Antiretroviral treatment decreases both HIV viral load in both blood and genital fluid. By reducing the infectiousness of HIV-positive people, HAART should reduce onward HIV transmission to HIV-negative individuals.
Community surveys of the sexual behaviour of men who have sex with men (MSM), carried out over the past five years, have shown that the availability of HAART may have increased sexual behaviours that lead to HIV transmission. HIV-positive gay men are less concerned about transmitting HIV and HIV-negative men are less concerned about contracting HIV. At the same time both groups have been shown to be more likely to engage in unsafe sex. The availability of HAART has increased the number of people with HIV who are engaging in unsafe behaviours.
In this month's American Journal of Public Health, researchers from San Francisco's Department of Public Health have drawn on a range of data including rates of gonorrhea at the county STD clinic, use of HAART, interviews with over 26,000 MSM to assess the effects of HAART on seroincidence among MSM in San Francisco, and to try to understand what impact changes in sexual behaviour may be having on HAART's ability to decrease HIV transmission.
AIDS incidence among MSM in San Francisco peaked in 1992 and declined thereafter. Death from AIDS declined dramatically between 1995 and 1999; this coincides with the increase in the use of HAART among men with AIDS from 4% in 1995 to 54% in 1999.
Annual interviews carried out with men show the percentage of men who reported always using condoms in the preceding 6 months declined from 70% in 1994 to 54% in 1999. Over the same period the percentage the percentage reporting both unprotected sex and multiple partners increased from 24% to 45%.
The increases in the rates of rectal gonorrhea seen between 1994 and 1999 (from 72 to 160 cases) among MSM in San Francisco serve as epidemiological confirmation of the reported rise in unsafe sexual activity. Inflammatory STIs raise the likelihood of HIV transmission; higher gonorrhea prevalence is likely to increase HIV transmission within the community.
Trends in HIV incidence among MSM who sought HIV testing at the publicly funded anonymous testing site in San Francisco (11, 347 men tested between 1996 to 1999) and men who were seen at the county STD clinic for sexual health screens (4669 men seen between 1995 and 1999) were determined using 2 ELISA tests, one a 'detuned' assay which can distinguish recent infection (within the past 129 days) from longer standing infection. Among men tested at the anonymous site between 1996 and 1999, the estimated annual incidence rate increased from 1.3% in 1997 to 4.2% in 1999. Though no increase in HIV incidence was seen among MSM using the STD clinic, it is worth noting that the baseline seroincidence rate was already high, at 5.3%. The San Francisco Young Men's Study also reported an increase in HIV incidence from 0.81% in the 1997-1998 wave to 1.8% in the 1998-1999 wave.
A recently published theoretical model postulated that HAART's effect of decreasing HIV transmission could be cancelled out by an increase in unsafe sex of only 10%. This study found a greater than 10% increase in unsafe sex and the authors suggested that "it is not surprising that there was no decrease in HIV incidence…despite the HAART use."
Findings from another study in San Francisco, published last year which linked the AIDS registry with the STD (sexually transmitted disease) registry clearly illustrated that MSM with AIDS who were treated with HAART were more likely to acquire an STD than men not treated with HAART.
In last Friday's Los Angeles Times, Dr Jeffrey Klausner, director of sexually transmitted disease control for San Francisco warned that the recreational use of Viagra with other drugs by MSM is leading to risky sexual behaviour and increasing the likelihood of STI (sexually transmitted infection) transmission. He cites data from a soon to be published study of 844 men who use San Francisco's STD clinics. The study found that MSM were more than four times more likely than heterosexual men to use Viagra. The combination of Viagra and recreational drugs "lessens their resolve to use condoms," he argued. In total, 43% of the 108 men who had used Viagra had mixed the drug with ecstasy and one third had mixed it with methamphetamine.
Whilst this study has been unable to definitively show a causal relationship between availability of HAART, increased risk behaviour and flat or increasing seroincidence, the implication is that the availability of HAART has resulted in rates of unsafe sexual behaviour equal to or greater than the beneficial impact of HAART on per contact HIV transmission.
The authors suggested there is a need for MSM-focused prevention campaigns that take into account changes in perceived risk of HIV owing to HAART.
Katz M et al. Impact of highly active antiretroviral treatment on HIV seroincidence among men who have sex with men: San Francisco. American Journal of Public Health March 2002, Vol92, No. 3.
Blower SM et al. A tale of two futures: HIV and antiretroviral therapy in San Francisco. Science. 2000;287:650-654.
Scheer S et al. Effect of highly active antiretroviral therapy on diagnoses of sexually transmitted diseases in people with AIDS. Lancet 2001; 357:432-435.
Ornstein C. Warning on Viagra's role in STDs is requested. Los Angeles Times, 15 March 2002.