Seroprevalence of West Nile virus, Greece, 2020

BackgroundWest Nile virus (WNV) is a growing public health concern in Europe. Greece is one of the most affected countries in Europe, with the highest annual incidences.AimWe aimed at assessing IgG antibodies to WNV in the Greek population and compared the results with a nationwide survey conducted in the period 2012-2013.MethodsIn a geographically stratified sampling, 4,416 serum samples were collected and analysed for WNV-specific IgG antibodies using ELISA. Samples positive for WNV IgG were further tested with a WNV serum neutralisation test to detect false positives.ResultsThe weighted seroprevalence, adjusted for age, sex and region, was 2.83% (95% confidence interval (CI): 2.32-3.44) in the 4,416 samples tested, significantly higher than in the 2012-2013 survey (1.55%; 95% CI: 1.17-2.04). The seropositivity increased with age with the highest seroprevalence in persons aged ≥ 80 years (6.04%; 95% CI: 3.28-10.88). No significant differences in seropositivity were observed between sexes or regions. We estimated that 312 (95% CI: 256-379) persons had a WNV infection per a case of West Nile neuroinvasive disease (WNND). A certain degree of discordance was observed between areas with increased seroprevalence and those with an increased incidence of WNND.ConclusionOur study reveals a wider geographical spread of WNV infections in Greece compared with previous investigations. The nearly twofold increase in seroprevalence highlights the need for ongoing monitoring and preventive measures to mitigate the impact of WNV on public health in Greece.