be hampered by difficulties in identifying HIV transmitters and nontransmitters, infective and noninfective variants of HIV (if the latter exist in vivo), and persons relatively more or less susceptible to HIV infection. However, as the number of partner studies and the number enrolled in them increase, a progressively clearer idea of the biologic determinants of sexual transmission should emerge."

The "figure 1" referred to above shows the following biologic factors considered possible risk factors in the sexual transmission of HIV. Question marks indicate factors whose effect in enhancing transmission are debatable, in the opinion of the authors of the paper.

Host Infectiousness:

Late HIV infection: marked by low T-helper cell levels. p24 antigenemia, clinical symptoms (?) Early HIV infection: marked by increased T-suppressor cells, and (?) p24 antigenemia and (?) elevated antibody titers to cytomegalovirus (CMV)

(?) Menstruation (female-to-male transmission)

(?) Lack of integrity of vaginal sucosa from genital ulcer disease (female-to-male transmission)

Viral Virulence/Infectivity:

(?) Variation in the viral genome, resulting in increased or decreased infectivity

Host Susceptibility:

Genital ulcerative disease from herpes simplex virus type 2 and syphilis (Western industrialized societies) and by chancroid and syphilis (Africa)

(?) lack of circumcision in men: intact foreskin

(?) Trauma during sex, especially in post-menopausal women

(?) Estrogen (birth control pill) use in African prostitutes

(?) Variants of CD4 receptor molecule of T-lymphocytes

(?) HLA haplotype or other cell surface antigens

Is it theoretically possible for a fully healthy heterosexual to become infected with HIV from a single act of heterosexual intercourse with an HIV-positive partner? Holmberg et al believe that it is. On the other hand, as stated earlier, it is never possible to be absolutely certain how a person became HIV-positive, simply because we can never know of all of the details of anyone's life. Thus the supposedly otherwise totally "clean living" victim of the "one night stand" may have had a secret drug habit, or other venereal disease, which placed him or her at risk. It is only when a significant number of such instances occur that we can be reasonably certain that that means of transmission really does occur, rather than simply indicating some kind of aberration or misclassification.

In any event, it is clear that the average efficiency of HIV transmission among people of average health is extremely low. Moreover, for the "one night stand", it appears to be virtually zero in the absence of some cofactor such as other STD or penile bleeding. Robert Root-Bernstein sums it up in his book "Rethinking AIDS" as follows:

"In short, although HIV certainly can be transmitted through semen from one person to another, it is in fact transmitted so rarely to healthy sexual partners and is present at such low amounts in so few sperm samples from HIV-infected men that it is probable that those who become infected must be exposed repeatedly to many HIV carriers or have some unusual susceptibility to the virus."

Root-Bernstein further states (p. 313), that "The chances that a healthy, drug-free heterosexual will contract AIDS from another heterosexual are so small they are hardly worth worrying about. One statistician has compared them to the probability of winning a state lottery game or being struck by lightning." Root-Bernstein goes on to quote a report in the journal Science which states that the chance of becoming infected with HIV after one sexual fencounter, without using a condom, with someone whose HIV status is unknown, but who does not belong to any high-risk group, yields a calculated risk of 1 in 5 million.

Some important implications of the low efficiency of HIV transmission by heterosexual contact

The low efficiency of transmission of HIV by sexual intercourse results in some fundamental differences between HIV and other STDs. These include the following:

It can be mathematically demonstrated (see Appendix A) that the lower the efficiency of transmission of a sexually transmitted disease, the greater the proportion of transmissions will occur between regular partners, rather than secondary partners (e.g., "one night stands"). Most heterosexuals who get HIV do so by sharing IV drug needles, not from sex. Some of them in turn infect their sexual partners - generally their regular partner. Therefore, mutual monogamy does little to reduce the transmission of HIV - even if both partners have tested negative for HIV at the time the monogamous relationship began.

The number of heterosexual partners makes little difference in the risk of HIV infection (although the type of partner may make a difference). This also can be demonstrated mathematically (see Appendix B). It even is theoretically possible, in fact, that for a given amount of sexual activity, multiple partners might reduce risk because of greater sexual arousal, and therefore better vaginal lubrication and consequent lower efficiency of HIV transmission. (Obviously, those who became infected from their regular partner might have been better off if less of their sexual activity had been with that person!)

Only very rarely does someone become infected with HIV from engaging in penile-vaginal sex with someone who in turn became infected in the same manner (rather than from IV drugs, homosexual activity, or some other means such as a blood transfusion). Therefore it usually makes little or no difference whom your sexual partner has had heterosexual relations with previously (though it would matter if a man's previous partners were male).

HIV risks for those with multiple sexual partners

In Appendix B, it is demonstrated that, for a disease with as low an efficiency of transmission as HIV, the number of sexual partners makes little difference. This theoretical result appears to be validated by an examination of the experience of those who are known to have many partners. Let us look at three groups: (1) professional athletes, (2) "swingers", and (3) prostitutes.

HIV and professional athletes

Several years ago, Magic Johnson was forced to retire from basketball when he was discovered to be HIV-positive. He claimed to have become infected from unprotected sexual activity, and admitted to having had a large number of sexual partners, without using condoms. Much was made of this by the media and health care officials, and his experience was used to demonstrate the "high risk" involved with unprotected sex with multiple partners.

However, a further analysis suggests that the risk wasn't so high after all. Since the AIDS epidemic began, there have been hundreds, if not thousands, of professional sports figures who would have made the headlines if they had been found to be HIV-positive. Sports figures are noted for their sexual activity - a reputation deserved by some, and not by others. Yet to the best of this author's knowledge, Magic Johnson is the only one to have fmade any such headlines (except for Arthur Ashe, who was known to have become infected from a blood transfusion). To this day, it is not certain exactly why Magic Johnson became infected while others have not. Therefore, although it is not possible to develop a reliable risk factor for professional athletes, his experience appears to be more of an faberration or misclassification than something which is likely to befall other athletes.

