Prevalence data from the serosurveillance system continue to reflect the widespread, yet extremely varied, distribution of HIV infection across demographic and geographic subgroups. From 1993–1997, the highest overall HIV prevalence rates were observed among persons who engage in high-risk sexual behavior, particularly MSM, and among IDUs entering DTCs. In all geographic regions and metropolitan areas, prevalence rates among MSM in participating STD clinics were high (overall unadjusted rate, 26%; range, 8%–39%). In contrast to HIV rates among MSM at STD clinics, prevalence among IDUs entering DTCs during the 5-year period were remarkably diverse by region and by metropolitan area (overall unadjusted rate, 18%; range, 1%–37%). Among heterosexual men and women who attended the STD clinics but who did not inject drugs, the overall unadjusted prevalence rate was 2.3%. In a pattern similar to that for IDUs, prevalence rates for these high-risk heterosexual patients differed greatly by region (0.3%–5.5%) (Figure 1, Tables 2 and 3).

Figure 1. Comparison of HIV Prevalence Among Men Who Have Sex With Men at Sexually Transmitted Disease Clinics and Injection Drug Users Entering Drug Treatment Centers, by Metropolitan Area, 1993–1997

Among youth populations in the serosurveillance system, HIV prevalence remained low. For patients at the five participating adolescent medicine clinics, the unadjusted clinic prevalence rate for the 5-year study period was 0.4%. Among Job Corps entrants, the overall unadjusted rate in all regions was less than 0.2%.

HIV prevalence was low among military applicants and first-time blood donors, populations in which high-risk persons were likely to have self-deferred. The overall unadjusted prevalence rate from 1993–1997 among military applicants was less than 0.04%. The lowest observed HIV prevalence of all the selected populations in this report was among first-time blood donors; prevalence for this group was 0.027% for men and 0.011% for women.

HIV prevalence continues to differ by race/ethnicity; rates are substantially higher among blacks in nearly every serosurveillance population. For example, overall unadjusted prevalence rates among MSM at STD clinics were 40% among blacks, 26% among Hispanics, and 21% among whites. Among heterosexual patients at these clinics, prevalence for race/ethnicity differed by region but remained relatively high among blacks in all regions. The highest overall prevalence for these high-risk heterosexuals was in the Northeast for blacks (4.3%) and Hispanics (4.0%) (Table 4).

For IDUs entering DTCs, the association between HIV prevalence and race/ethnicity differed considerably by region. In the Northeast, unadjusted prevalence rates were higher among IDUs who were black (42%) and Hispanic (38%) than among those who were white (17%). A similar pattern was observed in the South, where rates were higher among black IDUs (20%) and Hispanic IDUs (24%) than among white IDUs (6%). In the Midwest, prevalence was markedly higher among Hispanic IDUs (27%) than among black IDUs (11%) or white IDUs (6%). In the West, prevalence among black IDUs (11%) was considerably higher than among Hispanic IDUs (1%) or white IDUs (2%) (Table 4).

Prevalence was 6 times higher among black adolescent medicine clinic patients (0.6%) than among Hispanic (0.1%) and white patients (0.1%). The overall prevalence of 0.32% among black Job Corps entrants was 4 times that for Hispanics (0.08%) and more than 6 times that for whites (0.05%). Among military applicants, the overall prevalence among blacks (0.15%) was 5 times higher than among Hispanics (0.03%) and 15 times higher than among whites (0.01%) (Table 4).

In general, prevalence was higher among survey participants who were in the older age categories and, with the exception of Job Corps entrants, among those who were male. For most of the surveillance populations included in this report, prevalence by region, race/ethnicity, and age group either decreased or remained stable from 1993–1997.

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