Just over a quarter of HIV-positive individuals who had unprotected sex with partners who were either HIV-negative or of unknown HIV status, had drug resistant virus in a study conducted by US and Canadian researchers. However the researchers also found that the vast majority of unprotected sex between drug resistant individuals and parters of the oppositive or unknown HIV status was confined to three individuals in the cohort. The study published on-line in the eJournal of the International AIDS Society investigators from the OPTIONS study, which looked at the HIV transmission risk behaviours of people receiving HIV care, found that 28% of all instances of unprotected sex reported in the study involved individuals with resistant virus.
In the US, Canada and other countries where there is access to antiretroviral therapy, the number of incident HIV infections involving primary drug resistance has increased. It’s thought that between 10 - 15% of all new HIV cases in the US and Canada involve primary drug resistance and a similar rate of prinary resistance has been seen in the UK and other richer countries. Expanding use of anti-HIV therapy and ongoing sexual risk behaviour involving HIV-positive individuals provide the background to the transmission of resistant virus.
US and Canadian investigators examined the sexual behaviour was of 393 patients with or without drug-resistant HIV and to see if there were any factors associated with unprotected sex whilst having drug-resistant HIV. Individuals were enrolled in the study for two years between 2000 - 2003 and completed questionnaires about their sexual behaviour in the previous three months at six monthly intervals.
The definition of unprotected sex was rather broad as it included not only anal or vaginal sex without a condom, but also oral sex when condoms weren’t used. The number of instances of unprotected oral sex, which carries a much lower risk of HIV transmission than unprotected penetrative sex, are not provided. The investigators’ findings should therefore be viewed with some caution. The study population was largely heterosexual (79%), with 44% being women and 11% men who contracted HIV from sex with other men.
Approximately two-thirds of individuals (250) reported sexual activity during the course of the study, and of these 250 inviduals 112 (45%) reported unprotected sex. Just unde r3,500 risk event involving 354 partners were recorded.
The investigators then looked at the risk of HIV transmission occuring as a consequence of these episodes of unprotected sex. Of the 112 patients engaging in unprotected sex, 60 (54%) had a plasma viral load above 1,500 copies/ml. This is thought to be the lower limit needed for there to be a significant risk of HIV transmission occuring. Median viral load amongst these individuals was 27,000 copies/ml.
Attention was then turned to unprotected sex involving individuals with drug-resistant HIV. Of the 112 patients reporting any unprotected sex, 35 (31%) had unprotected sex. Most of the individuals (24) had resistance to one class of antiretroviral drugs; but 13 had resistance to two classes and two patients had triple-class resistance. Median plasma viral load for patients with drug resistance was 14,000 copies/ml, well above the threshold needed for a risk of HIV transmission.
The investigators estimated that 73 individuals were exposed to drug-resistant virus, and of these 58 were either HIV-negative or of unknown HIV status.
A small number of individuals with drug-resistant HIV appear to have been responsbile for most of the instances of unprotected sex with HIV-negative partners or partners whose HIV status was unknown. The investigators calculated that just three individuals were responsible for 85% of such episodes.
“The results of this study support the development, testing, and development of targeted prevention and risk reduction strategies”, conclude the investigators. The provision of such interventions in a clinical setting may, the study’s authors suggest, be facilitated by “the frequent contacts and trusting relationships that occur between clinicians and their patients.”
Kozal MJ et al. A population-based and longitudinal study of sexual behaviour and multidrug-resistant HIV among patients in a clinical setting. eJournal of the International AIDS Society 8: 72.