Denmark: Usutu virus detected in blackbirds, First such cases in the country
According to Danish health officials, for the first time, Usutu virus (USUV) has been detected in birds in Denmark.
Three birds have been found positive for USUV, and these are two adult blackbirds and one young bird. The birds have been found respectively in Southern Jutland (Aabenraa), Zealand (Hundested) and Bogø.
The birds have been collected via Fall Game Monitoring and have been analyzed by the Danish Veterinary Consortium, a collaboration between the Statens Serum Institut and the University of Copenhagen. Similar unusual symptoms have been observed in blackbirds in several other places in the country over the summer, and in many cases the sick birds have been young birds, i.e. blackbird chicks hatched in Denmark this year. It is likely that the birds have been infected in this country.
USUV is an emerging arbovirus that was first isolated in South Africa in 1959. This Flavivirus is maintained in the environment through a typical enzootic cycle involving mosquitoes and birds.
USUV has spread to a large part of the European continent over the two decades mainly leading to substantial avian mortalities with a significant recrudescence of bird infections recorded throughout Europe within the few last years.
In recent years, USUV has spread from Africa to Europe, first to countries in Southern and Central Europe and then to Northern Europe. During the first recorded outbreaks in Germany in 2011-2012, the authorities estimated that approx. 200,000-400,000 blackheads died. In 2019, the virus was detected in a single blackbird on Öland in Sweden.
USUV infection in humans is considered to be most often asymptomatic or to cause mild clinical signs. Nonetheless, a few cases of neurological complications such as encephalitis or meningoencephalitis have been reported.