HIV-1 seroconversion rates among female commercial sex workers, Chiang Mai, Thailand: a multi cross-sectional study

Abstract

Objectives: To determine HIV seroconversion rates among female commercial sex workers (CSW) in Chiang Mai, Thailand.

Design: A three-round multi cross-sectional study was used at approximately 3-month intervals.

Methods: In December 1989, 38 brothels (60%) in Chiang Mai were randomly selected. All 518 female CSW in the brothels were interviewed about their sociodemographics, sexual practices, condom use, history of sexually transmitted diseases (STD) and other risk factors. Blood was tested for Venereal Disease Research Laboratory (VDRL)-reactivity and HIV-1 antibody. The same brothels, which were all still operating, were revisited in March and July 1990 and 431 and 320 CSW, respectively, were interviewed and blood-tested. Pelvic examination, cervical, urethral and rectal cultures for gonococcus were added to the study in March 1990, although rectal culture was dropped from the study in July 1990.

Results: There were 5.2% [95% confidence interval (CI), 4.1-10.6] and 3.6% (95% CI, 1.5-5.4) per woman-month HIV seroconversion rates for the December-March and March-July periods, respectively. Of the CSW, 71.6-77.0% reported histories of at lest one STD. Condom-use rates among these CSW were reported to be 85.8-91.8%. High rates of positive cervical (11.2-12.3%) and urethral (8.8-11.4%) cultures for gonococcus were also found in the CSW.

Conclusions: The fact that high HIV seroconversion rates and high STD prevalence rates occur despite high rates of reported condom use suggests that more aggressive education programs are needed in Thailand.

PIP: In Thailand, health workers interviewed and drew blood samples from 518 female prostitutes working out of 38 brothels in Chiang Mai in December, 1989. They revisited the brothels, which were all still operating, and surveyed 431 and 320 female commercial sex workers in March and July, 1990, respectively. Researchers aimed for this 3-round multi cross- sectional study to determine HIV seroconversion rates among female prostitutes. HIV seroprevalence rates were 35.7%, 37.8%, and 42.6% in December, 1989, and March and July, 1990, respectively. 48.5% and 52.5% of prostitutes available on the 2nd and 3rd rounds, respectively, were new recruits. Newly recruited workers had much lower HIV seroprevalence rates than those previously working in the brothels (between 1st and 2nd round, 25.4% vs. 49.5% and between 2nd and 3rd round, 37.7% vs. 48%; p .05). The estimated HIV seroconversion rates in the December-March interval was 5.2% and 3.6% for the March-July interval. Around 90% of the workers used contraception, particularly oral contraceptives. Most (60.2-64.4%) were no more than 20 years old and were of Thai origin. Most workers (71.6-77%) had a history of sexually transmitted diseases (STDs), especially gonorrhea (45.6-63.4%) and genital ulcers (45.3- 47.2%). Positive cervical and urethral cultures for gonococcus were high (11.2-12.3% and 8.8-11.4%, respectively). Most (85.8-91.8%) used condoms for last night sex services. The high HIV seroconversion rates and high STD rates, despite high condom use, coupled with a high turnover rate suggest the need for more aggressive education programs aiming for 100% condom use rate to control the transmission of HIV and other STDs among commercial sex workers in Thailand.