Medicine: The Deadly Spread of AIDS

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The search for a common thread among these widely diverse groups has confounded researchers from coast to coast. When AIDS was confined to the gay community, says Curran, "our efforts were concentrated on trying to dissect out life-style differences." Various sexual practices and the use of amyl nitrite "poppers," inhalants widely used by homosexuals to enhance orgasm, were among the subjects investigated. The life-style theory does not, however, explain the emergence of AIDS in nongay populations. Most researchers now believe that an infectious agent is involved in AIDS. This agent is probably transmissible in a variety of ways, through lesions caused by anogenital sex, for example, or by dirty hypodermic needles. The hemophiliac cases raise the frightening possibility that it can also be transferred through blood transfusions. One model for such an agent is the hepatitis B virus, which commonly infects homosexuals, drug addicts, donor-blood recipients and, partly because of poor sanitary conditions, most Haitians. A few researchers speculate that the AIDS agent may have originated in Haiti and been sexually transmitted to American homosexuals vacationing there.

The narrow geographic distribution of AIDS further supports the transmissible-agent theory. Half the cases occurred in New York, 20% in California. More to the point, AIDS has been traced from sexual partner to partner. In one Los Angeles study, nine out of 13 patients had had sexual contact with one another. In San Francisco, six pairs of "roommates" have been stricken with Kaposi's sarcoma.

So far, efforts to isolate an AIDS bug have come to nothing. The CDC has cultured specimens from lymph nodes, urine, feces and blood of AIDS victims and then inoculated them into specially bred marmosets, at a cost of $25,000 for testing on each animal. Unfortunately, as Curran points out, "it is not known whether there is a transmissible agent, whether the patients we're studying harbor it, which body secretion may contain it, and whether marmosets are an appropriate species."

While some investigators delve into the question of AIDS transmission, others are exploring the nature of the disease. The type of immunosuppression found in AIDS patients appears to be unique, affecting white blood cells called T lymphocytes (T for thymus, which plays a role in their development). Certain of these cells help defend the body against viruses, foreign tissue (like organ transplants) and the growth of cancer cells. There are several types, including helper T cells, which promote the production of antibodies against foreign invaders, and suppressor T cells, which reduce antibody output. Healthy individuals have twice as many helpers as suppressors. In AIDS victims, the ratio is reversed; helper cells are depleted. No one knows what happens to these cells, but New York Immunologist Roger Enlow has a theory: "Just as hepatitis B virus preferentially attacks liver cells, it is probable and even likely to have a virus that at tacks helper T cells."