Natural History of a Modern Plague

In late 1981 and early 1982, physicians from large cities in the United States began reporting to the Centers for Disease Control and Prevention cases of formerly rare infections in otherwise healthy young men. Some of the infections were prevalent in the general population, such as herpes simplex and cytomegalovirus, but in these young men were unusually severe. Oddly, some of the infections were caused by organisms known to infect only nonhuman animals. Other infections, particularly pneumonia caused by the microorganism Pneumocystis carinii and cancer, Kaposi's sarcoma, were known only in individuals whose immune systems were suppressed.

The bodies of the sick young men had become nesting places for all types of infectious agents, including viruses, bacteria, protozoans, and fungi. The infections were opportunistic, which means that they take advantage of a weakened immune system.

As the infections spread, a portrait of a lethal disease emerged. Acquired immunodeficiency syndrome, or AIDS, starts with recurrent fever, weakness, and weight loss. Then usually after a relatively healthy period, infections begin. Many patients die within 2 or 3 years of symptom onset, but the virus that causes AIDS can be present for a decade or longer before a person feels ill. Five percent of infected people have remained healthy for more than 15 years.

Scientists and physicians united to identify the source of the outbreak of infections. Attention turned first to the sufferers. What did they have in common? All had had blood contact with another AIDS patient. Many in the United States and Europe were homosexual men who transferred the infections through fragile rectal tissues during anal intercourse. Intravenous drug users spread AIDS by sharing needles. A growing AIDS population includes children who acquired the disease before or during birth from infected mothers. Today, worldwide, the most common mode of transmission is heterosexual intercourse.

Some people acquired AIDS from HIV-tainted blood transfused before 1985, when stricter blood banking precautions began. Many people with hemophilia were infected when they received blood products pooled from many donors. The toll on people with hemophilia has been staggering--90% of those who used clotting factors several times a month have AIDS, as do 70% of those who have ever received clotting factors. Today, half of all people with hemophilia are infected with HIV. Blood samples meticulously stores from people with hemophilia since the mid-1970s have greatly aided researchers in tracing the birth of the epidemic.

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