Wild waterfowl and avian influenza

A study suggests that undiscovered mechanisms may prevent wild waterfowl from sustaining highly pathogenic (HP) avian influenza viruses (AIV). In 2014-2015, HP H5Nx AIV with genetic origins in Eurasian and North American wild bird populations led to a widespread North American poultry outbreak, resulting in an estimated economic toll of $5 billion in the United States. To investigate the role of wild waterfowl in perpetuating HPAIV, Robert Webster and colleagues tested more than 22,000 wild aquatic birds in North America for HP H5Nx viruses before, during, and after the poultry outbreak. Wild waterfowl tested positive for HP H5Nx influenza A virus during—but not before or after—the outbreak. Furthermore, a review of historical aquatic bird influenza A virus surveillance observations from North America found that although H5Nx viruses with low pathogenicity are routinely detected in wild waterfowl, the birds have not tested positive for HP H5Nx viruses during the past 43 years, with the exception of the 2014-2015 outbreak. The findings suggest that undiscovered mechanisms may restrict the emergence and perpetuation of HPAIV in wild aquatic bird populations. According to the authors, strategies to eradicate HPAIVs in poultry, such as culling, quarantines, and increased biosecurity, may complement natural mechanisms that curb the spread of AIVs. - Read at PNAS.org

Article #16-08853: “The enigma of the apparent disappearance of Eurasian highly pathogenic H5 clade 2.3.4.4 influenza A viruses in North American waterfowl,” by Scott Krauss et al.