During a 2-year period, blood samples from 2505 Lebanese blood donors were chosen at random, at various periods of time at one blood donation centre (Hotel Dieu de France, Beirut, Lebanon) and were screened for markers of HBV infection (HBsAg, anti-HBc and anti-HBs). The study showed HBsAg positivity of 0.6% and an overall exposure rate to HBV of 10.0%. Out of the 2505 blood donors screened, 56 (22%) were found to be 'anti-HBc alone' positive which is almost four times the HBsAg positivity. The 56 'anti-HBc alone' samples were retested by another ELISA kit commercially available and 54 samples were 'anti-HBc alone' positive by both assays. The 54 samples had no serological markers as evidence of infection with human immunodeficiency virus (HIV) or hepatitis C virus (HCV). Only seven (13%) out of the 54 samples were HBV DNA positive by PCR and all were HBV genotype D. All seven HBV DNA-positive samples had HBV DNA levels below 400 copies/ml. Although any circulating HBV DNA among our 'anti-HBc alone' blood donors was below the detection limit of our Amplicor Monitor assay, some of these samples had circulating virus. A national study, where a larger number of blood donors from different blood donation centres across the country will perhaps determine whether screening for anti-HBc in addition to HBsAg detection is needed in Lebanese blood donors.

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Recently we identified hepatitis C virus (HCV) genotype 4 as the principle genotype among Lebanese thalassaemics. In an attempt to confirm the predominance of genotype 4 in Lebanon and perhaps in the Middle East, genotyping was attempted on 142 HCV-infected Lebanese patients from five different hospitals in the country. These included 38 HCV-positive patients with symptomatic liver disease who were referred to gastroenterologists and 104 HCV-positive patients with no symptoms of liver disease: 27 patients with thalassaemia, 30 patients on haemodialysis, 32 multi-transfused and 15 intravenous drug users. HCV genotyping was performed on PCR HCV RNA-positive samples using a commercial line probe assay (LiPA; Innogenetics, Ghent, Belgium). HCV genotype 4 is found to be the predominant genotype among HCV-infected Lebanese patients (ranging from 34.2% to 53.3%) followed by 1a (ranging from 12.5% to 43.3%) and 1b (ranging from 8.0% to 34.4%). In patients with symptomatic liver disease, however, genotype 4 (34.2%) was preceded by genotype 1a (39.5%). The predominance of HCV genotype 4 in our population (45.7%) confirms the predominance of HCV genotype 4 in Lebanon and most of the Arab countries in the Middle East but contrasts with data reported from non-Arab Middle Eastern Countries as can be seen from the literature review. Implications of genotyping for clinical outcome of HCV infection, response to treatment as well as for vaccine development are discussed.

Recently the prevalence of hepatitis B virus (HBV) genotypes and the association between these genotypes and the clinical status of HBV-infected patients were recently investigated in the Lebanese population. The aim of the additional study reported here was to determine the current prevalence of hepatitis delta virus (HDV) infection and the range of HDV genotypes in this Lebanese population. Two hundred and fifty-eight HBsAg-positive patients (107 asymptomatic blood donors, 92 with chronic hepatitis, 24 with cirrhosis, 15 with hepatocellular carcinoma, 20 patients on haemodialysis) from ten medical centers in Lebanon were tested for antibody to hepatitis D virus (anti-HDV). Those testing positive were analysed further for HDV-RNA and for genotyping by reverse transcriptase-polymerase chain reaction (RT-PCR) and restriction fragment length polymorphism (RFLP). Three samples (1.2%) were anti-HDV positive and out of these, only one was HDV-RNA positive (0.6%) and was analysed as HDV genotype I. Our results point to a low endemicity of HDV in the Lebanese population which is in sharp contrast to data reported from Lebanon 20 years ago and to the situation in neighbouring Arab and non-Arab countries in the Mediterranean region. HDV genotype I seems to be the predominant genotype in Lebanon and the Middle East.

Occult hepatitis B virus (HBV) infection, characterised by the presence of HBV infection with undetectable hepatitis B surface antigen (HBsAg), was investigated in 98 Lebanese patients with chronic hepatitis C liver disease and 85 control subjects recruited from eight institutions in different parts of the country. The prevalence of occult HBV infection ranged from 11.9% to 44.4% in hepatitis C virus (HCV)-infected patients and it increased with increasing severity of the liver disease. The overall rate of HBV DNA in our 98 HCV-infected patients was 16.3%. On the other hand, the rate of HBV DNA was 41.0% in anti-HBc alone positive patients compared to only 7.1% in healthy controls who were also anti-HBc alone positive (p < 0.001). Moreover, the prevalence HBV DNA increased with increasing severity of the liver disease, but this increase was only marginally significant and, perhaps, could have been significant if more patients were involved in the study. Although Lebanon is an area of low endemicity for both HBV and HCV, occult HBV infection is common in HCV-infected patients. The presence of HBV DNA, therefore, presents a challenge for the effective laboratory diagnosis of hepatitis B, particularly if polymerase chain reaction (PCR)-based HBV detection methods are not used.