HIV and social/sexual clubs

Another group with multiple sexual partners are the members of social/sexual clubs, commonly known as "swingers". Swingers engage in recreational sexual activity with multiple partners. In many cases, these sexual partners were strangers when the evening began. There are more than 200 swingers clubs in the U.S. and Canada, with a membership totalling perhaps 100,000, according to one magazine report. Swingers generally do not use condoms. Therefore they provide in effect a made-to-order laboratory for the study of transmission of HIV through multiple sexual partnerships and unprotected sex. If in fact the swinging lifestyle did present an "increased risk" of HIV infection, by now there would have been many cases of HIV and AIDS among the various swing clubs (or, more likely, the clubs would have closed up because of the unacceptability of the high risk).

However, there has been only one reported episode of HIV infection among members of a swingers club. It involved anal rather than vaginal sex, and was reported by the CDC. In this instance, which occurred in 1986, all of the members of a swingers club were tested, and two female members were found to be HIV-positive. Both had engaged in repeated anal intercourse with two bisexual men whose HIV status could not be determined. As will be seen later in this paper, receptive anal intercourse appears to involve much higher risk levels than penile-vaginal sex. Presumably they became infected from the anal sex, rather than from vaginal sexual activity. They did not infect any of their male sexual partners, even though their HIV status was not detected until some time after their infection occurred, during which time they continued their sexual activity with various other partners.

A recent article in Penthouse magazine titled "Swinging Swings Back" described the resurgence of swinging. As might be expected, the article included some "hand wringing" about the risks of AIDS being taken by these people, including a quote from a representative of the CDC that swingers were "just whistling past the graveyard".

Yet the facts are to the contrary. Robert McGinley, President of the North American Swing Club Association, is quoted in the Penthouse article as stating categorically that "as far as we can tell, no person has ever contracted AIDS through heterosexual [i.e., penile-vaginal] swinging in North America". His statement appears to be correct. This author has been unable to find any data which contradicts his statement or suggests anything to the contrary.

How can this be, in the face of all of the warnings about the high risk of unprotected sex, particularly with multiple partners who frequently are relative strangers?

The answer appears to lie in the ethics of the swinging lifestyle, and in the type of people who are involved in swinging.

For obvious reasons, swingers clubs will not allow any members under age 18, and usually not under age 21. In addition, swingers generally are "middle class" types who have a primary sexual partner, with whom they are involved in a regular, frequently long-term relationship. Therefore, they tend to be a generally healthier group than those most susceptible to HIV and AIDS.

Because swingers are potentially vulnerable to the spread of the more contagious STDs, they are careful to watch for the symptoms of any STDs, and to take appropriate steps to correct any problems as quickly as possible, on those rare occasions when they occur.

Swingers realize that, while authorities cannot legally prevent adults from engaging in consensual heterosexual activities, many disapprove of their lifestyle and would shut them down if they had an excuse to do so. Therefore, swingers clubs are very strict about forbidding illegal drugs, and generally will throw out anyone who disobeys this prohibition. By doing this, the clubs keep out the primary source of heterosexual HIV infections.

What is the lesson to be learned from the swingers about the risk of HIV infection from heterosexual (vaginal) intercourse? It is this: keep your body in good health, and free of other STDs, avoid any regular sexual relationships with high risk people such as drug users, and you don't need to worry about AIDS.

HIV and female prostitutes

Prostitutes are another group which engages in sexual activity with multiple partners. Root-Bernstein discusses their experience as follows:

"M. Seidlin and his colleagues examined the prevalence of HIV infections in New York City call girls during 1987, They studied seventy-eight women who had been prostitutes for an average of five years each. Each woman had had an average of over 200 clients during the past year, or approximately 1,000 lifetime partners. Use of condoms was sporadic at best. Vaginal intercourse was common; anal, rare. Since it is estimated that nearly 5% of men in New York City are thought to be intravenous drug users and half of these are HIV seropositive, it is probable that each of these prostitutes had sexual relations with an average of twenty-five HIV-seropositive individuals. Despite this unusual promiscuity and despite living in one of the AIDS capitals of the world, only one of the women was HIV seropositive. She admitted being an intravenous drug abuser. Her seventy-two non-drug abusing co-workers were all HIV negative.

"Another study carried out in New York City by Dr. Joyce Wallace and her co-workers between 1982 and 1988 found similar results. They surveyed several hundred streetwalkers (a lower class of prostitute than call girls) for a variety of measures of immunodeficiency. Excluding admitted intravenous drug users from their study, they found that only 4.5 percent of the prostitutes were HIV infected. The only statistical difference between those who were infected and those who were not was that the HIV-positive women had had a mean of 3,062 sexual partners during their lifetime, whereas the HIV-seronegatives had had 1,047. On the other hand, Wallace found an HIV seropositivity rate approaching 50% among drug-abusing prostitutes."

Similarly, a 1988 study concluded that "HIV infection in non-drug using prostitutes tends to be low or absent, implying that sexual activity alone does not place them at high risk, while prostitutes who use intravenous drugs are far more likely to be infected with HIV".

Given the level of STDs among streetwalker prostitutes, and the desire by some to try to conceal their drug habit, it is not surprising that a small percentage of those who did not admit to drug use nevertheless were HIV-positive. All things considered, it is significant that the percentage was so low, and is another indication of the extreme difficulty of HIV transmission by heterosexual intercourse.

Condoms - common sense or nonsense?

The low average efficiency of transmission of HIV raises serious doubts as to the value of the emphasis being placed on the use of condoms for the prevention of transmission of HIV infection during heterosexual intercourse, for several reasons:

The vast majority of people are (1) in good health and free of STDs, and (2) not sexually involved on a regular basis with anyone who is in a "high risk" group (i.e., an IV drug user or a homosexual/bisexual). For them, the risk of HIV infection from sexual intercourse is so remote (generally considerably less than one chance in a million per episode) that using a condom is comparable to wearing a hard hat for a walk down Main Street - it may be theoretically possible that it could save your life, but it really isn't worth the bother and inconvenience, considering the remoteness of the risk.

