Re-emergence of severe West Nile virus neuroinvasive disease in humans in Romania, 2012 to 2017-implications for travel medicine

Background: In Romania, after a major outbreak in 1996, West Nile neuroinvasive disease (WNND) was reported only in a limited number of cases annually. During 2016-2017, a significant increase in the number of WNND cases was reported at the national level, associated with high mortality rates. Methods: A retrospective analysis of all cases confirmed with WNND, hospitalized during 2012-2017 in a single tertiary facility from Bucharest was performed in order to determine the annual prevalence and mortality rate and the risk factors associated with a severe outcome. Results: 47 cases were confirmed as WNND. The mortality rate was 25.5%, all death occurred during 2016-2017. Coma, confusion, obtundation, sleepiness and depressed deep tendon reflexes were symptoms predicting a severe outcome. In a univariate analysis age (p < 0.001), associated cancers (p = 0.012) and low levels of chloride in the CSF (p = 0.008) were risk factors for mortality. In a multinomial logistic analysis, age older than 75 years remained the only independent predictor of death in WNND. Conclusions: The increase in both the number and the mortality rate of WNND cases suggest a changing pattern of WNV infection in Romania. Public health authorities and clinicians should be aware of the risk of severe WNV infection in travelers returning from Romania.