FIGURE 3.1 Cumulative number of reported adult AIDS cases worldwide through late 1992. Map derived from data provided by the World Health Organization, 1993.

pneumonia (caused by a parasite called Pneumocystis carinii), and a rare skin cancer called Kaposi's sarcoma are some of the most common causes of death for people with AIDS in the United States. Other AIDS-related conditions include lymphoma and other cancers, systemic yeast infections, toxoplasmosis and other degenerative disorders of the nervous system, and an unexplainable wasting syndrome (see Table 3.1). If any one of these conditions in itself is not fatal, the cumulative effect of fighting off so many infections with an increasingly damaged immune system often is. In one sense the solution to the problem is clear. If science could find a way to lessen the immune-depleting effects of the virus, people with AIDS would not be so defenseless against opportunistic infections.

But this strategy is not as simple as it sounds. Once the virus infects an individual, the virus and immune system are locked in an intimate and paradoxical relationship. Following infection the virus becomes part of the immune system and in so doing undermines the very defenses that are supposed to fight it. Eliminating the virus therefore means turning the immune system against itself. And there lies another of the disease's ironies and scientific challenges.