Condoms are more likely to be used for casual sex, and by those who are "safety-conscious" and unlikely to be involved with IV drug users or other "high-risk" sexual partners. However, the majority of transmissions of HIV from sexual intercourse occur between regular partners, where one partner became infected from some non-sexual means such as IV drug use or blood transfusion.

Condoms may create a false sense of security (they are not foolproof, and have shown a failure rate of from 10% to 20%), and may cause an increase in sexual activity or a less careful choice of sexual partners.

Finally, who is supposed to use condoms, anyhow? If they are to be used only for casual sex, very few cases of HIV transmission will be prevented. If they are to be used for all sexual activity, are we proposing reducing the birth rate to zero to prevent HIV transmission? (It is to be noted in this respect that in Africa, where life expectancy is low and the need to reproduce is more keenly felt than in the United States, some are concerned that the emphasis on condoms will have an adverse effect on the population demographics because of the impact on birth rates.)

Condoms make good sense in some situations, particularly for young people for whom the risk of unwanted pregnancy and STDs is high. Condoms are one method of birth control (though usually not the best one). They also can reduce the spread of the more easily transmitted STDs. However, the blunt truth is that, in spite of all of the public health campaigns urging their use, they will have virtually no effect on the spread of HIV and AIDS among heterosexuals.

AIDS and homosexual men

In contrast to the low risk for heterosexuals, homosexual men incur a significant risk because of their lifestyle. Root-Bernstein details the many immunosuppressive risk factors that affect homosexual men. Many of these, such as syphilis and a variety of other infections, are associated with anal sexual practices engaged in by a significant percentage of homosexual men. However, other risk factors were related to the widespread use of various drugs by homosexuals. In this respect, Root-Bernstein quotes the following studies:

"A CDC survey conducted in 1983 found that a 'typical' gay man in New York, Los Angeles, and San Francisco used four street drugs regularly. Those who had developed AIDS by 1983 had a history of increased drug use both in therm of frequency of use and number of different drugs used regularly. Ninety-five percent of the gay men surveyed regularly used inhalant nitrites; over 90 percent smoked marijuana; 60 percent used cocaine; about 8 percent used heroin; over 50 percent used amphetamines; over 30 percent, barbiturates; almost 50 percent, LSD and methaqualone; and about 40 percent had used phencyclidine. Linda Pifer's 1987 survey of gay men in Memphis found slightly lower rates of drug use. Over 80 percent of this group admitted to using nitrites at least occasionally and 30 percent more than once a week. Seventy-four percent admitted to use of other illicit drugs, including marijuana, cocaine, phencyclidine, and LSD, with an average of nearly seven years of 'routine use.' Eleven percent described themselves as being 'heavy drinkers' and another 37 percent as 'moderate drinkers.' Multiple drug use was the norm among the heavy abusers."

The increased risk of HIV infection for those homosexuals (and heterosexuals) who engage in anal sex is described by Root-Bernstein as follows:

"Immunological contact with sperm, or material carried in sperm, is increased in anal, as contrasted with vaginal or oral, intercourse. On reason has to do with the physiological differences of the rectum, vagina, and upper gastrointestinal tract. Vaginal tissue differs markedly from rectal tissue. The vagina has thick, muscular walls covered by a fdeep layer of epithelial (skin-like) cells that are easily sloughed off and secrete a lubricating mucus to decrease the possibility of abrasion. Even if abrasion does occur, the capillaries that embedded in the vaginal tissue are far from the surface and difficult to reach. There are also very few lymphocytes directly in the vagina, most of them being located higher up, near the cervix. The rectal tissue presents an entirely different picture. The rectum is comprised of an extremely thin layer of tissue, densely entwined with capillaries. It lacks the thick layers of epithelium that protect the vagina and its ability to produce a protective mucus. Moreover, the intestines are studded with Peyer's patches. Located along with the Peyer's patches are concentrations of M cells, which apparently function as portals through which the resident lymphocytes constantly sample the contents of the rectum for foreign material. These M cells have been shown to permit viruses such as HIV to gain access to the immune system from the rectum. Thus, unlike the vagina, the rectum represents a place in the body through which the immune system can easily be reached, even under normal conditions. Since microscopic tears and bleeding can accompany anal intercourse and infections but are rare in vaginal intercourse, anal exposure confers another means for semen components (and viruses) to enter the bloodstream, there to be immunologically processed."

Root-Bernstein then goes on to list a number of diseases that may develop in the rectum as a result of the various anal sexual practices engaged in by homosexual men. It is no wonder that, even apart from AIDS, homosexual men who engage in anal sexual activity have a higher incidence of immunosuppressive disease than heterosexuals.

AIDS and drug use

It is well known that IV drug users are at high risk of AIDS. The reason for this is believed to be the sharing of needles. To reduce this risk, there are "clean needle" programs in some areas, through which IV drug users are provided with clean needles so that there will not be HIV transmission during the injection of IV drugs.

There is no doubt that IV drug users are at high risk for a variety of conditions relating to damage to the immune system, and there is little to be gained by elaborating on this point here. However, what is not usually emphasized is that those who use non-intravenous drugs also are damaging their immune system, and in the process leave themselves open to various immunosuppressive agents. Root-Bernstein sums it up as follows:

"The various immunosuppressive effects [of drug use] occur independent of the route by which the drugs are administered. It does not matter to the immune system whether the drugs are smoked, injected intravenously, injected by 'skin popping' (the technique used in tuberculin testing), or taken by oral or nasal routes. As long as the drug appears in sufficient concentrations in the blood for a long enough period of time, it will lead to both short term and long term immune suppression, with specific effects on T cells. A common result, particularly of heroin addiction and high dose cocaine use is an inversion of the T helper/ T-suppressor ratio, such as that seen in AIDS. Thus, one important feature of drug abuse that has not been taken into account in defining who is at risk for AIDS is the possibility that nonintravenous drug abusers who are exposed to HIV or other immunosuppressive agents by sexual routes will be at as great a risk of AIDS as are intravenous drug abusers. This fact may help to explain why so many sexual partners of intravenous drug abusers - people who are almost all drug users themselves - are developing AIDS despite the fact that they do not share needles."

