Current Trends Update: Acquired Immunodeficiency Syndrome in
the San Francisco Cohort Study, 1978-1985
Between 1978 and 1980, a cohort of approximately 6,875
homosexual
and bisexual men who had sought evaluation for sexually transmitted
diseases at the San Francisco (California) City Clinic was enrolled
in
a series of studies of the prevalence, incidence, and prevention of
hepatitis B virus infections (1,2). In 1981, six of the first 10
men
reported with acquired immunodeficiency syndrome (AIDS) in San
Francisco were discovered to be members of the City Clinic cohort.
Subsequently, the Department of Public Health and CDC began a study
of
cohort members for AIDS and for infections with human
T-lymphotropic
virus type III/ lymphadenopathy-associated virus (HTLV-III/LAV),
the
cause of AIDS.
In a representative sample of cohort members, prevalence of
antibody to HTLV-III/LAV, measured by an enzyme immunosorbent
assay
(EIA), increased from 4.5% in 1978 to 67.3% in 1984 (3). From
January
through August 1985, HTLV-III/LAV antibody prevalence further
increased to 73.1% (Figure 1). The number of AIDS cases reported
among cohort members increased from 166 in 1984 to 262 in August
1985
(Figure 2).
Thirty-one members of the sample who consented to have their
earliest specimens tested had antibody to HTLV-III/LAV at the time
they enrolled in studies between 1978-1980. By December 1984, two
(6.4%) (95% confidence bounds 0.8%-21.4%) had developed AIDS, and
eight (25.8%) had AIDS-related conditions, as defined elsewhere
(3).
Symptomatic infections with HTLV-III/LAV thus had occurred in 10
(32.2%) (95% confidence bounds 16.7%-51.4%) of the 31 men after a
follow-up period averaging 61 months. No further cases of AIDS
have
been reported in the 29 men through the first 8 months of 1985.
Sixty members of the cohort who were seronegative in 1984 were
tested again in 1985, an average of 14 months (range 9-18) after
their
last specimens were collected; nine (15.0%) were found to have
developed antibodies to HTLV-III/LAV. Five of the nine had reduced
their numbers of sexual partners since their last visit; two had
not
changed; and two had increased their numbers slightly. Each man
who
seroconverted had engaged in sexual activities that resulted in the
exchange of semen and other body fluids. Two seroconverters who
reported sexual exposures with only one steady partner since their
last negative test had engaged in receptive anal intercourse with
ejaculation by their respective partners.
Men who remained seronegative were not shown to differ
significantly in sexual practices from those who seroconverted, but
the number of seroconverters available for comparison is small.
Reported by D Echenberg, MD, G Rutherford, MD, P O'Malley, T
Bodecker,
San Francisco Dept of Public Health; AIDS Br, Div of Viral
Diseases,
Center for Infectious Diseases, CDC.
Editorial Note
Editorial Note: The cumulative incidence of AIDS in City Clinic
cohort members is now 3,825 per 100,000, the highest of any
reported
population (4,5). Almost three-quarters of cohort members now have
serologic evidence of HTLV-III/LAV infections. The long-term
prognoses for these men is unknown. The fact that two-thirds of
men
infected for over 5 years have not developed AIDS or AIDS-related
illness is an encouraging indication that infection with this virus
is
not necessarily followed by rapid development of symptoms and
death.
Studies from New York City, San Francisco, and elsewhere
suggest
that many gay men have changed their sexual lifestyles (5).
Between
1980 and 1983, rates of rectal and pharyngeal gonorrhea in men in
Manhattan decreased 59% (6). Surveys of self-reported behavior of
gay
men in San Francisco have shown decreases in both the average
number
of sexual partners and sexual practices known to transmit
HTLV-III/LAV
infection (7,8). However, as the prevalence of HTLV-III/LAV
infection
in a population increases, substantial changes in both the numbers
of
sexual partners and types of sexual practices will be necessary to
reduce the risk that susceptible gay men may become infected.
References
Schreeder MT, Thompson SE, Hadler SC, et al. Hepatitis B in
homosexual men: prevalence of infection and factors related to
transmission. J Infect Dis 1982;146:7-15.
Francis DP, Hadler SC, Thompson SE, et al. The prevention of
hepatitis B with vaccine. Report of the Centers for Disease
Control multi-center efficacy trial among homosexual men. Ann
Intern Med 1982;97:362-6.
Jaffe HW, Darrow WW, Echenberg DF, et al. The acquired
immunodeficiency syndrome in a cohort of homosexual men: a
six-year follow-up study. Ann Intern Med 1985;103:210-4.
Hardy AM, Allen JR, Morgan WM, Curran JW. The incidence rate
of
acquired immunodeficiency syndrome in selected populations.
JAMA
1985;253:215-20.
Curran JW, Morgan WM, Hardy AM, Jaffe HW, Darrow WW, Dowdle WR.
The epidemiology of AIDS: current status and future prospects.
Science 1985;229:1352-7.
CDC. Declining rates of rectal and pharyngeal gonorrhea among
males--New York City. MMWR 1984;33:295-7.
Bye L. Designing an effective AIDS prevention campaign
strategy
for San Francisco: results from the first probability sample
of
an urban gay male community. San Francisco, California:
Research
and Decisions Corporation, 1984.
McKusick ML, Horstman W, Coates TJ. AIDS and sexual behavior
reported by gay men in San Francisco. Am J Public Health
1985;75:493-6.
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