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.