Viruses typically cause disease shortly after infection, before the immune system of their host can respond. There is no other example of a viral pathogen which causes primary disease only after long and unpredictable latent periods, only in the presence of neutralizing antibodies, and in the virtual absence of gene expression, as HIV is said to do.

The number of HIV carriers in the U.S. has remained constant at one million since 1985, when widespread antibody testing was introduced, yet new viruses spread exponentially in a susceptible population.