BACKGROUND: Tick-borne encephalitis (TBE) is an important cause of viral infections of the central nervous system (CNS). A rising incidence of TBE in Europe in recent years emphasizes the need for continued awareness of this vaccine-preventable disease, however the disease spectrum of TBE infections in adults and children is not well described. We aim to systematically analyze recent study evidence on symptomatic TBE infections.
METHODS: We conducted a systematic literature review of primary data studies published since 2007 on individuals with TBE infection (limited to cases with CNS manifestations). We included papers with >20 subjects and representative study populations from European countries. After removing duplicate datasets, papers were assessed for quality, abstracted and analyzed using descriptive statistics.
RESULTS: We identified 1,632 publications, with 15 reporting laboratory-confirmed TBE infections in unique hospitalized populations: 5,701 in adult subjects; 678 in children. Overall, paediatric cases were most likely to have a meningitic presentation of TBE (weighted average proportions: meningitis= 76.9% [range 57.5-95.7%], encephalitis= 22.7% [2.9-41.4%], myelitis= 0.4% [0-1.4%]), and adults a meningitic or encephalitic presentation (32.6% [9.8-57.7%], 61.0% [27.9-86.6%], 5.9% [0-11.3%] respectively). Similar weighted average proportions of adults and children were admitted to ICU (adults: 15.5%, children 16.4%) and died (adults: 0.9%, children 0%). Outliers were present for many datapoints.
DISCUSSION: Sufficient robust data were available to describe the clinical spectrum of TBE in hospitalized adults and children. Our data suggests that meningitic presentations are most common in children and meningitic or encephalitic presentations in adults, resulting in similar outcomes. The evidence is challenging to aggregate due to heterogeneity, in the categorization of CNS manifestations, the denominator populations, and due to differences in healthcare systems and diagnostic practices across countries. Further work is needed on outcome data by manifestation, non-European subtypes of TBE, and TBE virus manifestations that do not include CNS symptoms.
