Avian Influenza

Recent months have seen much information in the news about avian influenza, the H5N1 virus, and its impact on people and birds. The important facts to know are:

  • “Avian flu” is one of several dozen viruses in the Type A influenza group. They are distinguished from one another by their serotypes, such things as H5N1, H3N2, H7N4, etc. Some of these viruses, such as the H3 type, infect  humans, swine and dogs; others preferentially infect horses or even porpoises. Some can infect several species, although they typically have a preference for one type of host, e.g., bird or human.  Additionally, both low pathogenicity (LP)_ and high pathogenicity (HP) forms exist for many, particularly those of the H5 and H7 lineages.  Waterfowl, especially ducks, are the natural reservoirs for all Type A influenza viruses and the viruses circulate quietly in their populations (i.e. cause no discernible disease).

  • Previously (2000 – 2014) concern laid with the HP H5N1 serotype which has remained confined, so far, to Asia and Europe where to this day it is causing mortality in wild birds, poultry and humans.

  • The H5N1 virus is particularly lethal for chickens. In areas of the world where free-ranging chickens are allowed to mingle with wild waterfowl, there has been significant direct and indirect mortality in chickens, the latter through culling to limit spread. Millions of chickens have been killed in Southeast Asia in to control the spread of the disease.

  • The virus is not vector-borne like West Nile virus. Mosquitoes and other insects are not involved in its transmission.

  • In the spring of 2015, two new HP H5 viruses appeared in North America.  Introduced originally as an H5N8, previously seen in the summer and fall of 2014 in Korea and Japan, it combined with other North American influenza viruses and generated a new HP H5N2 strain.

  • It is most likely that a circumpolar migrant water bird such as a widgeon or pintail duck carried the virus from Asia to North America. In December of 2014, the H5N8 virus was “discovered” in Washington State by falconers that were hunting local ducks; several trained gyrfalcons died of the virus; additionally, several backyard poultry flocks encountered the virus and were destroyed.

  • In March of 2014, a turkey flock of some 20,000 birds in Pope County, MN were infected; most birds died and the remainder were destroyed.  The virus  was found to be a HP H5N2 strain.

  • Subsequently, there was massive infection of domestic poultry in the Mississippi Flyway resulting in the direct death or destruction of over 40 million chickens and turkeys.

  • Only two raptors, a coopers hawk and a snowy owl are known to have died from this round of influenza.

  • Neither the H5N8 or H5N2 viruses have demonstrated any capacity to infect humans, however poultry farm workers at sites where there have been outbreaks are being monitored.

How The Raptor Center is responding

Presently, scientists at The Raptor Center and the University of Minnesota College of Veterinary Medicine are developing, in conjunction with the Minnesota DNR and the USDA, widely scale surveillance projects to monitor the circulation of the H5N2 virus in waterfowl. In addition, all bald eagles, peregrine falcons, great horned owls, red-tailed hawks and barred owls admitted to TRC for whatever reasons, species known to prey to a greater or lesser extent on waterfowl, are being sampled for evidence of infection with influenza viruses.

Please forward any questions you have to Dr. Patrick Redig, at redig001@umn.edu.

Find out more

Download or view the American Association of Avian Pathologists Asian Bird Flu handout

To keep track of the current status of avian influenza, visit these websites:

For more information about avian influenza in poultry, visit the University of Minnesota College of Veterinary Medicine's avian influenza Web page.