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The next clue was confusing. Immigrants from Haiti turned up with AIDS. Not only was this puzzling—many claimed they were neither homosexuals nor drug users—but the discovery raised special problems for the epidemiologists. Homosexuality is scorned in Haiti, and the victims were reluctant to talk about their sexual habits. The language barrier also played a role; it was hard for investigators to describe in Creole—the everyday patois of Haiti—the homosexual acts in question, particularly since the same word applies to both homosexuality and transvestism. Many of the immigrants were in the U.S. illegally, and thus understandably reluctant to talk to Government agents about anything.
The Haitian connection is still puzzling. The disease apparently broke out on the impoverished Caribbean isle in 1981, at about the same time as it did in the U.S. Some experts suspect that AIDS is caused by a newly introduced viral agent from Africa, where Kaposi's is common, and may have been transmitted by Haitians who once worked in Zaïre. Port-au-Prince has many popular gay bars, and the disease could have been brought back to the U.S. by visiting Americans—or taken to Haiti by Americans in the first place. Recent investigations suggest that the disease is probably transmitted in Haiti, much as it is in the U.S., by homosexual activity or by dirty needles, and that Haitians have no more propensity for the disease than victims in the U.S.
As the search and speculation went on, researchers in U.S. labs added their own clues: the blood of AIDS victims has an imbalance among the cells that help govern the production of antibodies. A normal immune system has twice as many helper Tcells, which stimulate the making of antibodies, as it does suppressor Tcells, which keep antibody production under control. In an AIDS victim, the ratio may be reversed. Often there are fewer cells of both types.
Based on what is known so far, two theories have emerged. One is that AIDS is caused by a specific agent, most probably a virus. "The infectious-agent hypothesis is much stronger than it was months ago," says Curran, reflecting the prevailing opinion at CDC. NIH Researcher Fauci, who staunchly believes that the culprit is a virus, has been collecting helper T-cells from AIDS victims to look for bits of viruses within their genetic codes. So far, however, this and other complex methods of detecting viruses have yielded nothing conclusive. Suspicion focuses on two viruses: one is a member of the herpes family called CMV; the other, called human T-cell leukemia virus, or HTLV, is linked to leukemia and lymphoma.
The other theory is that the immune system of AIDS victims is simply overpowered by the assault of a variety of infections. Both drug users and active homosexuals are continually bombarded by a gallery of illnesses. Repeated exposure to the herpes virus, or to sperm entering the blood after anal intercourse, can lead to elevated levels of suppressor Tcells. The immune system eventually is so badly altered that, as one researcher puts it, "the whole thing explodes." Other experts combine the two theories, speculating that a new virus may indeed be involved, but that it only takes hold when a combination of factors affects the potential victim, such as an imbalanced immune system or certain genetic characteristics.