Emergence of Usutu virus in Hungary

Tamás Bakonyi^*, Károly Erdélyi, Krisztina Ursu, Emke Ferenczi, Tibor Csörg, Helga Lussy, Sonja Chvala, Christiane Bukovsky, Tanja Meister, Herbert Weissenböck, and Norbert Nowotny

Department of Microbiology and Infectious Diseases, Faculty of Veterinary Science, Szent István University, Hungária krt. 23-25, H-1143 Budapest, Hungary; Zoonoses and Emerging Infections Group, Clinical Virology, Clinical Department of Diagnostic Imaging, Infectious Diseases and Clinical Pathology, University of Veterinary Medicine, Vienna, Veterinaerplatz 1, A-1210 Vienna, Austria; Central Veterinary Institute, Tábornok u. 2, H-1147 Budapest, Hungary; National Center for Epidemiology, Gyáli u. 2-6, H-1097 Budapest, Hungary; Department of Anatomy and Cell Biology, Faculty of Science, Eötvös Loránd University, Pázmány Péter sétány 1/A, Budapest, H-1117 Hungary; Department of Pathobiology, Institute of Pathology and Forensic Veterinary Medicine, University of Veterinary Medicine, Vienna, Veterinaerplatz 1, A-1210 Vienna, Austria

^* To whom correspondence should be addressed. Email: Bakonyi.Tamas{at}aotk.szie.hu.

	Abstract

In 2001, Usutu virus (USUV), a mosquito-borne flavivirus of the Japanese encephalitis virus serogroup, related to West Nile virus and previously restricted to sub-Saharan Africa, emerged in wild and zoo birds in and around Vienna, Austria. In order to monitor the spread of the infection, a dead-bird surveillance program was established in Austria and in neighboring Hungary. In Hungary, 332 dead birds belonging to 52 species were tested for USUV infection between 2003 and 2006. In the first two years, all investigated birds were negative. In August 2005, however, USUV was detected in organ samples of a blackbird (Turdus merula), which was found dead in Budapest, by RT-PCR, immunohistochemistry and in-situ hybridization. In July and August 2006, further six dead blackbirds tested positive for USUV, and the virus was isolated from organ samples of one bird. These birds were also found in urban areas of Budapest. The nearly complete genomic sequence of one Hungarian USUV strain was determined; it shares 99.9% identity with the strain circulating in Austria since 2001. This result indicates that the USUV strain responsible for blackbird die-off in Budapest most likely spread from Austria to Hungary, rather than it was independently introduced from Africa.