This information was collected from 4,697 high-risk HIV-negative men who have sex with men, who were enrolled at 56 clinical-trial sites in the U.S. for the 36-month trial. Overall, there were 2.8 HIV infections per 100 person-years -- already considered a high number. But amphetamine users had 4.5 infections per 100 person-years, hallucinogen users had 4.0, and poppers users had 3.6. In this high-risk cohort there were many more users of poppers than of the other two put together -- 2176 reported poppers use, vs. 901 amphetamines and 603 hallucinogens -- suggesting a potentially large impact on the spread of HIV. 

The drugs may be having this effect by making people more likely to take risks they would otherwise have avoided. Some drugs might also affect the immune system directly. In August 1999 AIDS Treatment News noted animal studies showing that exposure to "poppers" increased cancer growth(2) and bacterial growth(3), probably by suppressing the animals' natural immunity.

GR Newell

These products have been found to be profoundly immuno-suppressive for human lymphocytes in vitro... Recreational use of inhaled volatile nitrites is prevalent among male homosexuals and compounds have been suspected as possible co-factors in Kaposi's sarcoma associated with AIDS.

Our studies show that amyl nitrite strongly suppressed the segment of the immune system which normally protects individuals against Kaposi's sarcoma, Pneumocystis pneumonia, herpes virus, Candida, amebiasis, and a variety of other opportunistic infections. The upshot of this research is that persons using nitrite inhalants may be at risk for development of AIDS.

Dr. Harry Haverkos

The proven potential for cancer causing nitrosamine in bacon... is probably one-millionth of the dose from inhalation of poppers.

Dr. James Curran

It is possible that heavy use of nitrites... may contribute in some as yet undefined way to the development of Kaposi's sarcoma in those already infected with (HIV) or who have AIDS.

Harold Jaffe

We studied them early in the epidemic, with a question whether [poppers] were actually the cause of AIDS. Which of course they weren't. We were left with the question: Could they explain something like Kaposi's sarcoma? I personally think that is not the explanation but I don't think we can rule it out.