A One Health view of the West Nile virus outbreak in Andalusia (Spain) in 2020.

Reports of West Nile virus (WNV) associated disease in humans were scarce in Spain until summer 2020, when 77 cases were reported, eight fatal. Most cases occurred next to the Guadalquivir River in the Sevillian villages of Puebla del Río and Coria del Río. Detection of WNV disease in humans was preceded by a large increase in the abundance of in the neighbourhood of the villages where most human cases occurred. The first WNV infected mosquitoes were captured approximately one month before the detection of the first human cases. Overall, 33 positive pools of and one pool of were found. Serology of wild birds confirmed WNV circulation inside the affected villages, that transmission to humans also occurred in urban settings and suggests that virus circulation was geographically more widespread than disease cases in humans or horses may indicate. A high prevalence of antibodies was detected in blackbirds () suggesting that this species played an important role in the amplification of WNV in urban areas. was the main vector of WNV among birds in natural and agricultural areas, while its role in urban areas needs to be investigated in more detail. may have played some role as bridge vector of WNV between birds and humans once the enzootic transmission cycle driven by occurred inside the villages. Surveillance of virus in mosquitoes has the potential to detect WNV well in advance of the first human cases.