BRIEF REPORT: EPIDEMIOLOGY AND SOCIAL SCIENCE HTLV- I in the General Population of Salvador, Brazil A City With African Ethnic and Sociodemographic Characteristics

The city of Salvador has the highest prevalence of HTLV-I among blood donors in Brazil. To study the prevalence of HTLV-I among the general population of Salvador, 30 “sentinel surveillance areas” were selected for the investigation of various infectious diseases, and 1385 individuals within these areas were surveyed according to a simple random sample procedure. ELISA was used to screen plasma samples for antibodies to HTLV-I, and the positive samples were tested by a confirmatory assay (Western blotting). The overall prevalence of HTLV-I was 1.76% (23/1385). Infection rates were 1.2% for males and 2.0% for females. Specific prevalence demonstrated an increasing linear trend with age. No one younger than 13 years of age was infected. Multivariate analysis estimated adjusted odds ratios for the association of HTLV-I with age of 9.7 (3.3; 30.4) for females and 12.3 (1.47; 103.1) for males. Less education and income might be associated with HTLV-I infection in females. Phylogenetic analysis of the long terminal repeat fragments showed that most of the samples belonged to the Latin American cluster of the Transcontinental subgroup (Cosmopolitan subtype). For the entire city of Salvador, it is estimated that ∼40,000 individuals are infected with HTLV-I. Our results suggest multiple post-Colombian introductions of African HTLV-Ia strains in Salvador. (J Acquir Immune Defic Syndr 2003;34:527–531) HTLV-I and HTLV-II were identified in 1980 and 1982, respectively. Transmission occurs through sexual contact, blood transfusion, and sharing of injecting equipment as well as vertically (mother to child) via breast-feeding. HTLV-I infection is endemic in Japan, Melanesia, Central and West Africa, and South America. So far, 6 genetic subtypes have been proposed in the phylogenetic classification of this virus: Ia, Cosmopolitan (worldwide distribution); Ib, Central African; Ic, Melanesian (a divergent strain isolated in Papua New Guinea and Australia); Id, isolated from Central African Republic pygmies and 2 patients from Cameroon and Gabon; Ie and If, recently proposed as new subtypes (identified in 1 Efe pygmy from the Democratic Republic of Congo and 1 individual from Gabon). The Cosmopolitan subtype contains five subgroups that are based on geographic distribution: Transcontinental (A), Japanese (B), North African (C), West African (D), and Black Peruvian. In Brazil, a nationwide survey of blood donors from 5 state capitals in 1993 demonstrated a mean HTLV-I prevalence of 0.45%; the highest rate (1.35%) was found in Salvador. In this city, previous studies of some specific populations, including intravenous drug users, demonstrated HTLVI, HTLV-II, and HIV-1 prevalences of 22%, 11.3%, and 44.1%, respectively. Of 6754 pregnant women, 53 (0.78%) were seropositive for HTLV-I, and 2 (0.03%) were seropositive for HTLV-II. In addition, both HTLV-I–associated myelopathy/tropical spastic paraparesis and adult T-cell leukemia/lymphoma have been described in Salvador. Salvador is the capital of Bahia State in northeast Brazil and presents wide socioeconomic differences. The population of ∼2.5 million inhabitants is roughly 80% black or racially mixed African and Portuguese descendents. So far, HTLV-I prevalence studies in Brazil have examined specific groups such as blood donors, intravenous drug users, and patients with HTLV-I–associated myelopathy/tropical spastic paraparesis or adult T-cell leukemia/lymphoma. All HTLV-I isolates studied in this country have been found to belong to the Cosmopolitan subtype. Although a few isolates cluster inside the Japanese subgroup, most belong to the Transcontinental subgroup. We report epidemiologic and molecular data for a sample of the general population in Salvador.