The misinforming of the public

For better or for worse, we live in an age of the "thirty-second sound bite". Most of the public gets its knowledge about matters such as AIDS from the evening news, newspaper headlines, and other easy to absorb sources such as talk shows and advice columnists. Relatively few people acquire much knowledge from more reasoned sources such as scientific studies or in-depth analyses such as might be presented in serious books or articles in scientific publications.

The AIDS epidemic has provided the popular media with ample material. There have been many warnings given to the public about the dangers of contracting HIV by sexual intercourse. In addition, there have been stories of people who have supposedly contracted HIV from what normally would be considered to be casual contact. A number of groups have had a self interest in making the epidemic appear worse than it really is. Only rarely is the low risk level for heterosexuals mentioned. The result is that the public has been badly misinformed, and in the process has been terrorized far more than justified by the facts.

The misleading of the public has appeared in many forms, but in general has fallen into several broad categories:

Gross exaggerations of the extent to which the epidemic would spread among heterosexuals. Example: The statement heard by millions of television viewers in February, 1987, that "Research studies now project that one in five - listen to me, hard to believe - one in five heterosexuals could be dead from AIDS at the end of the next three years. That's by 1990."

Failure to recognize the low efficiency of transmission of HIV by making the implicit assumption that sexual activity with an infected partner will cause the virus to transmit 100% or nearly 100% of the time. Example: The letter published by a nationally syndicated columnist from a woman who said "Last night I had sex with 4,096 people... I had sex with a man (who) admitted to having sex with eight...female partners during the past year... I took those eight women and assumed that they also had slept with eight men, and each of those eight men had had sex with eight women, etc. By using simple arithmetic progression, after only three series I realized that I had been exposed somewhere along the line to 4,096 persons, plus one. How can I assume that there was no one in that family tree who was not an AIDS carrier...?" The columnist had no quarrel with the analysis, and replied, "You have focused on the aspect of AIDS that makes it such a terrifying disease."

Overemphasis by the media on isolated cases because of their human interest and dramatic appeal, even though they represent situations in which the risk is so remote, and many times so unproven, as to be unworthy of serious concern. Those familiar with the news business know that the unusual will make the evening news, particularly if sex is involved. Thus the thousands of homosexual men and IV drug users who are HIV-positive no longer are newsworthy; however, the person who claims, rightly or wrongly, to have contracted HIV from some act not generally thought to be capable of transmission of HIV will be given prime air time. Example: Kimberly Bergalis, who claimed, perhaps incorrectly, to have contracted AIDS during the course of dental treatment.

In the case of most news stories of unusual incidents (e.g., an airplane killing people asleep in their beds), the public generally will understand that it is not something likely to happen very often, if ever again, and will not be concerned. However, the public has so little understanding of the risk levels for AIDS that each report of a freak occurrence is interpreted by many as a new method of transmission, and a new and significant risk to be avoided at all costs.

Allegations that HIV can be transmitted in ways not possible. Example: A recent letter to an advice columnist from a mother who complained that she would have to have her child tested repeatedly for HIV because she had picked up a used condom in a hotel room and put it to her mouth. The columnist published the letter, and made no effort to tell the mother that her child could not possibly get AIDS in that manner.

Misuse of statistics. Example: The 1991 headline stating "Illinois AIDS Cases Doubled Since '89". The impression given is that the rate of AIDS cases had doubled. In fact, the story merely stated that the number of cases reported during the most recent two years was approximately the same as the total number reported previous to the most recent two years, so that the cumulative number of cases was double what it had been two years earlier. (By the headline's logic, deaths from any cause could be said to be on the increase!)

Mistakes of fact, even in publications which generally are relied on as being accurate. Example: The table heading in the 1991 Edition of The World Almanac and Book of Facts listing "U.S. Metropolitan Areas with AIDS rates of 25% or More, 1989-1990, and Cumulative Totals". Examination of the table reveals that it lists cities in which the AIDS rates were more than 25 per 100,000, not 25 per 100.

Because AIDS is almost uniformly fatal, and because one of the ways that HIV can be transmitted is by sexual intercourse, the epidemic has gotten the attention of the public in a big way. Unfortunately, there are many misunderstandings about AIDS and the risk of contracting HIV, as evidenced by a survey conducted in August, 1987 by the National Center for Health Statistics. Respondents were asked the question "How likely do you think it is that a person will get the AIDS virus from the following". Answer choices offered were "very likely", "somewhat likely", "somewhat unlikely", "very unlikely", "definitely not possible", and "don't know". The replies clearly showed the extent to which the public misunderstood the risk of contracting HIV.

69% believed that it was "very likely" or "somewhat likely" that one would get the AIDS virus from receiving a blood transfusion. (Even though there have been a number of unfortunate cases of HIV infection from blood transfusions before screening procedures were improved, the correct answer always was "very unlikely".)

25% believed it "very likely" or "somewhat likely" from donating blood. Only 18% correctly believed it to be definitely not possible.

21% believed it "very likely" or "somewhat likely" from working near someone with AIDS. Only 18% correctly believed it to be definitely not possible.

35% believed it "very likely" or "somewhat likely" from eating in a restaurant where the cook has AIDS. Only 11% correctly believed it to be definitely not possible.

