A case-control study of risk factors associated with human T-cell lymphotrophic virus type-I seropositivity in blood donors from Guadeloupe, French West Indies

Background and objectives: An age- and gender-specific distribution characterizes human T-cell lymphotrophic virus type-I (HTLV-I) seropositivity in Guadeloupe (French West Indies). Further epidemiological studies are required to identify other possible risk factors associated with this retroviral infection. Materials and methods: A nested case-control study was conducted between 1997 and 1999 among blood donors. A total of 102 HTLV-I-positive subjects were matched (at a ratio of 1: 3) by gender, age (±5 years) and donor status (new or regular) to 306 HTLV-I-negative controls. Information was obtained through a questionnaire assessing both environmental and behavioural variables. Results: Factors independently associated with HTLV-I infection included a low level of education [odds ratio (OR) 6·61, confidence interval (CI) 2·89-15·15], black ethnicity (OR 3·28, CI 1·01-10·65), two or more sex partners in the previous 3 years (OR 2·43, CI 1·16-5·10), early age at first sexual intercourse (0·84 risk reduction per additional year, CI 0·76-0·93), a history of sexually transmitted diseases (OR 2·29, CI 1·0-5·34) and positive Chlamydia serology (OR 1·95, CI 1·03-3·68). Conclusion: These data provide a wide spectrum of features associated with HTLV-I seropositivity, especially sexual risk factors. It strongly suggests that heterosexual intercourse is an important route of HTLV-I transmission in Guadeloupe, even among low-risk populations such as blood donors.