en Infectious Diseases Infectious Diseases پژوهشي Original Article <p style="margin: 0px; text-align: justify; line-height: 200%;"></p> <p style="margin: 0px; text-align: justify; line-height: 200%;">Background: Human T-cell lymphotropic viruses 1 (HTLV1) is endemic in specific regions. We aimed to determine the prevalence of HTLV I infection among blood donors in southeast Iran.&nbsp;&nbsp;<br> Methods: This cross-sectional study was conducted between April 2005 and March 2015. Sera were collected from blood donors and were tested for the presence of HTLV1 specific antibody using ELISA. Reactive samples were then tested by Western blot for confirmation.<br> Results: Of the 165,267 blood donors tested for HTLV 1 antibody, 45 (0.027%) donors were positive. Out of 45 positive donors, 41 were first time blood donors, 3 were repeat blood donors and 1 as regular donor. Most HTLV-1-positive donors were male and married. Co-infection with HBV was observed in one subject. The percentage of positive samples had increasing patterns from 0.016% in 2009 to 0.084% in 2010 and decreased after that to 0.014% in 2015.<br> Conclusion: The results indicated a low level of infection of HTLV1 in this part of our country.&nbsp;</p> HTLV infection, Blood donors, Prevalence, Seropositivity 47 50 http://ijbc.ir/browse.php?a_code=A-10-301-3&slc_lang=en&sid=1 Shirin Ferdowsi fedowsishirin@gmail.com 10031947532846004861 10031947532846004861 No 1. Blood Transfusion Research Center, High Institute for Research and Education in Transfusion Medicine, Mahsa Najafzadeh 10031947532846004862 10031947532846004862 No Birjand University of medical sciences, Birjand, Iran Mohammad Reza Ameli 10031947532846004863 10031947532846004863 No Blood Transfusion Research Center, South Khorasan Regional Transfusion Center, Birjand, Iran Seyed Mehdi Sajjadi ferdowsishirin@gmail.com 10031947532846004864 10031947532846004864 Yes Cellular and molecular research center, Birjand university o medical sciences