Credit USDA - 42 States Reporting HPAI
#16,882
Although the above map from the USDA doesn't show it yet, yesterday California became the 43rd state (plus the District of Columbia) to report HPAI H5 in wild birds since the start of 2022. Additionally, 37 states have reported outbreaks of HPAI in poultry.
While the number of poultry lost during the last major North American epizootic (2015) was higher (est. 50 million), the geographic spread of HPAI H5 this year is far greater. And unlike in 2015, wild birds have been severely affected by this new virus.
HPAI H5Nx has undergone numerous evolutionary changes since it last appeared in North America, reassorting in China and/or Russia in the summer of 2016, and reinventing itself many times since. Clade 2.3.4.4b HPAI H5 viruses have demonstrated the ability to (weakly) infect humans, and both have spilled over into mammals, often causing severe illness or death.
This new, improved, HPAI H5 virus not only shows an enhanced ability to persist well into summer - long after migratory birds have left for their high latitude roosting areas - it also affects a much wider range of avian species (see DEFRA: The Unprecedented `Order Shift' In Wild Bird H5N1 Positives In Europe & The UK).
And perhaps most ominously, HPAI H5 (both H5N1 and H5N5) have been detected above the arctic circle for the first time, suggesting they may be circulating - and potentially evolving - in the next batch of migratory birds that will fly south in the fall.
Granted, the following announcement from California's Department of Fish and Wildlife may seem like just another in a long list of similar announcements we've seen over the past 6 months. But coming as it does well into July - it is a reminder that HPAI H5 continues to defy expectations - and that makes this virus worthy of our continued attention.
I'll return with a brief postscript after the break.Avian Influenza Virus Detected In Wild Birds In California
July 14, 2022
Wildlife disease specialists have confirmed the presence of Highly Pathogenic Eurasian H5N1 Avian Influenza in three wild birds found in Colusa and Glenn counties.
The birds were collected by the U.S. Fish and Wildlife Service on July 5 during a mortality event at the Sacramento National Wildlife Refuge Complex and submitted to the U.S. Geological Survey’s National Wildlife Health Center for preliminary testing. On July 13, the U.S. Department of Agriculture’s (USDA) National Veterinary Services Laboratories confirmed the detection of avian influenza H5N1 in two Canada geese and one American white pelican and notified the California Department of Fish and Wildlife’s (CDFW) Wildlife Health Laboratory.
These are the first detections of avian influenza H5N1 in wild birds in California. Although avian influenza viruses naturally circulate among waterbirds, the strain of H5N1 currently in circulation in the U.S. and Canada has been causing illness and death in a higher diversity of wild bird species than during previous avian influenza outbreaks. The virus also remains highly contagious for domestic poultry. Currently, there are no confirmed cases of avian influenza in domestic poultry in California.
According to data compiled by the USDA(opens in new tab), avian influenza H5N1 has been detected in at least 1,825 individual wild birds in 42 states and the District of Columbia since January 2022. Additionally, infection has been confirmed in 386 commercial and backyard domestic poultry and mixed-species flocks in 37 states. Prior to its detection in North America, avian influenza H5N1 activity had been on the rise across Europe since October 2021.
Avian predators and scavengers may be exposed to avian influenza viruses when feeding on infected waterbirds. Infection with avian influenza viruses among songbirds, including many common backyard birds, appears to be rare. However, feeding and providing water to wild birds is discouraged, especially in the vicinity of backyard poultry or other captive birds such as ducks, geese, pigeons, doves and parrots. Increased concentration of wild birds at feeders and bird baths may lead to fecal contamination of the local environment, which may aid in disease transmission. Wild birds should be excluded from entering enclosures for domestic and pet birds, and food and water should not be shared between wild birds and domestic or pet birds.
CDFW’s Wildlife Health Laboratory, in coordination with partners, is continuing to monitor wild bird populations for signs of illness and investigating mortality events. The public may report dead wild birds using CDFW’s mortality reporting form. For guidance on orphaned or injured live wild birds, please contact your nearest wildlife rehabilitation center. Be advised that some wildlife rehabilitation centers may have restrictions on the wildlife species they will admit.
An informational flyer addressing frequently asked questions is available on CDFW’s website. Currently, the Centers for Disease Control (opens in new tab) considers the transmission risk of avian influenza to people to be low, but recommends taking basic protective measures (i.e., wearing gloves and face masks and handwashing) if contact with wild birds or domestic poultry cannot be avoided.
Practicing biosecurity is the most effective way to keep domestic poultry and pet birds healthy. Please visit the California Department of Food and Agriculture(opens in new tab) (CDFA) and USDA(opens in new tab) websites for biosecurity information. Sick and dead poultry may be reported to the CDFA hotline at 1 (866) 922-2473.
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While it was once believed that the Western Hemisphere was pretty well protected from Asian and European avian flu viruses by long distances and vast oceans, twice in the past 7 years we've seen HPAI H5 overcome those long odds and spark a major North American epizootic
As the USGS graphic below illustrates, the summer breeding grounds of Alaska lie under both the North American and Asian-Pacific flyways, and this is the presumed route that HPAI H5N8 took when it arrived in North America back in 2015.
Since it happened once, it could presumably happen again.
It is, of course, unknowable whether HPAI H5 will ever become a major threat to human health. H5N1 has loomed large before - even sparking modest human epidemics in Indonesia, Vietnam, and Egypt - only to evolve into a less virulent virus, and then recede into the night.
We may get lucky again.
But HPAI H5 is more widespread, and more genetically diverse now, than at any time since it emerged over 2 decades ago in Southeast Asia. It continues to throw the genetic dice, reinventing itself through antigenic drift and shift (reassortment), producing random, and unpredictable variants.
Which means we can't afford to become numb to the continued expansion of avian flu, and blithely assume that the H5 virus we will face tomorrow, or next year, will be no worse than the HPAI virus we face today.