47% believed it "very likely" or "somewhat likely" from sharing plates, forks, or glasses with someone who has AIDS. Only 8% correctly believed it to be definitely not possible.

31% believed it "very likely" or "somewhat likely" from using public toilets. Only 13% correctly believed it to be definitely not possible.

41% believed it to be "very likely" or "somewhat likely" from being coughed on or sneezed on by someone who has AIDS. Only 9% correctly believed it to be definitely not possible.

38% believed it to be "very likely" or "somewhat likely" that a person could get AIDS from mosquitoes or other insects.

Finally, 92% said that it was "very likely", and another 5% said that it was "somewhat likely", that a person would get the AIDS virus from having sex with someone who has AIDS. Less than 3% understood that the low efficiency of transmission made it unlikely.

Subsequent surveys have shown some improvement in the public's knowledge about the risk of transmission of HIV. Nevertheless, most people are still unaware of how difficult it is to transmit HIV by penile-vaginal sexual activity, and significant proportions of the population still believe that HIV can be transmitted by various types of casual contact, even though there are no known cases of the types of transmission referred to in the survey.

The risks of the fear of AIDS

In recent years, a great effort has been made to educate the population on the danger of contracting HIV, and what to do to reduce or avoid the risks. These efforts have been warranted with respect to male homosexuals and IV drug users, for whom the risks have been high. They also are warranted for those heterosexuals whose regular sexual partners are likely to be drawn from within the IV drug community.

However, the fear of AIDS has done great harm to the personal rights of those known or even suspected of having the disease, or being part of a high-risk group. The cases of unfair and unnecessary discrimination against such persons which have taken place because of these exaggerated fears number in the thousands. In 1990, the American Civil Liberties Union ("ACLU") published a report titled "Epidemic of Fear". To produce the report, the ACLU sent questionnaires to more than 600 legal and advocacy organizations in the United States. The 260 that responded reported receiving or referring approximately 13,000 complaints of HIV-related discrimination from 1983 to 1988. Since then, many thousands more have surfaced. Indeed, the problem of AIDS discrimination was recently highlighted by the Academy Award winning movie "Philadelphia", which dealt with employment discrimination against an HIV-positive person.

Considering that the risk of heterosexually transmitted HIV is so small, is it also possible that, apart from the discrimination problems, the fear of AIDS can do more harm than the disease itself to the average middle class heterosexual not involved with IV drug users?

There is of course no one correct answer to this question. For some, the perceived dangers of AIDS merely provides an excuse to avoid relationships which they would prefer not to have anyhow. But for others, they may cause a number of undesirable results:

Fear and paranoia about AIDS may impair the healthy sexual activity necessary for the enjoyment of one's adult life.

Unnecessary or exaggerated alarm sounded by public health officials could adversely affect their credibility. This would make it more difficult to convince people that there was a real danger to public health in some future situation.

People may avoid medical treatment that they need, because of a fear of becoming infected with HIV while under treatment. One must wonder how many already have not agreed to necessary surgery, or skipped a visit to the dentist, because of headlines about persons getting HIV infections from surgeons and dentists. The risk of avoiding or delaying necessary medical attention almost surely is greater than the risk of HIV infection.

There may be added stress, with resulting health and other problems - for example, sexual dysfunction caused by fears about AIDS among those who actually had no reason ever to be concerned. Many prisons permit conjugal visits, in order to relieve stress and reduce the risk of riots and other violence. Is it possible that "AIDS education" is in fact a contributing factor in the violence we are experiencing today throughout the country?

Finally, people may delay or avoid the development of relationships which lead to marriage and the raising of families.

There does not appear to be any precise way to measure the effect of AIDS-related stress on mortality and morbidity levels. However, the following comparison is instructive. If a 25-year old man has one evening of sexual activity each week for the rest of his life with someone not in a high-risk group, the risk of AIDS will reduce his life expectancy by less than a single day, assuming that risk levels remain as they are today, and that HIV infection means certain death. On the other hand, a 1% increase in mortality from heart disease caused by added stress levels would reduce his life expectancy by 18 days.

Does HIV cause AIDS?

After more than a decade of hearing that "HIV is the cause of AIDS", there now is a growing body of opinion that this is not necessarily true after all. Today, we can hear knowledgeable people take a position all the way from "HIV is the sole cause of AIDS, and if you are HIV-positive you will eventually get, and die from, AIDS (if, of course something else doesn't kill you first)", to "HIV is unrelated to AIDS".

Clearly, there is a correlation between HIV and AIDS.

This is not surprising, since the definitions of "AIDS" have been closely associated with the finding of antibodies to HIV in blood tests. However, this does not necessarily mean that HIV causes AIDS, any more than the correlation between the increase in the cost of baseball tickets and football tickets means that one caused the other. In fact, of course, both are caused by other, external factors, some of which may be common to both increases.

Similarly, nearly all of those with the disease defined as "AIDS" (which has been changed several times) have one or more immune system problems, as do those who have been diagnosed as "HIV-positive."

1. Male homosexuals with AIDS nearly always have a history of drug use (which is damaging to the immune system, regardless of the nature of the drugs), and frequently have one or more sexually transmitted diseases associated with anal sex.

2. IV drug users obviously seriously abuse their bodies and always have immune system disorders.

3. Hemophiliacs also always have obvious immune system disorders.

4. People who receive blood transfusions also have had some type of illness or injury, in many cases involving immune system disorders of some type.

5. Heterosexuals who are categorized as having gotten AIDS from heterosexual contact are usually involved sexually with drug users, and likely have done drugs themselves (though not necessarily IV drugs). Only rarely does someone become HIV-positive from penile-vaginal sexual contact unless he or she has some type of health problem which sharply increases susceptibility to HIV and AIDS.

Thus, while one theory is that HIV "causes" AIDS, is it not also possible instead that the underlying immune problems affecting those who constitute virtually all of those who are diagnosed with AIDS also are causing these people to develop AIDS, or at least to be far more susceptible to it if they have HIV? As a minimum, there appears to be much to be learned about the relationship between HIV, other immune system disorders, and AIDS.

