Risk factors for HIV-1 transmission from HIV-seropositive male blood donors to their regular female partners in northern Thailand.

OBJECTIVE: To describe risks for HIV transmission from male blood donors to their regular female sex partners in Chiang Mai, Thailand. DESIGN: Cross-sectional study. METHODS: From March 1992 through September 1995, 405 HIV-seropositive male blood donors (index cases) and their regular female partners were enrolled in the study. Women with risk factors for HIV infection other than sexual contact with the index male were excluded. Couples were interviewed and examined; specimens were collected for laboratory analysis. RESULTS: Overall, 46% of the 405 women enrolled were HIV-positive. Ninety-eight per cent of male index cases had a history of sex with a female prostitute; 1.5% reported always using condoms with their regular partner. History of sexually transmitted disease (STD) and swollen inguinal lymph nodes in the female partner were associated with an increased risk of HIV infection in the female. History in the female of genital herpes [odds ratio (OR), 3.46; 95% confidence interval (CI), 1.50-8.78], gonorrhea or chlamydia infection (OR, 2.71; 95% CI, 1.39-5.53), and stable relationship of longer than 24 months (OR, 2.28; 95% CI, 1.02-5.09) were associated with an increased risk of HIV infection in the female. Consistent condom use in the past 2 years (OR, 0.10; 95% CI, 0.01-0.79) was associated with a decreased risk of HIV infection in the female. CONCLUSIONS: Married women in northern Thailand who appear otherwise to be at low risk for HIV infection may be exposed to this virus by their husbands. High rates of sex with commercial sex workers among men and low use of condoms within stable relationships may be important factors promoting the transmission of HIV in married couples. Programs to increase the regular use of condoms among married couples could be an important public health intervention to prevent transmission of HIV and other types of STD in northern Thailand.

PIP: The risk factors for HIV transmission from infected male blood donors to their regular female sex partners were investigated in a cross-sectional study conducted in Chiang Mai, Thailand, in 1992-95. During the 3.5-year study period, 405 couples were recruited. 98% of male blood donors reported a history of sex with female prostitutes. Only 28 men (7%) were aware of their seropositivity prior to notification by the blood bank, and just 1.5% always used condoms with their regular sex partner. 187 (46%) of the 405 female sex partners--none of whom had HIV risk factors other than sexual contact with their husbands--were HIV-positive at baseline. In the multivariate analysis, three variables were associated with a significantly increased risk of HIV in female partners: history of genital herpes (odds ratio (OR), 3.46; 95% confidence interval (CI), 1.50-8.78), history of gonorrhea or chlamydia (OR, 2.71; 95% CI, 1.39-5.53), and a stable relationship of at least 2 years' duration (OR, 2.28; 95% CI, 1.02-5.09); consistent condom use in the past 2 years was significantly associated with a decreased risk of HIV (OR, 0.10; 95% CI, 0.01-0.79). Medroxyprogesterone acetate injection and oral contraceptive use were not associated with HIV risk. These findings confirm a high risk of HIV transmission through monogamous sexual relationships in Thailand. Recommended are campaigns to increase regular condom use among married couples.

HLA gene frequencies of northern Thais.

We investigated the distribution of HLA-A and B locus, gene frequency (GF), antigen frequency (AF), haplotype frequency (HF) and non detectable antigens in Northern Thais. Of 289 native northern Thai people residing in Chiang Mai province for many generations were tested using lymphocytotoxicity test and 146 unrelated subjects were selected for analysis. The common alleles were A2, A11 and A24 for A locus with GF of 36.4%, 35.4% and 15.6%, respectively and B46, B40 and B13 for B locus with GF of 21.1%, 15.7% and 8.6%, respectively. The frequent linkage disequilibrium haplotypes were A2,B46; A33,B17 with HF of 15.9%; 5.0% and LD of 8.3%; 4.6%, respectively (p < 0.0001). The undetectable antigens (blanks) occurred with GF = 11.64% at A locus and GF = 4.92% at B locus. Comparing the GFs to other Thai ethnic groups, showed that the Northern Thais shared several alleles such as A2, A11, B46, and B62 in common with Dai Lue (Thai-speaking people who lived in the southern part of China), (p > 0.05), more than Thais, Thai/Chinese or present-day Thais (p < 0.001). Especially, HLA-B46 with the GF of 21.1% is considered to be a very typical antigen for Southern Mongoloids. These similarities will support the root of migration and origin of Northern Thais.

