Heterosexual transmission studies
Similar Data Cast Doubt on Hepatitis-C, but not HIV

by Paul Philpott

No funded HIV/AIDS researcher has ever doubted that HIV can be transmitted via vaginal intercourse. Every study on this subject merely assumes that vaginal transmission explains all positive HIV tests among heterosexuals who deny having injected drugs or had rectal intercourse, and who lack histories of blood transfusions, hemophilia treatments, and maternal exposure.

A 1997 NIH-sponsored study of antibody testing for hepatitis C among married Japanese couples offers an example of the careful analysis absent from heterosexual HIV transmission studies (Tanaka, International Journal of Cancer 72: 50-55). Subjects married to positive partners were twice as likely to test positive themselves as subjects married to negative partners. Although this may have suggested to the authors the possibility that hep C might be transmitted coitally, they did not jump to conclusions. The authors were more impressed by another observation familiar to anyone who's read similar studies of heterosexual HIV transmission: most positive subjects had discordant relationships, meaning, their spouses tested negative.

All things considered, the authors (including two Harvard epidemiologists) concluded, "our results suggest that the clustering of hepatitis C virus... may not be attributable to heterosexual transmission."

Such reasoning never occurred to the authors of a 1990 study of HIV antibody testing among married Ziarians (Ryder, AIDS 4: 725-732). Although their study employed the same methodology as the Japanese hep C study and achieved similar results, the authors (including two from the CDC and one from the NIH) ignored the possibility that something besides vaginal transmission of HIV might explain their observations.

The first sentence of their abstract indicates the special dispensation from scientific scrutiny afforded HIV. The authors conducted the investigation "to better understand the reasons why up to 80% of all HIV-1 infections in Zaire, but less than 5% in North America and Europe, are acquired through heterosexual transmission." What makes them believe that heterosexual transmission accounts for these figures? Because they represent the fractions of positive testing people who deny homosexuality, drug injecting, and transfusions. The authors cite no previous experiments or studies demonstrating that HIV can be transmitted coitally.

No paper about HIV includes a statement like that which began the Japanese hep C study's abstract: "The heterosexual transmission of hepatitis C virus remains controversial..." Heterosexual transmission of HIV has never been controversial. It has never been tested, or for that matter, established. It has simply been assumed, a central tenet of the HIV model that governs every study of the subject.

Remarkably, the support for coital transmission in the hep C study is stronger than the support in the HIV study. Among study participants, heterosexual couples were about nine times more likely to have at least one partner positive for hep C than for HIV (44% versus 5.3%), and twice as likely to have both partners positive for hep C than for HIV (29% versus 15% among those with at least one positive partner).

Here's another way to think about these data. Of married people who test positive for hep C, 71% have spouses who test negative; for HIV, 85% have spouses who test negative. Do these really seem like coitally transmitted viruses?

Presumably the hep C investigators could assume heterosexual transmission and derive the sort of absurdly low transmission frequencies claimed for HIV. Instead they regard their data skeptically, in the scientific tradition.

Thanks to Mike McLane for calling these papers to our attention. McLane was senior lab manager for two molecular biology groups at Johns Hopkins Medical School from 1977 through 1989. He graduated magna cum laude from Washington and Lee University with a BS in biochemistry.