Emergence and Selection of a Highly Pathogenic Avian Influenza H7N3 Virus
Nancy Beerens, René Heutink, Frank Harders, Alex Bossers, Guus Koch, Ben Peeters
Abstract
Low-pathogenicity avian influenza (LPAI) viruses circulate in wild birds and can be transmitted to poultry. LPAI viruses can mutate to become highly pathogenic avian influenza (HPAI) viruses causing severe disease and death in poultry. Little is known about this switch to high pathogenicity. We isolated an LPAI H7N3 virus from an infected turkey farm and showed that this contains small amounts of HPAI virus. The HPAI virus rapidly outcompeted the LPAI virus in chickens that were experimentally infected with this mixture of viruses. We analyzed the genome sequences of the LPAI and HPAI viruses and identified several changes that may be important for a virus to become highly pathogenic. This knowledge may be used for timely identification of LPAI viruses that pose a risk of becoming highly pathogenic in the field.