Does any otherwise fully healthy person get AIDS solely because of being HIV-positive? Some appear to do so. However, nearly all cases of AIDS can be proven to be associated with other significant health problems affecting the immune system. Many of the cases that cannot be proven to be so associated probably in fact were, if the full facts were known. So while HIV infection may be a factor in the development of clinical AIDS, health problems and immune system disorders appear to be at least as closely associated with the disease as is HIV. In view of this fact, from the view point of the actuary mortality rates would be improved far more if the focus were more on the underlying causes (street drugs, anal sex, other STDs, etc.) of the immune system disorders affecting nearly all of those with AIDS, rather than merely trying to find a cure for HIV.

In other words, without HIV, people still would be dying from the many immune system disorders associated with drugs and sexually transmitted diseases. However, if people did not destroy their bodies in those ways, there probably would be few cases of HIV, and little in the way of an AIDS epidemic.


The latest available data shows that deaths from AIDS are running at about 45,000 per year. This is about 2% of the total deaths in the United States. Most experts agree that the number of AIDS cases is leveling off, so that it is unlikely that the number of deaths from AIDS will ever be much in excess of 50,000 per year.

Viewed from this perspective, the money being spent on AIDS research is far in excess of that which can be justified on the basis of the number of deaths, as compared with such diseases as cancer and heart disease, each of which is responsible for far more deaths. At the same time, the AIDS epidemic represents an opportunity for important research regarding the body's immune system - research which can eventually benefit all of us, including the millions who will never have any contact with AIDS as a disease.

However, while it may be argued that research into the cause and cure for AIDS is worthwhile, current efforts at AIDS education and prevention are badly misdirected. As we have seen, the public is terrorized about AIDS, and in many cases sees risk where little or none exists.

The tragedy about our current efforts of AIDS education and prevention is that we are missing a unique opportunity to use the AIDS epidemic to scare people into better health by emphasizing that healthy people rarely ever get AIDS. Instead, we are using AIDS to sell condoms and to try to change the sexual desires of the public. In the process we have created a climate of fear and paranoia which has done great harm, while contributing little to controlling the AIDS epidemic.

As we have seen, nearly all AIDS victims have one or more health problems, generally involving the immune system, which has left them unusually susceptible to HIV and AIDS. With health care costs increasing rapidly, and with strong public pressure for health care cost containment and universal health care, the opportunity exists to improve the health of the nation by emphasizing one simple message: "Good health prevents AIDS." This is a message all could live with, and might go a long way to help reduce the incidence of STDs, drug use, and anal sexual practices which are the main causes of HIV transmission.

Instead, we have allowed a combination of ignorance and the influence of a variety of special interest groups to create a vast public paranoia among the healthy heterosexuals who represent most of the population and who have little or no risk of HIV infection.

We have permitted the gay rights activists to convince the public that "we are all at risk for AIDS" (even though the risk for most is too low to be of rational concern, if it exists at all).

We have allowed ourselves to become convinced that multiple sexual partners and the "one night stand" puts us at increased risk of HIV infection (even though it now is clear that this generally is not true).

As a justification for AIDS education in the schools, we have claimed that there is an "explosion" of AIDS cases among young people (there is not - in fact the number of AIDS cases reported by the CDC actually declined from 1990 to 1992 for the age group 13-24, at a time when other age groups were showing an increase!).

We have engaged in endless debates as to whether we should preach condoms or abstinence to our young people (even though neither will have a significant impact on the spread of HIV).

In order to bring a more balanced view of the AIDS epidemic to the heterosexual population, the following should be done instead:

1. Try to educate the public that there is a vast difference between what is theoretically possible and what is probable enough to be of concern. More than ever before, we need a concerted effort to educate the public about risk levels, in order to bring some rational thinking in public attitudes about AIDS.

2. Emphasize the generally low efficiency of heterosexual transmission in most cases, and the fact that few heterosexuals not involved with IV drugs ever become infected. The statement that "everyone is at risk" may be literally true, in the same sense that men are at risk of developing breast cancer, or people on the ground are at risk of being killed in a plane crash. But the statement implies an equal risk for all, which is far from the truth.

3. Focus heterosexual AIDS education for school children more sharply. There are those who want to use the AIDS epidemic to try to scare all young people into abstinence, in order to reduce unwanted pregnancies and the transmission of other STDs. The objective is commendable; however, falsifying the facts doesn't work in a free society. Ultimately, it destroys the credibility of those on whom the young people should be able to rely for help. Instead, the need to avoid sexual activity with those who use IV drugs (and of course anyone else known or suspected to be HIV-positive) should be emphasized. By making the drug users the pariahs of the teenage community, not only would AIDS education be correctly focused, but gains probably could be made in the war against drugs as well.

4. Emphasize the importance of prompt treatment of other STDs. The paper by Holmberg et al., referred to earlier, lists genital ulcerative diseases, including herpes and syphilis, as the only unquestioned cofactors in host susceptibility to HIV infection. In 1988, black women, who have a much higher rate of heterosexually transmitted AIDS than white women, had a rate of gonorrhea 21 times as great as white women. Similarly, black males, who also have a much higher rate of heterosexually transmitted AIDS than white males, had rates of early syphilis 25 times as high as white males. For black women, the rate of early syphilis was 31 times as great as for white women. Finally, rates of STDs in Africa, where heterosexual contact is considered to be the primary means of transmission of HIV, are believed to be far higher than in the U.S. So the key to reducing the heterosexual transmission of HIV in the U.S. may well involve control of the spread of other STDs, so as to reduce host susceptibility.

5. Stop emphasizing reducing the number of sexual partners as a means of reducing heterosexually transmitted AIDS. Most heterosexuals that get HIV from sexual intercourse do so from their primary sexual partner. Monogamy has little value in reducing HIV infections, and emphasizing it takes the focus away from the real ways in which transmission of HIV can be significantly reduced.

