West Nile Virus (WNV) was first detected in 1937 in the West Nile district of Uganda. In Europe, it first appeared in France in the early 1960s. So far, infections in humans, horses and birds have been reported especially from southern and southeastern European countries. WNV occurs on all continents. It first appeared in the USA in 1999 and spread within a short time throughout the country and as far as Canada.
In Germany, the first infected bird, a bearded owl from aviary husbandry in Halle a. d. Saale, was found at the end of August 2018. By the end of the year there were a total of 12 cases in birds and two cases in horses. For 2019, the National Reference Laboratory for West Nile Virus infections already detected the first official case at the beginning of July, followed by more than 70 cases by the end of the year. It can therefore be assumed that WNV has been able to successfully winter in native mosquitoes in Germany. In autumn 2019, the virus was also detected for the first time in mosquitoes of the Culex pipiens complex, known as vectors, in Germany. In 2020, the first case of WNV occurred in the middle of July. Until the end of the year, a total of 63 WNV detections were identified in zoo and wild birds and 22 infected horses were detected, all with more or less severe clinical signs. The majority of cases in birds and horses were confirmed in the already known affected regions of Eastern Germany (federal states of SN, ST, BB, BE). For the first time in the federal state of Thuringia, WNV infection was also detected in diseased and/or dead zoo and wild birds, and a tendency to spread to other districts of Brandenburg was observed. Furthermore, the spread to the federal state of Lower Saxony, district of Helmstedt (one horse with neurological symptoms), was detected. This demonstrated a spreading tendency of WNV compared to 2019. Also in 2020, WNV was detected in mosquito populations in affected areas and a significant increase in human cases of disease was recorded.
Blood-sucking mosquitoes transmit the virus. The main hosts are birds. In rare cases, transmission to horses and humans can also occur. Therefore the FLI has been observing the spread of WNV in Europe for years.