Outbreaks of highly pathogenic avian influenza (H5N2) in Italy during October 1997 to January 1998

Between the month of October 1997 and January 1998, eight outbreaks of highly pathogenic avian influenza were diagnosed in the Veneto and Friuli-Venezia Giulia regions in north-eastern Italy. For each of the eight outbreaks, influenza A virus of subtype H5N2 was isolated and the inoculation of susceptible chickens confirmed these viruses to be extremely virulent with intravenous pathogenicity indices in 6-week-old chickens of 2.98 to 3.00. Although it was not possible to trace the origin of infection, the epidemiological investigation revealed connections between several outbreaks and emphasized the well-known risk factors for avian influenza such as bird movement, rearing of mixed populations and contact with migratory waterfowl. Control measures listed in European Union directive 92/40/EEC were implemented promptly and spread of the infection to intensively-reared domestic poultry was avoided.