6. Better focus the need for using condoms. As was the case before the AIDS epidemic, for some they are useful in reducing the risk of pregnancy and STDs. However, for those who can avoid the risks of pregnancy in other ways, and for whom other STDs are rare, condoms provide little benefit, and detract from the love making process.

7. Better educate health care and government officials, who still have many misunderstandings about the epidemic and what needs (and doesn't need) to be done to control it's spread.

8. Most important of all, emphasize the message that "Good Health Prevents AIDS". As more facts become available about the nature of AIDS and other immune system disorders, it is becoming increasingly apparent that those who are in good health and who are not engaging in activities which are damaging their immune systems have little to worry about with regard to AIDS.


Effect of Transmission Efficiency on Proportion of Transmissions from Primary Partner

Let us assume that there are three types of heterosexuals: "monogamous", "semi-monogamous", and "multiple partners". "Monogamous" persons are those who have a sexual relationship with only one partner. "Semi-monogamous" persons are those who have a primary sexual partner, but who also have some sexual activity with others. Those who are identified as having "multiple partners" have sexual activity with a number of people, no one of whom can be called a primary partner.

The number of monogamous people to become infected with HIV in a given period of time can be expressed by the following formula:

Vm = Nm x im x [1 - (1 - p)n]


Vm = the number of monogamous people to become infected during the period.

Nm = the total number of monogamous people in the population.

im = the probability for monogamous people that one's sexual partner is infected with HIV.

p = the probability of becoming infected from a single act of sex with an infected partner.

n = the number of sexual acts during the period.

The number of people with multiple partners to become infected with HIV in a given period of time can be expressed by the following formula:

Vp = Np x {1 - [1 - (ip x p)]n}


Vp = the number of people with multiple partners to become infected with HIV during the period.

Np = the total number of people with multiple partners in the population.

ip = the probability for people with multiple partners that one's sexual partner is infected with HIV.

The remaining symbols are as previously defined.

The number of semi-monogamous people to become infected with HIV in a given period of time can be expressed by the following formula:

Vs = Ns x {1 - [1 - is x (1 - (1 - p)nm)] x [1 - (is xp)]np}


Vs = the number of semi-monogamous people to become infected with HIV during the period.

Ns = the total number of semi-monogamous people in the population.

is = the probability for semi-monogamous people that one's sexual partner is infected with HIV.

nm = the number of sexual acts engaged in with one's primary sexual partner during the period.

np = the number of sexual acts engaged in with people other than one's primary sexual partner during the period.

Finally, the proportion of total HIV infections caused by sexual relations with one's primary partner is as follows:

Ns x {1 - [1 - is x (1 - (1 - p)nm)]} + Vm

Vm + Vs + Vp

To examine the effect of the efficiency of the transmission of HIV on the proportion of heterosexual infections coming from primary partners, it is necessary to make certain assumptions. For the purpose of this analysis, we initially will assume the following:

1. The total number of sexual acts (n) for each person in the period is 200.

2. The probabilities that one's sexual partner is HIV+ (im, is, and ip) are all assumed to be 0.1%.

3. The distribution of people among the three categories is: monogamous, 60%; semi-monogamous, 36%; and multiple partners, 4%.

4. For those in the semi-monogamous category, the proportion of sexual acts with persons other than their primary partner was 10%.

The number of people in the total population does not actually affect the distribution of HIV infections between the three groups, although it does of course affect the number of infections.

The following table shows the effect of various levels of efficiency of transmission on the proportion of infections arising from sexual activity with one's primary partner, based on the above formulae and assumptions.

Percent of Infections from Primary Partner

Prob. of Transmission per Act

Percent of Total Infections Percent of Infect. from Primary Part.

Monogamous Semi-monog. Mult. Part.

0.5 9.1% 32.8% 58.0% 14.6%

0.2 18.5 33.2 48.3 29.6

0.05 39.0 35.1 25.9 62.4

0.02 50.2 36.2 13.6 80.3

0.005 57.6 36.3 6.1 91.2

0.002 59.1 36.1 4.8 93.1

0.00125 59.4 36.1 4.5 93.5

0.000625 59.7 36.0 4.2 93.9

0.0001 60.0 36.0 4.0 94.1

The table shows that for a disease that is easily transmitted by sexual activity, a high proportion of transmissions will occur from sexual activity with someone other than the primary partner. However, as the efficiency decreases, the proportion of transmissions that occur from sexual activity with the primary partner increases. For the efficiencies typical of heterosexual transmission of HIV, about 94% of the transmissions would be from the primary sexual partner.

The figures are somewhat dependent on the assumptions.

Of particular importance is the assumed distribution of people among the three categories. There is no way of knowing precisely what portion of heterosexuals are monogamous, what portion are semi-monogamous, and what portion should be considered to have multiple partners, without any one primary partner. Even if the distribution were known for the population as a whole, it could well differ for those persons who are more likely to have sexual contact with HIV+ partners.

However, there are two references which are somewhat helpful. In the article titled "The Study of Sexual Behavior in Relation to the Transmission of Human Immunodeficiency Virus", by researchers at the Kinsey Institute for Research in Sex, Gender, and Reproduction, published in the November, 1988 issue of American Psychologist, the following estimate is made of the degree of extramarital sexual relations:

"Based on six data sets, we estimate that 37% (range = 26-50%) of husbands have had at least one additional sexual partner during marriage. In a study of men over 50 years old, 23% of the respondents said that they had had extramarital sexual interaction since the age of 50 (Brecher, 1984). The estimate for wives' extramarital sexual relations, based on nine studies, is 29% (range = 20-54%)."

