Tick-borne encephalitis (TBE) virus is a major cause of central nervous system infections in endemic countries. Here, we present clinical and laboratory characteristics of a large international cohort of patients with confirmed TBE using a uniform clinical protocol. Patients were recruited in eight centers from six European countries between 2010 and 2017. A detailed description of clinical signs and symptoms was recorded. The obtained information enabled a reliable classification in 553 of 555 patients: 207 (37.3%) had meningitis, 273 (49.2%) meningoencephalitis, 15 (2.7%) meningomyelitis, and 58 (10.5%) meningoencephalomyelitis; 41 (7.4%) patients had a peripheral paresis of extremities, 13 (2.3%) a central paresis of extremities, and 25 (4.5%) had single or multiple cranial nerve palsies. Five (0.9%) patients died during acute illness. Outcome at discharge was recorded in 298 patients. Of 176 (59.1%) patients with incomplete recovery, 80 (27%) displayed persisting symptoms or signs without recovery expectation. This study provides further evidence that TBE is a severe disease with a large proportion of patients with incomplete recovery. We suggest monitoring TBE in endemic European countries using a uniform protocol to record the full clinical spectrum of the disease.

The current low coverage of vaccination leads to an insignificant improvement to the overall frequency of this disease.

Between 1960-2005, 1,621 cases of tick-borne encephalitis were confirmed by laboratory testing in the region of West Bohemia (now the regions of Pilsen and Karlovy Vary) which represents a rate of infection of 4.1 per 100,000 inhabitants per year. The highest infection rate was established in men aged 20-24 and women aged 45-54. Over the monitored years, there was a significant shift of the maximum infection rate into an older age group. Currently, it is the 45-64 age group which carries the highest rate of infection. Of the identified disease cases, 12 were lethal, which represents 0.7% of the total. Over the years, the risks of transmission in particular areas of the region have changed. The highest infection rate is currently in the district of Klatovy (21.7 per 100,000 inhabitants per year). Of the total number, only two cases were contracted outside the Czech Republic (Slovakia and Austria). In 4.8% cases, the patient's anamnesis showed data on the consumption of non-pasteurized milk. 3.0% of infections probably originated as a result of professional exposure. Over the years, the season of infection has extended. Presently, the transmission can occur anytime between March and November. According to official data, only 6.7% of the population in the Pilsen district has been vaccinated so far. The low percentage of vaccinated cases may, however, in no way influence the unfavorable epidemiological situation regarding tick-borne encephalitis.

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