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By Dr. Amber Itle, Washington State Veterinarian
Who would have guessed that the one thing that all of these species would have in common in the last year is avian influenza. The yellow brick road has been full of surprises, spillover events, massive surveillance efforts, and federal orders. Here we are almost three years into this outbreak and we are still trying to find the Wizard to eradicate HPAI from the United States. Here are the top 10 high level updates on what we know about the virus, the birds, animals and humans it has impacted, and trends across the United States and here at home in Washington.
- The Virus
- In the US, every time HPAI is detected in any species, whole genomic sequencing is completed to better understand pathogenicity, changes in sequences and transmission patterns.
- There are currently three predominate strains of Eurasian HPAI H5 2.3.4.4b circulating in the United States A3, D1.1 (wild bird) and B3.13 (dairy cattle). Interestingly, Washington State had the first detection of the D1.1 genotype in the Fall of 2024. Since then, A3 and D1.1 have become the predominate genotypes in wild birds and wild mammal detections across the US.
- The B3.13 genotype is the only one with any indication of mammal to mammal transmission from a viral standpoint. Carnivorous mammals including cats are dead end hosts. The D1.1 and B3.13 have both infected cats through ingestion of infected birds or consuming raw milk/ contaminated raw food.
- Transmission of the wild bird strain is primarily from migratory waterfowl.
- Transmission of the dairy genotype occurs directly cow to cow and indirectly via fomites. Breaches in biosecurity including sharing of contaminated equipment, trucks, and even workers are implicated in the rapid spread of the disease within a dairy shed. Infected peridomestic animals and wind events near infected farms may all play a role in transmission to nearby farms. Spillover from dairies to poultry facilities in close proximity is complicating this issue more.
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The Chickens
- The Cows
- In March 2024, USDA announced spillover of highly pathogenic avian influenza (HPAI) clade 2.3.4.4b virus into lactating dairy cattle due to a single point source introduction. This emergent genotype, B3.13, appears to have an affinity for the mammary tissue of cattle. As of January 24, 2025, the virus spread to 939 herds in 17 States.
- There are no confirmed or suspected livestock or poultry cases of B3.13 in Washington state. The Washington State Veterinarian’s office is working closely with the dairy industry to support an ongoing statewide surveillance program for every dairy statewide at 3-4 week intervals. To date, over 200 dairies in the state have been tested at least once, but the majority of dairies have tested negative at least 3 times.
- The Cougars
- H5N1 viruses have been detected in wild, captive, and domestic cats in several statesin the last few months causing severe neurologic and respiratory disease and death. In December 2024, a private, captive wild cat sanctuary in Washington reported a mortality event associated with HPAI in 21 cats (Tigers, Cougars, Servals, etc). Despite sampling of available raw feed sources at this facility, results have been negative to date. Investigations into recent captive wild cat cases of HPAI are ongoing, with state and federal partners collaborating with the private veterinarians to better understand the virus’s transmission.
- The Cats (and Dogs)
- There are 78 detections in domestic cats. There have been reports of a range of clinical signs and may even be some evidence of recovery.
- On December 24, 2024, the Oregon Department of Agriculture announced the detection of H5N1 Highly Pathogenic Avian Influenza (HPAI) in a domestic cat in Washington County, Oregon, and the subsequent recall of Northwest Naturals raw pet food that is believed to have been the source of infection. The CDCand FDA do not recommend feeding raw pet food or treats or raw milk to dogs and cats.
- To date, no domestic cats or dogs in Washington have tested positive for HPAI. WSDA can support testing of domestic cats at WADDL with consistent history and clinical signs. All neurologic cats will be tested for rabies first.
- Dogs can also contract HPAI, although they usually exhibit mild clinical signs and low mortality compared to cats. At present, HPAI has not been detected in dogs in the United States.
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The Wild Birds
- USDA Wildlife Services (WS) has historically collected H5N1 samples on hunter/harvest wild bird and reports of mortality/morbidity. In the fall year after year we start to see the surge with return migration and additional sampling efforts. This Fall 2024, WS confirmed 11,000 HPAI detections in wild birds across the 4 flyways with 13-14% positivity. The good news is that USDA has confirmed that the cattle genotype B3.13 has not been detected in healthy migratory bird surveillance, but birds and other peridomestic species in and around infected premises have tested postive.