Another study, done by the Center for Health Affairs in Chevy Chase, Maryland, showed the following percentages of respondents admitting to four or more heterosexual partners:

  • Age 16-24 10.7%
  • Age 25-34 4.2%
  • Age 35+ 2.4%
  • These studies suggest to this author that the assumption of 60% monogamous, 36% semi-monogamous (with 10% of their sex with other than primary partners), and 4% multiple partners is a fairly reasonable depiction of the distribution of sexual habits of heterosexuals, particularly if the effect of the greater use of condoms by those engaging in sexual activity with other than their primary partner is considered.


    Comparison of Risk Levels for Multiple vs. Single Partners

    For homosexuals sexual activity with multiple partners significantly increases an already relatively high risk. However, for heterosexuals the risk remains about the same for any reasonable number of partners. The following table summarizes the risk levels for these two groups:

    Risk Ratio: Multiple Partner vs. Single Partner

    Heterosexual Men Heterosexual Women

    Number of Homosexual Partners Partners Sexual Acts

    Men Not HiRisk IVDU Not HiRisk IVDU

    20 1.08 1.01 1.01 1.01 1.01

    50 1.21 1.03 1.02 1.03 1.02

    100 1.45 1.06 1.03 1.06 1.03

    200 1.95 1.13 1.06 1.13 1.06

    500 3.37 1.34 1.16 1.34 1.16

    For monogamous relationships, the probability of HIV infection from a given number of sexual acts was determined by the formula:

    i x [1 - (1 - p)n]


    i = the probability that one's sexual partner is infected.

    p = the probability of infection from a single act of sex with an infected partner.

    n = the number of sexual acts during the period.

    For the person with multiple partners, the probability of getting an HIV infection from a given number of sexual acts is as follows, assuming that one's partners are chosen at random from among the pool of persons in the risk group (i.e., that there is not some element of monogamy involved):

    1 - [1 - (i x p)]n

    The table demonstrates that, even for as many as 100 different sexual partners, there is only a 6% increase in risk for heterosexuals, as compared with the same amount of sexual activity with one partner. By comparison, there is a 45% increase for homosexual men. The additional risk for homosexuals is further increased by four other factors:

    1. The average risk of infection even from a single homosexual act is much greater than that from a single act of vaginal intercourse if the heterosexual's partner is not an IV drug user, and is several times greater even if the heterosexual's partner is an IV drug user. Therefore, a 45% increase is very large in absolute terms, as compared with the risk for heterosexuals.

    2. The number of sexual partners that some of the more promiscuous homosexual men have had is generally believed to be much greater than that for heterosexuals (except for prostitutes).

    3. Because of the greater risks of promiscuity, the sexual partners of the homosexual man who is promiscuous are more likely to be infected than those of the less promiscuous homosexual.

    4. Finally, the majority of infected homosexuals became HIV-positive through sexual activity. By contrast, the majority of infected heterosexuals became HIV-positive through IV drug use or blood transfusions. The result is that restricting one's sexual activity is far more important for homosexuals than for heterosexuals. *


    1. "HIV/AIDS Surveillance Report, U.S. AIDS Cases Reported through December, 1992". Published by the U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, Atlanta, GA 30333 (February 1993).

    2. "AIDS Public Information Data Set". Published semi-annually by the Centers for Disease Control, U.S. Department of Health and Human Services.

    3. "Lying to Military Physicians about Risk Factors for HIV Infection", by J.J. Potterat, L. Phillips, and J.B. Muth. Journal of the American Medical Association, Vol 258 p. 1727 (1987).

    4. "Accurate Determination of Risk Behavior of Persons With AIDS", by A.M. Lekatsas, R. O'Donnel, J. Walker et al. Presented at the Third International Conference on AIDS, June 2, 1987, Washington DC.

    5. "Vital Statistics of the United States", by the National Center for Health Statistics. 1990 Statistical Abstract of the United States, p. 174.

    6. Ibid, p. 606.

    7. "Living Against the Odds", presented on National Public Television in April 1990.

    8. "Male-to=Female Transmission of Human Immunodeficiency Virus", by Nancy Padian, PhD; Linda Marquis, Donald P. Francis, MD, DSc; Robert E. Anderson, MD; George W. Rutherford, MD; Paul M. O'Malley; Warren Winkelstein, Jr., MD, MPH. Journal of the American Medical Association, Vol 258, No 6 (August 14, 1987).

    9. "Heterosexually Acquired HTLV-III/LAV Disease (AIDS-Related Complex and AIDS). Epidemiologic Evidence for Female-to-Male Transmission", by Robert R. Redfield, MD; Philip D. Markham, PhD;

    Syed Zaki Salahuddin, MS; D. Craig Wright, MD; M. G. Sarngadharan, PhD; Robert C. Gallo, MD. Journal of the American Medical Association, Vol 254 No 15 (Oct 18, 1985).

    10. "Preventing the Heterosexual Spread of AIDS - Are We Giving Our Patients the Best Advice?", by Norman Hearst, MD, MPH, and Stephen B. Hulley, MD, MPH. Journal of the American Medical Association, Vol 259 No 16 (April 22/29, 1988).

    11. "Female-to-Male Transmission of Human Immunodeficiency Virus", by Nancy S. Padian, PhD; Stephen C. Shiboski, PhD; and Nicholas P. Jewell, PhD. Journal of the American Medical Association, Vol 266, No 12 (Sep 25, 1991).

    12. "Biologic Factors in the Sexual Transmission of Human Immunodeficiency Virus", by Scott D. Holmberg, C. Robert Horsburgh, Jr., John W. Ward, and Harold W. Jaffe. The Journal of Infectious Diseases, Vol 160 No 1 (July 1989).

    13. "Heterosexual Transmission of HIV Infection", by N. H. Steigbigel, D.W. Maude, C.J. Feiner, and C.A. Harris. Abstract 4057 from Program and Abstracts of the Fourth International Conference on AIDS, Stockholm, Sweden. Swedish Ministry of Health and Social Affairs (1988).

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