Most of the sex engaged in by a sample of over 3700 HIV-positive Americans over a three month period did not carry a risk of HIV transmission, according to a study published in the August 15th edition of the Journal of Acquired Immune Deficiency Syndromes. However, investigators found that 15% of gay men, 19% of heterosexual women, and 13% of heterosexual men infected with HIV had unprotected anal or vaginal sex with an HIV-negative partner (or a partner whose HIV status they did not know), and that this could have led to over 30 new infections.
A number of studies have found that approximately a third of HIV-positive individuals have unprotected sex after their HIV diagnosis. However, these studies have several limitations: they are often based on a small sample in a single geographical site, they have tended to focus on gay men, have regarded oral sex as a major HIV risk activity, and have not considered the impact of HAART on infectiousness.
Accordingly, US investigators asked a total of 3,723 HIV-positive individuals living in four large US cities about the type of sex they had had with their last five sexual partners over a three-month period. Study participants were asked if they had been sexually active. They were divided according to their sexual orientation and asked how many times anal or vaginal sex took place, the number of times condoms were used, if they knew their partners’ HIV status, and if they disclosed their HIV status to their partners. Individuals were also asked if the people they were having sex with were primary or casual partners, and gay men were asked to say if they were the insertive or receptive partner during anal sex.
The investigators constructed a mathematical model to predict how many new HIV infections the risk activity of the study population would have caused.
Individuals were recruited from clinics and HIV community-based agencies in Los Angeles, Milwaukee, New York and San Francisco between summer 2000 and early 2002.
A total of 1,918 individuals were gay men, 978 were women and 827 were heterosexual men. Three quarters of heterosexual men and women and 81% of gay men had been sexually active in the preceding three months. The mean number of sexual partners during this period was 5.8 for gay men, and 1.7 for heterosexual men and women.
Similar proportions of gay men and heterosexual men and women reported sex with an HIV-negative partner or a partner whose HIV status was unknown to them (49% gay men, 44.1% heterosexual women, 44% heterosexual men).
Three quarters of heterosexual men and women said that they had had vaginal sex, and 15% of heterosexuals also reported anal sex. Just under 50% of gay men (49.4%) had had insertive anal sex, and 52.6% had had receptive anal sex.
Unprotected sexual behaviour was widely reported. In total, 44.7% of gay men said that they had had anal sex without a condom, and 36.5% of women and 34% of heterosexual men also reported unprotected vaginal or anal sex.
However, most of this unprotected sexual activity was taking place with other HIV-positive partners. Only 15.6% of gay men, 19% of women and 13.1% of heterosexual men said that they had had unprotected sex with a partner of a different or unknown HIV status.
The gay men who reported unprotected anal sex with an HIV-negative partner, or partner of unknown status, did so on a mean of ten occasions. For heterosexual women the mean was 27.7 occasions and for heterosexual men the mean number of occasions was 19.3.
Fewer than half of gay men (47.7%) said that they had disclosed their HIV status to their partners who were HIV-negative or of unknown status prior to having unprotected anal sex. Almost two-thirds of women (68.6%) and heterosexual men (62.9%) said they disclosed to partners who were HIV-negative or of unknown status prior to having unprotected penetrative sex.
The investigators calculated that in the three months of sexual behaviour examined in this study, a total of 30.4 new HIV infections would have resulted from the unprotected sexual activities of the study population. This model took into consideration various suggestions about the effectiveness of HAART at reducing the infectiousness of HIV-positive individuals.
“More than half of [gay men] and approximately two thirds of women and heterosexual men did not report engaging in unprotected vaginal or anal intercourse with any of their recent partners. Among those who did…more than two thirds of unprotected acts occurred with HIV-positive partners. These findings are heartening because they indicate that most persons aware of their own HIV infection refrain from sexual activities likely to transmit the virus to others,” write the investigators.
However, their believe that their findings do have some public health implications, particularly as 19% of women, 15.6% of gay men and 13.1% of heterosexual men had unprotected penetrative sex with a partner who was HIV-negative or of unknown HIV status. The investigators calculated that this level of risky behaviour would result in 30 new HIV infections in the three-month period of sexual activity studied. Over a ten-year period this would mean 671 new infections.
The investigators believe that their findings “underscore the need to integrate ongoing HIV risk reduction counseling better within medical and other care programs serving persons living with HIV infection.”
Weinhardt LS et al. HIV transmission risk behaviour among men and women living in 4 cities in the United States. J Acquir Immune Defic Syndr 36: 1057-1066, 2004.