Back grey_arrow_rt.gif
 
 
Large drop reported in HIV cases in S.F. Feared second wave of infections appears to have crested
 
 
  SF Chronicle
Sabin Russell, Ilene Lelchuk,
Wednesday, July 20, 2005
 
In a rare piece of good news on AIDS, San Francisco health officials may revise downward their estimates of the number of new HIV infections each year after three new analyses suggested that the spread of the virus in the city's gay community has slowed substantially.
 
Since 2001, the city's highly regarded epidemiology team has held to an estimate that more than 1,000 city residents are newly infected with the AIDS virus each year.
 
But last month, a federal study of HIV among gay men in five U.S. cities found that new infections in San Francisco were occurring at about half the rate recorded four years ago.
 
"This one (CDC) study has been quite an eye opener for us," said Dr. Willi McFarland, epidemiologist for the San Francisco Department of Public Health's Office of AIDS.
 
The study by the national Centers for Disease Control and Prevention used survey methods considered state of the art in disease surveillance. Based on a sample of 365 gay men tested in the city, the study found that men were becoming infected at a rate of 1.2 percent per year.
 
San Francisco epidemiologists had previously estimated an infection rate of 2.2 percent.
 
The startling new finding prompted McFarland's office to analyze other sets of data often used by the city to track the course of the epidemic. Two of them -- information collected by the city's Stop AIDS Project, and surveys of infection rates at city clinics -- pointed to a similar downward trend in new HIV cases.
 
City officials therefore are expected to convene within a month a panel of experts to consider lowering San Francisco's official estimate of annual HIV infections -- which would signal that the feared second wave of the epidemic detected in 2000 has crested without a return to the ghastly infection rates of 8.5 percent in the early 1980s. By 1988, half the city's gay male population was infected.
 
"HIV incidence among men who have sex with men in San Francisco appears to be decreasing,'' said city health director Dr. Mitch Katz.
 
The reasons for the apparent decline in new HIV infections may take years to understand, but Katz said the most likely explanation is that effective AIDS drugs have lowered the level of virus in those men who are HIV-positive and still having unprotected sex. Another possibility is that gay men are increasingly reserving the most risky behaviors, such as anal intercourse without a condom, for partners who are of the same sero-status -- a practice known as "sero-sorting." For example, HIV-positive men who sero-sort would have unprotected sex only with HIV positive partners.
 
"The message is that, overall, prevention is working,'' Katz said.
 
Gauging HIV infection rates is a notoriously difficult task, and since the beginning of the epidemic, scientists have had to pool data from multiple sources to make an educated guess. No single study, such as the CDC survey released last month, will do.
 
At the forthcoming HIV "consensus conference" in San Francisco, experts will consider at least 11 different indicators that the city regularly uses to track the course of the epidemic.
 
It was such a consensus conference in 2001 that set the city's estimated HIV rate at 1,048 new infections per year. Prospects now appear good that the estimate will be substantially reduced.
 
Even if further analysis confirms a lower infection rate, McFarland remains cautious.
 
"The incidence rate is still too high," he said. "There is a lot more work to be done. It's ground we lost when (HIV) resurged in the first place."
 
The CDC study, conducted in five major cities, was based on interviews with more than 1,764 men contacted at bars and dance clubs, sex clubs and gyms, and on the streets and in parks and shops. Participants included gay men in San Francisco, Los Angeles, New York, Miami and Baltimore. In addition to volunteering for blood tests, they were asked about their partners, where they met them, their drug usage and other questions.
 
City health officials were heartened by a finding in the CDC study that among the five cities surveyed, San Francisco had the lowest rate of gay men who were infected but didn't know it at the time of the study.
 
In Baltimore, for example, a startling 40 percent of men participating in the study tested positive, and 62 percent of them did not know they were infected when they volunteered to be tested. In San Francisco, by contrast, 24 percent of participating men tested positive, and only 23 percent of those did not already know it.
 
Overall, researchers found that nearly half the men who tested positive in the survey did not know they were infected -- prompting calls for increased efforts to encourage people to get the test.
 
According to McFarland, the city was due for a new consensus conference anyway, since the last one took place four years ago. Data from the city's sexually transmitted disease clinics, where infection rates are expected to be high and were 5.4 percent in 2000, have fallen to 3.2 percent. At a clinic that provides anonymous testing services, rates have fallen from 3.9 percent to 2.8 percent.
 
Surveys by the Stop AIDS Project show a significant trend toward greater use of sero-sorting, which reduces but does not eliminate the risk of transmitting or acquiring HIV. Since 2001, the percentage of HIV-positive men reporting having unprotected sex with HIV-negative men, or men whose status is unknown, has fallen to 21 percent from 31 percent. The percentage of HIV- negative men who have had unprotected sex with positive men, or men of unknown sero-status, has fallen to 4 percent from 20 percent.
 
Stop AIDS spokesman Jason Riggs attributed the apparent decline in HIV infection rates to efforts that focus prevention messages on men who are already positive, encouraging behaviors such as sero-sorting. Programs to discourage use of crystal methamphetamine may also be paying off in San Francisco, he said.
 
Studies show that men who use the drug are three to four times more likely to become HIV-positive. The drug promotes "disinhibition," causing users to be more likely to engage in risky sex.
 
"If we can reduce the numbers of men using and abusing crystal methamphetamine, we can reduce the number of new infections significantly,'' Riggs said.
 
 
 
 
  icon paper stack View Older Articles   Back to Top   www.natap.org