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The Wild Mammals
- USDA Wildlife Services also has been tracking over 479 detections of clade 2.3.4.4b virus in 35 different mammalian species since the beginning of the outbreak in 2022. The Washington Dept of Fish and Wildlife reported positive HPAI cases in several species of birds, raccoons, cougars and seals in the fall of 2024.
- WS completes targeted surveillance around infected dairy/poultry facilities found infected peri-domestics on some facilities and not at all on others nationwide. The virus shows some evidence of being sustained in mice without continuous reintroduction. To date, USDA WS reports 33 positive peri domestics from an investigation on a positive Washington premises that included a raven, coyote, deer mice, European starlings, house mice, house sparrows and rock pigeons. Viral reintroduction from these species to poultry is a real concern.
- The Humans
- According to CDC, the risk of bird flu to the general public is low. CDC has been proactively conducting human surveillance with 89,000+ samples tested negative for influenza A (H5), 12,700+ high risk individuals monitored and 580+ people tested after exposure to infected animals. To date, 67 people have tested positive for HPAI in the United States. Of those, 23 were infected following exposure to infected poultry farms (11 of those in Washington State), 40 were infected following exposure to infected dairy cattle, two people were infected with unknown exposure. There has been one reported mortality in an individual with co-morbidities. There is no indication that markers have changed to make humans more susceptible.
- Washington state has PPE in stock and can make it available to commercial poultry/ dairy facilities upon request for farms with sick animals or a detection of H5N1. Currently, available PPE includes disposable gloves, face masks, and eye protection including safety goggles, safety glasses, and face shields. This is a one-time provision of PPE.
- The Reporting
- For pets: Contact WSDA Animal Health at ahealth@agr.wa.gov or 360-902-1878. WSDA may support paying for testing of highly suspicious cases.
- For backyard flocks or dairy cows: Report unusual illness or mortality to WSDA at 1-800-606-3056.
- For Veterinarians: report suspicious cases on the WSDA Reportable Animal Disease platform or contact your regional veterinarian.
- For wild birds or wildlife: Report using WDFW’s online reporting tool.
- For animal food: Contact WSDA Animal Feed Program at animalfeed@agr.wa.gov or 360-902-1844.
- The Wizard??
- The United States has the strongest avian influenza surveillance program in the world in domestic poultry, wild birds, livestock and humans.
- The dairy response to HPAI includes the April 2024 Federal Order requiring Interstate Movement Testing and Reporting to limit the spread between dairies, financial incentives and reimbursement for producers, additional testing, monitoring and biosecurity implementation.
- In November, USDA rolled out The National Milk Testing Strategy (NMTS) facilitates comprehensive H5N1 surveillance of the Nation’s milk supply and dairy herds. Specifically, the NMTS gives States a five-stage roadmap to demonstrate the elimination of this virus from their dairy herds. Washington just submitted a request to USDA for stage 4 status.
- USDA has updated several rules and policies including the HPAI Biosecurity audit tool, the Pre-slaughter testing pilot for turkeys in MN and SD and identifying Split Premises policies to promote business continuity, prevent reinfection, ensure consumer confidence and secure trade.
- USDA is moving forward with conversations about HPAI vaccination planning and scenarios for certain sectors of poultry and dairy cattle. Workgroups are being established to explore the feasibility to operationalize, logistics/ finances and how we might do surveillance to minimize impacts to trade.
- The Washington Animal Disease Diagnostic Laboratory (WADDL) is one of Washington’s most important “Wizards” supporting surveillance, detection and research to better understand the impacts. WADDL collaborates closely with state and federal agencies to actively monitor, understand, and mitigate the spread of highly pathogenic avian influenza virus (HPAI H5N1) across dairy cattle, poultry, and other animal species. HPAI tests performed from January 1, 2024, to present can be seen here: Testing for Highly Pathogenic Avian Influenza Virus | Washington Animal Disease Diagnostic Laboratory | Washington State University
It has been a long journey on the yellow brick road. WSDA continues to work with our “Lollipop Guild” that includes USDA, private veterinarians, academic partners and sister agencies to evolve key strategies, make science-based decisions. We all remain hopeful that the virus will change just enough to let us all get back to the normal, that we know as “home” with the courage of the Lion, the growth mindset of the Scarecrow and the passion of the Tinman.
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