[The prevalence of human immunodeficiency virus infection in intravenous drug users in Valencia (1987-1991)]

60.8% of cases of AIDS reported in Valencia through 1991 were in intravenous (iv) drug users. Prevalence rates in studies conducted during 1985-90 have generally exceeded 50%. The major exception was a 1989 study by the National Drug Plan on a sample of iv drug users seeking outpatient treatment which found a prevalence of 41%. Differences in prevalence estimates are attributable mainly to differences in the survey population. But few studies have been done on drug users who voluntarily seek testing or on trends in infection rates over time. 2794 iv drug users attending 3 HIV information and prevention centers in the cities of Valencia Alicante and Castellon between September 1987 and March 1991 were studied. 2694 were tested using an enzyme immunoanalysis method with positive results confirmed by Western blot. Average age of those tested was 25.1 years. 698 were female and 2094 male. The 100 drug users who were not tested after counseling showed no statistically significant differences in age sex or educational level. Subjects were interviewed using a structured questionnaire on their sociodemographic characteristics sexual practices drug use and condom use. 1344 of the 2694 tested were seropositive with a global prevalence of 49.9% and 95% confidence intervals of 48.1%-51.7%. Prevalence rates in individual cities ranged from 55.3% in Valencia to 43.7% in Alicante and 41.3% in Castellon. A declining trend in prevalence was noted over the 5 years although when results were stratified by cities the decline was apparent only in Alicante and Castellon. Prevalence was almost identical for men and women but prevalence varied by age from 35.3% for those under 20 to 59.5% for those over 29. The average age was 25.9 for seropositive vs. 24.2 for seronegative subjects. 16.9% of the total sample reported sharing needles but the proportion declined from 27.7% in 1987 to 2.8% in 1991. 1575 of the 2794 persons treated reported they had a stable sexual partner. 70% of women vs. 53.2% of men reported a stable sexual relationship. Among those with stable sex partners 75% of the women and 29.4% of the men reported that the partner was also an iv drug user. 17.8% of the sample reported practicing anal intercourse; 85.9% of these 497 persons stated they never used condoms. 61.6% of those practicing vaginal intercourse reported never using condoms and only 26.1% did so regularly or always. Frequencies of condom use during different sexual practices remained stable over the 5 years of the study.