THE HIV NON-SURGE

The San Francisco Public Health Department study which alleges a sharp increase in HIV infection in that city among gay men has just been released. I’m grateful to the researchers for getting me a copy. What that means, of course, is that all those news stories written last week were written by reporters with no access to the actual data! Go figure. What’s my read? There are six mini-studies of men seeking sex with men (gay and bisexual) that lead the researchers to their conclusion of soaring infection rates. I have to say that I’m unconvinced. It’s possible, but nothing in the report proves it. Only one study has a reasonably representative sample of young gay men between the ages of 21 and 29, randomly selected from neighborhoods where AIDS infection is highest in the city. But the sample size varies considerably over time. In 1994 – 95, for example, there were 660 men in the sample. In 1998 – 99, there were 322. In 1993 – 94, there were a mere 261. Unsurprisingly, the smallest samples show the greatest variation from the mean. In 1993, at the height of the safe-sex era, HIV-transmission is calculated as 2.7 percent. The next year, the rate plummeted to 1.4 percent. The researchers provide no reason for this shift, and it’s almost certainly a function of sample size. Last year’s incidence rate of 1.8 percent is certainly within the realm of the average of the last several years which is around 1.4 percent. The “doubling” scare is more a function of the freak low figure for 1997 – 98, for which again there is no explanation. And the numbers themselves are tiny – a mere three HIV seroconversions in 1997; a mere 9 in 1998 – 99. You’d be statistically right if you declared a tripling in HIV rates from such numbers. But you’d also be really silly to draw such a conclusion from a total of 12 cases.