Usutu virus, Austria and Hungary, 2010-2016.

Area of Science:

• Veterinary Virology
• Epidemiology of Emerging Infectious Diseases
• Avian Pathology

Background:

• Usutu virus (USUV) first emerged in Europe in 2001, causing significant wild bird mortality, particularly in blackbirds.
• Following its initial detection, USUV spread to several European countries between 2005 and 2011, with a notable resurgence in wild bird mortality observed in 2016 across Western Europe.
• Passive monitoring data for USUV in Austria and Hungary between 2010 and 2016 were analyzed to understand its epidemiological trends.

Purpose of the Study:

• To investigate the prevalence and genetic diversity of Usutu virus in wild birds in Austria and Hungary.
• To determine the phylogenetic relationships of circulating USUV strains and identify potential sources of introduction or re-emergence.
• To assess the ongoing circulation and potential for strain exchange of USUV within Central Europe.

Main Methods:

• Passive surveillance of wild bird mortality for Usutu virus detection.
• Molecular identification and characterization of USUV through phylogenetic analysis of coding-complete genomes and partial NS5 protein gene sequences.
• Comparison of USUV genetic data from Austria and Hungary with previously reported European strains.

Main Results:

• In Hungary, 18 sporadic USUV cases were diagnosed between 2010 and 2015, with a significant increase to 12 cases in summer/autumn 2016.
• Two USUV cases were identified in blackbirds in Austria in 2016.
• Phylogenetic analysis revealed close relationships between earlier Hungarian USUV strains and the initial Austrian and Hungarian viruses, while 2016 strains clustered with Italian USUV sequences from 2009-2010.

Conclusions:

• The findings indicate continuous circulation of Usutu virus in Austria and Hungary.
• Evidence suggests ongoing exchange of USUV strains between Italy, Austria, and Hungary.
• The study highlights the dynamic epidemiology of USUV in Europe and the need for continued surveillance.