The prevalence of hepatitis E virus (HEV) in the Bulgarian population remains underestimated. The aim of the present study was to evaluate age and gender trends in HEV prevalence in the heterogeneous Bulgarian population. Stored serum samples from blood donors and different patient sub-populations—kidney recipients (KR), patients with Guillain–Barre syndrome (GBS), Lyme disease (LD), patients with liver involvement and a clinical diagnosis other than viral hepatitis A and E (non-AE), hemodialysis (HD) and HIV-positive patients (HIV)—were retrospectively investigated for markers of past and recent/ongoing HEV infection. The estimated overall seroprevalence of past infection was 10.6%, ranging from 5.9% to 24.5% for the sub-populations evaluated, while the seroprevalence of recent/ongoing HEV infection was 7.5%, ranging from 2.1% to 20.4%. The analysis of the individual sub-populations showed a different prevalence with respect to sex. In regard to age, the cohort effect was preserved, as a multimodal pattern was observed only for the GBS sub-population. Molecular analysis revealed HEV 3f and 3e. The type of the population is one of the main factors on which the anti-HEV prevalence depends, highlighting the need for the development of guidelines related to the detection and diagnosis of HEV infection with regard to specific patient populations.

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Hepatitis E virus (HEV) is a RNA virus that belongs to the family Hepeviridae. The virus causes self-limited acute hepatitis in immunocompetent individuals, but can become chronic or present with extrahepatic manifestations in immunosuppressed patients. In recent years, due to the increased scientific interest in HEV infection, the number of laboratory-confirmed cases have also increased. The first study of HEV infection in Bulgaria was carried out in mid-90s of the last century by Teoharov et al. Ten years later, more in-depth studies of HEV infection began. The main focus was on the evaluation of HEV seroprevalence among different target populations. Attention was also paid to the zoonotic potential of the infection. The aim of the present review is to summarize studies on HEV conducted by Bulgarian authors in regards to HEV seroprevalence among humans and animals, clinical and epidemiological characteristics of HEV infection, and molecular-characteristics of HEV.

Background: Hepatitis C virus (HCV) is an RNA virus causing acute or chronic infection and affecting more than 2% of population worldwide. The firstline tests for diagnosis of HCV infection are 3rd or 4th generation enzyme immunoassays - ELISA and CIA. They indicate the presence of antibodies against HCV in serum. These tests are characterized by high sensitivity and specificity, but they cannot distinguish past, acute or chronic infection, and sometimes produce false positive results. Confirmatory tests, such as recombinant immunoblot-line immune assay (LIA), and quantitative PCR, are used to validate the positive antibody response. The recombinant immunoblot assay can be used to determine the specificity of antibody to HCV. The aim of the present study is to determine the correlation between the anti-HCV response in confirmatory immunoblot assay and the HCV viral load, measured by PCR. Materials and methods: Twenty-nine anti-HCV positive sera were included in the study. Third generation ELISA assay was used for anti-HCV screening of the samples and for detection of anti-HCV antibodies against specific HCV proteins. Third generation line immunoassay INNO-LIA HCV Score, based on the principle of an enzyme immunoassay, was used as a confirmatory test. The HCV viral load was measured by quantitative PCR method – Abbott Real Time HCV (Abbott Molecular Inc., USA) with linear sensitivity range from 1.08 Log 10 IU/ml (12 [IU/ml]) to 8.00 Log 10 IU/ml (100 000 000 [IU/ml]). Results: HCV RNA was quantified in all studied samples. Ten of 29 serum samples (34%, Group I) were HCV RNA negative. The rest of the samples were HCV RNA positive as follows: 3 serums were with minimal viral load from < 12 to 10 000 IU/ml (10%, Group II); 3 serum samples –between 10 000 and 100 000 IU/ml (10%, Group III); 10 serum samples – between 100 000 and 1 000 000 IU/ml (34%, Group IV) and in 3 serum samples HCV RNA concentration was over 1 000 000 IU/ml (10%, Group V). Conclusion: HCV screening strategies involving anti-HCV detection by ELISA combined with recombinant immunoblot assay can be the method of choice in laboratories with limited equipment and finances.