Unprecedented increase of West Nile virus neuroinvasive disease, Spain, summer 2020

Cases of West Nile neuroinvasive disease (WNND) in Spain increased in summer 2020. Here we report on this increase and the local, regional and national public health measures taken in response. We analysed data from regional surveillance networks and the National Epidemiological Surveillance Network, both for human and animal West Nile virus (WNV) infection. During the 2020 season, a total of 77 human cases of WNV infection (median age 65 years; 60% males) were detected in the south-west of Spain; 72 (94%) of these cases developed WNND, presenting as meningoencephalitis, seven of which were fatal. In the previous two decades, only six human cases of WNND were detected in Spain. Reduced activities for vector control this season, together with other factors, might have contributed to the massive increase. Public health measures including vector control, campaigns to raise awareness among physicians and the general population, and interventions to ensure the safety of donations of blood products, organs, cells and tissues were effective to reduce transmission. Going forward, maintenance of vector control activities and an update of the vector-borne diseases response plan in Spain is needed.