Research Article: HTLV-1 is predominantly sexually transmitted in Salvador, the city with the highest HTLV-1 prevalence in Brazil

Date Published: February 3, 2017

Publisher: Public Library of Science

Author(s): David Nunes, Ney Boa-Sorte, Maria Fernanda Rios Grassi, Graham P. Taylor, Maria Gloria Teixeira, Mauricio L. Barreto, Inês Dourado, Bernardo Galvão-Castro, William M. Switzer.


Salvador is the city with the highest number of HTLV-1 infected individuals in Brazil, yet the main route of HTLV-1 transmission is unknown.

To investigate the association of syphilis infection as a proxy for sexual transmission of HTLV-1 infection in the general population of this city.

A cross sectional population-based study was conducted with 3,451 serum samples obtained by a representative simple random sampling. Data on gender, age, income, and years of education were collected by questionnaire and the presence of HTLV, HIV and Treponema pallidum infection was determined by serology. Logistic regression analysis was used to evaluate the independent effect of the potential explanatory variables to HTLV-1 infection and Odds Ratios (OR) and 95% CI were calculated.

The majority of studied individuals were female (56.4%), had less than 7 years of education (55.3%) and earned two or less minimum wages (52.0%). The overall prevalence of HTLV-1 was 1.48% (51/3,451; 95% CI: 1.10%– 1.94%), which increased with age. Only three persons younger than 17 (3/958; 0.31%; CI 95% 0.06–0.91) years were infected by HTLV-1. Among the 45 syphilis positives, 12 (26.7%) were HTLV positive, while among 21 HIV positives, only one (4.8%) was HTLV positive. HTLV-1 infection was found to be associated with syphilis infection (ORADJUSTED 36.77; 95% CI 14.96–90.41).

The data presented herein indicate that horizontal transmission between adults is the main route of HTLV-1 infection in the general population of Salvador and that this is likely to occur through sexual contact.

Partial Text

Human T lymphotropic virus type-1 (HTLV-1) is a delta retrovirus of worldwide distribution and it is estimated that at least 5–10 million people harbor the virus [1]. To identify the risk of transmission via tissue transplantation, high prevalence has been defined as greater than 1% in the general population or greater than 1 in 10,000 first time blood donors[2]. The highest areas of prevalence are located in Japan, Africa, the Caribbean Islands, Melanesia, the Mashhad area of northeastern Iran and South America. Brazil, which potentially harbors 800,000 people with HTLV-1, represents the largest number of carriers on the American continent [1, 3].

The study population comprised 3,451 subjects of which 1,947 (56.4%) were females; age ranged from 0 to 99 years. Eleven (0.32%) and 23 (0.67%) subjects provided no information about sex and age, respectively. The majority (55.3%; 1895/3425) had less than seven years of education and 52.0% (1660/3192) earned two MW or less.

The city of Salvador continues to be an important location for HTLV-1 infection surveillance, as the prevalence among the general population remains above 1% (1.45%). In addition, very few studies involving large samples have investigated HTLV among the general population [24].




0 0 vote
Article Rating
Notify of
Inline Feedbacks
View all comments