Prevalence of human T-lymphotropic virus type 1 and 2 infection in Sweden

Background: Prevalence data on human T-lymphotropic virus types 1 and 2 (HTLV-1/2) in Sweden have not been updated since 1995. The seroprevalence among blood donors at that time was 0.2/10,000. A few years earlier, a high prevalence of HTLV-2 was found in intravenous drug users (IDUs) in Stockholm (3.4%). The objective of this study was to update information on the seroprevalence of HTLV in several study groups. Methods: Serum samples from pregnant women, hepatitis C virus (HCV)-positive individuals, and IDUs in Stockholm were investigated for HTLV-1/2 antibodies. Data from the mandatory HTLV-1/2 screening (2003-2006) of in vitro fertilization (IVF) clients were compiled, as well as data from new blood donors. Results: Eight out of 35,000 IVF patients were positive for anti-HTLV-1/2 (seroprevalence 2.3 per 10,000). Of the anti-HCV-positive individuals (n = 355), 1 sample was HTLV-1-positive (28.2 per 10,000). From 1995 to 2007, 18 HTLV-positive new blood donors were identified out of approximately 550,000 individuals tested (0.3 per 10,000). Thirty-five of 1079 tested IDUs were screening reactive. Conclusions: Since the start of screening in 1994, there has been no increased seroprevalence of HTLV-1/2 among blood donors in Sweden. Seroprevalence among Swedish IVF patients is 10 times higher than among blood donors. This finding is comparable to a 2003 European seroprevalence study of pregnant women in 7 countries. However, the possibility that the IVF group includes individuals with a higher risk of acquiring sexually transmitted infections, including HTLV, than the general population cannot be ruled out.