Infectious disease markers in blood donors in northern Thailand.

BACKGROUND: A major epidemic of human immunodeficiency virus type 1 (HIV-1) infections that are primarily due to heterosexual transmission has developed in Thailand since 1988. The epidemic has been most severe in northern Thailand. The blood banks in Chiang Mai began screening donors for HIV-1 antibodies in February 1988 and for p24 antigen in April 1992. STUDY DESIGN AND METHODS: The trends of HIV-1 antibody prevalence were analyzed by type of donor (i.e., paid, replacement, and voluntary) for the period of 1988 through 1993. In addition, the prevalence of HIV-1 p24 antigen and of antibodies to syphilis, hepatitis B surface antigen, and hepatitis C virus was evaluated among blood donors at Chiang Mai University Hospital and the Thai Red Cross blood banks in Chiang Mai. RESULTS: The prevalence of HIV-1 antibodies increased from 0.84 percent in 1988 to 4.04 percent in 1991. Seropositivity was highest in paid professional donors. After discontinuation of the use of paid donors in 1993, HIV-1 antibody prevalence decreased to 3.34 percent. Antibody prevalence in replacement donors increased from 0.56 percent in 1988 to 5.82 percent in 1991. Among 44,446 donors tested, 7 (0.016%) were HIV-1 p24 antigen positive but antibody negative. CONCLUSION: The exclusion of paid donors and the use of p24 antigen testing are justified in northern Thailand. Additional strategies to exclude donors at very high risk and to attract those at low risk for infection should be developed and evaluated to increase blood transfusion safety in this and other, similar populations.

PIP: A major epidemic of human immunodeficiency virus type 1 (HIV-1) infections has developed in Thailand since 1988. The blood banks in Chiang Mai began screening donors for HIV-1 antibodies in February 1988 and for p24 antigen in April 1992. The trends of HIV-1 antibody prevalence were analyzed by type of donor (i.e., paid, replacement, and voluntary) for the period of 1988 through 1993. In addition, the prevalence of HIV-1 p24 antigen and of antibodies to syphilis, hepatitis B surface antigen, and hepatitis C virus was evaluated among blood donors at Chiang Mai University Hospital and the Thai Red Cross blood banks in Chiang Mai. The prevalence of HIV-1 antibodies in donor sera increased from 0.84% in 1988 to 3.23% in 1989. It continued to increase in subsequent years, reaching a maximum of 4.04% in 1991; the prevalence declined slightly in 1992 and 1993. In the first year of screening, the prevalence of HIV antibodies was highest in paid professional donors. The use of paid donors was discontinued on July 1, 1992, largely because of their high rates of HIV seropositivity. This action lowered the prevalence of HIV infection in the overall donor population in 1992 to 3.61%, from the peak of 4.04% in 1991. Antibody prevalence in replacement donors increased from 0.56% in 1988 to 5.82% in 1991. Screening for p24 antigen, introduced on April 29, 1992, identified 48 infected donors (among the 44,446 donors tested in 1992 and 1993) who were HIV p24 antigen positive. Altogether, 7 (0.016%) donors tested repeatedly reactive for p24 antigen, had positive p24 antigen neutralization tests, and were negative for antibodies to HIV. The exclusion of paid donors and the use of p24 antigen testing are justified in northern Thailand. Additional strategies to exclude donors at very high risk and to attract those at low risk for infection should be developed.