Circulation of West Nile virus and Usutu virus in birds in Germany, 2021 and 2022.

Background: Usutu virus (USUV) and West Nile virus (WNV) are zoonotic arthropod-borne orthoflaviviruses. The enzootic transmission cycles of both include mosquitoes as vectors and birds as amplifying hosts. For more than 10 years, these viruses have been monitored in birds in Germany by a multidisciplinary network.