Residual transfusion risk for hepatitis B and C in southern Brazil, 1991±99 E. J. Kupek Department of Public Health, Universidade Federal de Santa Catarina, Brazil Received August 2000; accepted for publication September 2000 INTRODUCTION Hepatitis B and C are most common post-transfusion infec- tions [1±3], but it was the emergence of HIV which called the attention of wider public to the need of tightening quality control of transfused blood. In Brazil, obligatory screening of blood donations for hepatitis B and C was introduced in 1993 [4], although some blood banks started screening earlier. With advancement of the HIV/AIDS epidemic, vari- ous Brazilian studies on hepatitis B and C focused on their role as co-infections for HIV-positive individuals, particularly among high-risk groups, while the data on residual trans- fusion risk remained extremely sparse. A rare exception is a study in the federal state of Sa Äo Paulo which found the risk of 1 : 3674 for hepatitis B virus (HBV) and 1 : 21231 for hepatitis C virus (HCV) being transmitted via transfused blood screened negative during an infectious window period [5]. The same study pointed out to high prevalence (23%) of HBV among blood donors in Sa Äo Paulo. HCV prevalence was estimated at 2.1% in a similar population in early nineties [6], which is higher than in most studies from North America and Northern Europe [7]. Some areas of southern Brazil are known for extremely high HBV prevalence in the general population. This may be illustrated by a recent report that almost half of blood donations in a blood bank in Chapeco  ± a town in the interior of the federal state of Santa Catarina ± were found to be HBV seropositive [8]. In the Haemotherapy Center of Santa Catarina (HEMOSC) blood bank in the state capital Floriano  polis, HBV seroprevalence in the mid-90s exceeded 5 per 1000 donors [9]. As residual transfusion risk is propor- tional to incidence and window period duration [1,2], hyperendemic areas may require a special screening strategy to minimize risk. The aim of this work is to provide ®rst estimates of residual risk of transfusing HBV and HCV con- taminated blood due to infectious window period in a high prevalence area of southern Brazil. METHODS A retrospective study of 139 188 blood donor records between 1 January 1991 and 18 June 1999 was conducted in the largest blood bank in the state of Santa Catarina, Abbreviations: anti-HBC, hepatitis B core antibody; anti-HCV, hepatitis C antibody; EIA, enzyme immunoassay; HBV, hepatitis B virus; HBsAg, hepatitis B surface antigen; HCV, hepatitis C virus; HTLV, human T-cell lymphotropic virus; STD, sexually transmitted disease; VDRL, Venereal Disease Research Laboratory. Correspondence: Professor Dr Emil Kupek, Departamento de Sau Âde Pu  blica, CCS, Universidade Federal de Santa Catarina, Campus Universita Ârio, Trindade, 88040±900 Floriano Âpolis-SC, Brazil. E-mail: kupek@repensul.ufsc.br Journal of Viral Hepatitis, 2001, 8, 78±82 Ó 2001 Blackwell Science Ltd SUMMARY. A retrospective study of 139 188 blood donor records for the period 1991±99 was conducted in the largest blood bank in the federal state of Santa Catarina, in southern Brazil. The incidence/window method, based on 11 286 repeat donors with 8917 person-years of follow-up, was used to estimate the residual risk for transfusing hepatitis B and C due to infectious window periods for early, mid and late years of the decade. The residual risk for transfusing HBsAg contaminated blood decreased almost three times over the 1990 decade but still remains very high at 1 : 2077 (95% con®dence limits 1 : 1075±1 : 4624), with a corres- ponding incidence of 3.00 (1.35±5.77) per 1000 person- years. Similarly, although residual risk for hepatitis C was reduced more than 30 times in late 1990s, compared with the earlier period, the risk of 1 : 13721 (1 : 7102± 1 : 30820) and corresponding incidence of 0.51 (0.23±0.99) per 1000 person-years are still very high compared to developed countries. In addition to vaccination against hepatitis B and health promotion efforts aimed at reduction of hepatitis transmission, special measures such as PCR screening of pooled blood donations might be needed to rapidly achieve a further residual risk reduction in high prevalence areas. Keywords: Brazil, hepatitis B, hepatitis C, residual risk, transfusion.