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Influenza Surveillance in Wild Birds

Wild waterfowl are recognized as the major reservoir for influenza A viruses which can infect poultry, swine, and humans. Waterfowl often show no clinical signs when infected with the virus making them a good source for transmission. Influenza A is an enteric virus in waterfowl, which means that it infects their digestive system, in contrast to the respiratory infection in humans and other animals. This enteric infection of waterfowl causes the virus to be passed in their feces, allowing for wide spread transmission within the waterfowl population and to other species during the annual bird migration.

Commercial and domestic poultry are particularly susceptible to the viruses passed by waterfowl. In chickens, influenza A viruses are classified as Low Pathogenic Avian Influenza (LPAI) and High Pathogenic Avian Influenza (HPAI). LPAI viruses tend to cause only minor illness and little to no mortality in chickens while HPAI viruses cause major illness and high mortality. Both LPAI and HPAI present major threats to the commercial poultry industry. Though LPAI present little immediate threat, influenza A viruses can rapidly mutate and LPAI viruses could mutate to HPAI viruses, leading to major commercial losses. Infection in a commercial flock often leads to large amounts of culling.

Influenza A infection of waterfowl and chickens also presents an infection risk to humans. One example of this is the current LPAI H7N9 endemic in China. With thriving live bird markets, chickens infected with the LPAI H7N9 virus and showing no signs of infection are transmitting the virus to humans handling them. According to the CDC, 40% of those infected have died and, even though there has been limited evidence of human-to-human transmission, H7N9 presents the greatest risk for a global pandemic.

In order to keep an eye on the influenza A viruses circulating the waterfowl in the United States, our program does yearly surveillance during the annual bird migration. With the help of collaborators, wildlife biologists, and numerous hunters, we are able to collect thousands of samples from waterfowl each migration.

  • Gain insight into how antigenic and genomic diversity of influenza A viruses are maintained in wild bird populations.

  • Add to a baseline from which to detect the appearance and emergence of unique or rare genomic segments or constellations that potentially could present an increased threat to animal and human health.

  • Expand the wild bird-origin influenza A virus repository.

  • Submit isolates to NVSL for full length sequencing and subsequent placement of sequence data into GenBank and the IRD for use by scientists around the world.

  • Merge data from previous years to draw conclusions regarding influenza A viruses circulating in wild birds in the migratory flyways.

Take a look at some of our 2016-2017 Migration data below!