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-Study Finds No Evidence of Sexually Transmitted HCV-

A study from the United Kingdom offers further evidence that hepatitis C virus might not be transmitted by sexual intercourse in heterosexual relationships.

Researcher R. Wyld and colleagues concluded that heterosexual transmission, if it happens at all, occurs only rarely and that HIV infection is not a cofactor for hepatitis C virus (HCV) transmission.

Although it is well-known that HCV infection can be spread easily by contact with infected blood, other possible routes of transmission are not fully understood.

Previous studies have examined the incidence of HCV among blood transfusion recipients, homosexual men, and hemophiliacs. Fewer studies have addressed transmission of the virus via heterosexual activity.

As part of a longitudinal study to examine the heterosexual transmission of HIV, Wyld et al. established a group of HIV positive injecting drug users (IDU) and their heterosexual partners, most of whom were in long, stable relationships ("Absence of Hepatitis C Virus Transmission but Frequent Transmission of HIV-1 from Sexual Contact with Doubly-Infected Individuals," Journal of Infection, September 1997;35:163-166).

The prospective study began in 1987 and retrospective data were collected from 1983. Both periods of study included a recording of sexual history. Blood samples were taken annually from each HIV infected subject, and at six-month intervals from their sexual partners for the duration of the study or until the relationship ended.

Data were obtained using a structured questionnaire designed specifically to investigate the heterosexual transmission of HIV. Both sexual partners were interviewed separately by one of two trained nurses, and information was recorded on contraception methods, conceptions, sexual practices, blood transfusion, intravenous drug use, and any other transmission risks. Contraceptive methods, including condom use and abstinence, were recorded in monthly time intervals.

If an independent risk factor for transmission was recorded, i.e., drug use, partners were excluded from the heterosexual cohort.

For the purposes of this study, the cohort was divided into two groups, the first comprising individuals with a longstanding stable partnership with no history of needle-sharing. The second group comprised those partnerships where needle-sharing drug abuse occurred between them or with others for at least part of the study period.

In 30 of the 61 couples included in the analysis, it was determined that their only potential exposure to infection was through sexual contact. Sexual contacts of HIV positive individuals were screened for antibody to HIV at six month intervals throughout the study period. Among the heterosexual group, 12 out of 30 individuals (40 percent) became infected with HIV at varying times during the relationship. In the drug-user group, 16 out of 31 (52 percent) became infected with HIV.

No cases of HCV infection were detected in the 30 people whose only risk exposure was heterosexual sex, compared to high rates of exposure (25 of 31 HCV conversions) in the drug using group.

"This study provides a direct comparison of the relative rates of HIV and HCV transmission from doubly-infected index patients," Wyld et al. wrote. "The striking finding in this study was the complete absence of HCV transmission in the heterosexual cohort over a combined 11-year study period, during which 12 subjects became infected with HIV-1. This is direct evidence that HCV is (at least) several times less infectious than HIV-1 by this route, and that even frequent, unprotected sexual intercourse apparently carries little risk to the contact.

"It is also of interest how incomplete HIV transmission is in an unprotected group of sexual partners over a prolonged exposure period. These findings add to the growing consensus from European and American studies that HCV is only rarely transmitted by sexual contact and that in contrast to earlier reports, HIV may not be a co-factor for HCV transmission. Whether it ever occurs remains uncertain."

Wyld et al. concluded that their findings are, "useful, somewhat reassuring, and an addition to the information base needed for counselling and inclusion in guidelines."

The corresponding author for this study is J.R. Robertson, Muirhouse Medical Group, 1 Muirhouse Avenue, Edinburgh EH4 4PL, United Kingdom.

- by Salynn Boyles, Senior Editor

AIDS Weekly Plus, November 10, 1997, News Section, pp. 30-31.

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