Risk factors for HTLV-I and II in individuals attending a clinic for sexually transmitted diseases.

Background: To date, few studies have provided information on risk factors for human t-lymphotropic viruses (HTLV) types I and II in European countries. In particular, few data are available from published studies conducted in STD centers.

Goals: To identify risk factors for HTLV-I and HTLV-II infection and to better distinguish the epidemiologic patterns of the two viruses in Italy.

Study Design: A cross-sectional study of individuals at high risk of sexually or parenterally transmitted infections attending a large STD center in an urban setting was conducted. Serologic tests for HTLV-I and II, HIV, hepatitis virus type B (HBV), hepatitis virus type C (HCV), and syphilis were performed. Information regarding at-risk behavior was collected using a specific questionnaire.

Results: From January 1994 to June 1996, 1,457 individuals were recruited; of them, 1,016 (69.7%) were males, 1,051 (72.4%) Italians, and 288 (19.8%) non-Europeans. One thousand seventy-five (74.8%) participants were noninjecting-drug-using heterosexuals, 285 (19.6%) were men who have sex with men, and 97 (6.6%) were injecting drug users (IDU). The mean age of the study participants was 33.6 (+/-10.5) years. Nine (0.6%) individuals were positive for HTLV-I antibodies and 9 (0.6%) for HTLV-II antibodies. The prevalence of HTLV-I among IDUs, men who have sex with men, and noninjecting-drug-using heterosexuals, was 2.1% (2/97), 1.4% (4/ 285), and 0.3% (3/1085), respectively. HTLV-II prevalence was 8.2% (8/97) among IDUs and 0.09% (1/1075) among noninjecting-drug-using heterosexuals. Among the nine HTLV-II-positive individuals, eight were Italian IDUs and one was a noninjecting-drug-using heterosexual man from India. None of the 285 men who have sex with men had HTLV-II antibodies. HTLV-infected individuals tended to be older than those who were uninfected. HTLV-I-infected individuals were more likely to be non-European and to have antibodies against Treponema pallidum. Injecting drug use tended to be independently associated with HTLV-II infection.

Conclusions: The data suggest a role of sexual behavior in the spread of HTLV-I, which is more likely to be detected in individuals coming from endemic areas. Injecting drug use remains the most important risk factor for HTLV-II infection in Italy.