Mailles et al.
Changing profile of encephalitis: results of a 4-year study in France
Infect Di. Now. 2021; S2666-9919(21)00545-5. doi: 1016/j.idnow.2021.11007.

Since the last nationwide prospective cohort study in 2007, to assess the epidemiology of acute encephalitis in France, various infectious diseases responsible for neurological presentations emerged in France, like Zika and TBE. Therefore, a reassessment of epidemiology has been conducted by a new prospective cohort study from 2016 to 2019 among patients aged at least 18 years, hospitalized in 62 clinics across France.

A total of 494 patients aged between 18 to 94 years were enrolled, of which 466 (95%) were autonomous in daily routine activities, and 57 patients were categorized as immunocompromised. The median duration of hospitalization was 21 days and 205 patients required intensive care unit admission. The overall fatality rate was 8%.

A causative agent was identified in 324/497 (65.7%) of cases. Among them, viruses represented 81.8% of known causes. Herpesviridae were the most frequently involved viruses (n=206, 63.6%), while 35 (10.8%) were related to arboviruses. A total of 26 patients (8% of cases with an identified cause) suffered from TBE.

TBE became the third cause of infectious encephalitis, just after HSV and VZV. These major changes reinforce the need for surveillance and investigation of clusters of arbovirus cases and emphasize the need for regular studies to monitor the evolution of infectious encephalitis.

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