Parasites and Diseases
West Nile Virus

West Nile Virus Surveillance of Wild Birds in Alaska

Currently there is no longer a program capacity to conduct surveillance for the occurrence of West Nile Virus in wild birds in Alaska. However, if a large die-off of birds is reported to any of the wildlife agencies, general disease investigations would include testing for this disease if circumstances warranted.


West Nile Virus (WNV) was first detected in the Western Hemisphere in New York in 1999. This mosquito-borne virus can cause disease in both human and animals but particular species of birds as well as horses are the most likely to become severely ill or die from the virus. The vast majority of people infected from mosquito bites develop only mild symptoms and never even realize they have been infected with WNV. Even with almost 4000 human cases in the US documented, only about 200 deaths occurred. However, the disease is much more serious for birds and horses than people. In 2002, the disease continued to spread across North America with increasing morbidity and mortality among bird and horse populations. As of 2016, Alaskan public health authorities have yet to record case of locally-acquired WNV in humans.

Although we expect to eventually detect the infection in birds migrating to Alaska, WNV may be slower to become established in Alaska's birds than elsewhere for several reasons. Birds that serve as WNV reservoirs must be viremic (have lots of virus in the blood stream) at the time they are bitten by a particular type of mosquito that will also bite mammals. The time the virus is in the bird's blood is brief and transient (believed to be about 2 to 4 days); therefore, many birds migrating to Alaska from an area where the disease is established are likely to have cleared the virus before arrival in Alaska. As well, the mosquito species that are the most efficient vectors (transmitters) of WNV in the Lower 48 are not present in Alaska. Finally, it appears that mosquitoes require sustained warm temperatures, that rarely occur in Alaska, to have the virus grow in numbers to make them infective to their next bite victim. Locally acquired WNV could occur only if viremic migratory birds arrive in Alaska when the appropriate species of mosquitoes are active and when temperatures would permit adequate amplification of virus. With all those factors in place, virus could potentially spill over into non-migratory birds, humans, horses, or other Alaskan animals.

Bird species impacted by WNV

Although most bird species can be infected by WNV, some act as reservoir or amplifying hosts, and a few species die quickly. The bird species in Alaska that are most likely to become recognizably ill or die from WNV include the following: Raven, Crow, Magpie, Steller's jay, Gray Jay, Blue Jay, Eagles, Falcons, Hawks, and Owls.

To report a sick or dead bird

If you find a dead bird of the above species and or a group of dead birds of any species, DO NOT PICK UP THE BIRD. Please call the USFWS Bird Mortality Hotline at: 1-866-527-3358. NOTE: Birds suspected to have been electrocuted, shot, poisoned, or otherwise killed under suspicious circumstances should be reported immediately to the USFWS Law Enforcement Division at 800-858-7621; or, if in Anchorage, at 907-271-2828.

Method of carcass disposal

If instructed by a wildlife or public health authority to dispose of a dead bird, use gloves or put your hand inside of a plastic bag to pick up the bird. Double bag the carcass and dispose of it in the garbage.

Surveillance in other wildlife

Investigation of sick or dead wildlife will be handled as always on a case-by-case basis. Please contact the ADF&G Wildlife Disease Surveillance and Information hotline 907-328-8354 or email .

For More Information Specific to Alaska

More General Information on West Nile Virus in Wildlife