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In biphasic tick-borne encephalitis (TBE), the virus can be detected by polymerase chain reaction (PCR) in blood during the viremic phase of illness. This latter high rate, however, might be due to the lack of detection and reporting of mild cases (Charrel et al., 2004 Gritsun et al., 2003 Kaiser, 1999 Lindquist, 2014). For infections with the Siberian and Far Eastern subtypes, mortality ranges between 2 and 3 % and about 35 %, respectively. Case fatality rates range between 0 and 1.4 % and increase with age for European subtype viruses. Chronical forms may be observed in association with the Siberian subtype (Gritsun et al., 2003). In contrast, Far Eastern and Siberian viruses most often induce monophasic diseases. Symptomatic disease is typically biphasic when caused by European subtype viruses, including a viremic stage with flu-like symptoms starting about 8 days (4–28 days) after the tick bite, an asymptomatic interval of about one week (range 1–33 days), and a second stage with neurological manifestations ranging from mild meningitis to severe encephalitis with or without myelitis and spinal paralysis (Lindquist, 2014 Lindquist and Vapalahti, 2008). Infections with TBEV are asymptomatic in 70–95% of cases. In Central Europe, TBEV is principally transmitted by Ixodes ricinus (Lindquist, 2014), although its presence in other tick species as well as the transmission via infected milk products has also been documented (Balogh et al., 2010 Holzmann et al., 2009 Mierzejewska et al., 2015). TBEV is typically transmitted through bites of infected ticks, wherefore its distribution correlates with the presence of ixodid vectors. These subtypes correspond to the major TBEV genotypes 1, 2, and 3, respectively (Demina et al., 2010 Lindquist, 2014). Based on antigenetic properties, it is subdivided into a Far Eastern, a European and a Siberian subtype. The TBEV species belongs to the mammalian tick-borne flavivirus group in the genus Flavivirus, family Flaviviridae. Tick-borne encephalitis virus (TBEV) is the most important tick-borne arbovirus infecting humans in Europe and Asia. In routine diagnostics, specificity problems are of major relevance and may be addressed by analyzing the respective samples using SNT. In relation to these values, false-positive results were observed mainly for Euroimmun Vienna IgG and RIDASCREEN IgG, whereas false-negative results were primarily observed for Virion\Serion IgG and RIDASCREEN IgM kits. Reference values defined by serum neutralization test (SNT, n = 25) or results provided by EQA organizers (n = 2) were established for a subset of samples. In total, discrepant test results for IgG and/or IgM were observed for 37/251 (14.7 %) of tested samples differences were statistically significant. Here, we evaluated three commercially available anti-TBEV IgG and IgM ELISAs using 251 serum samples: the SERION ELISA classic FSME Virus/TBE Virus IgG and IgM kit (Virion\Serion), the RIDASCREEN ® FSME/TBE IgG and IgM kit (R-Biopharm), and the anti-FSME/TBE virus ELISA “Vienna” IgG/anti-FSME/TBE virus ELISA IgM kit (Euroimmun). For reasons of simplicity, automatization and quick availability of test results, enzyme-linked immunosorbent assays (ELISAs) are the method of choice for serological diagnosis of TBE. The diagnosis of this disease is essentially based on the demonstration of specific antibodies. Tick-borne encephalitis (TBE) is endemic in many parts of Europe and Asia.
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