What we’re watching: Highly Pathogenic Avian Influenza Virus H5N1

The United States Department of Agriculture (USDA) is currently tracking a highly pathogenic avian influenza (HPAI) virus that was first detected in South Carolina, in a wild bird, in mid-January, 2022. As of Wednesday, March 2, 2022, at least nine states – Indiana, Kentucky, Virginia, Maine, New York, Delaware, Michigan, Iowa and Connecticut – have reported cases in commercial poultry operations and backyard birds. 

As all of us realize, however, the dynamic spread of this virus could change. We are closely monitoring the situation, but do not believe this will become the next pandemic in the human or mammalian populations. 

Here’s what you need to know:

The current risk of this infection to the general public is considered low at this time. Farm workers, people with close contact with domestic animals, and hunters are reminded to follow biosecurity measures. 

This current strain of HPAI is influenza A (H5N1). The HPAI that tore through the United States and Canada affecting chicken, egg and turkey farms in 2014-2015 was the novel HPAI A (H5N2) strain. The origins of H5N2 were more than likely from migratory waterfowl that were infected with H5N8 from Asia and landed in western portions of the United States and Canada, as that is where it was first detected. Then, the H5N8 virus was reassorted with North American low pathogenic avian influenzas (LPAI). The result was a new reassortment of the H5N2 virus (Asian H5, North American N2).

The USDA does announce the first case of HPAI in commercial and non-commercial backyard flocks detected in a particular state, but does not announce subsequent detections within that state.

Flocks with detected HPAI will never be allowed to enter the food chain system. 

The USDA and Centers for Disease Control and Prevention (CDC) remind everyone about the proper handling and cooking of poultry and eggs in order to reach the internal temperature of 165˚F that kills bacteria and viruses, including HPAI A(H5) viruses.

Infected birds shed avian influenza A viruses in their saliva, nasal secretions, and feces.

Wild birds can carry HPAI A(H5) viruses without showing symptoms, but these viruses can cause illness and death in domestic poultry.

Has any strain or variant of H5N1 infected humans?

Yes. Since 2003, 19 countries have reported more than 860 total human infections with H5N1 viruses to the World Health Organization (WHO). Approximately 53 percent of those resulted in death. Many of the people infected had close or prolonged unprotected contact with infected birds or contaminated environments. Additionally, those reported cases oftentimes presented late for adequate medical care. 

Illnesses in humans from avian influenza A virus infections have ranged from mild (e.g., eye infection, upper respiratory symptoms) to severe illness (e.g., pneumonia). The spread of avian influenza A viruses from one sick person to another is very rare, and when it has happened, it has not led to sustained spread among people.

What about companion dogs and cats contracting H5N1?

In laboratory experiments — the short answer is “yes”. Clinical signs in infected cats have not been extensively described, but include fever, listlessness, conjunctivitis, difficulty breathing, and occasionally death. Dogs presented with anorexic, fever, conjunctivitis, labored breathing, coughing, and death. These signs are commonly encountered along with other respiratory disease syndromes of dogs or cats, so laboratory confirmation of HPAIs is necessary for a definitive diagnosis.

However, we should really focus on confirmed, naturally occurring, clinical cases. 

During a previous outbreak in Germany in February, 2006, only feral cats were shown conclusively to be naturally infected with H5N1. It is suspected that these cats became infected after eating infected wild birds. Anecdotal reports (i.e. not confirmed by laboratory testing) noted an increased mortality in cats during H5N1 outbreaks in other countries.

In a 2005 unpublished study conducted by the National Institute of Animal Health in Bangkok, researchers tested 629 village dogs and 111 cats in a particular area of Thailand. Out of these, 160 dogs and 8 cats had antibodies to H5N1, which indicates that they were infected with the virus or had been infected in the past.

Can I give my companion dog or cat H5N1?

There is no evidence at this time to support the zoonotic spread of H5N1 from infected humans to companion pets. Remember, human-to-human transmission is very low as well. Also remember, the infected feral cats probably had eaten an infected wild bird.

What about my companion dog or cat passing it H5N1 to me?

Current science suggests that the risk of a human contracting H5N1 from a companion pet is very low. 

Remember, the onus is on us to protect our pets. Walk your companion dog on a leash, keep him away from dead birds, and do not let him eat bird poop. 

For cats, please keep them inside or walk them on a leash. 


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“News and Announcements.” Animal and Plant Health Inspection Service, U.S. Department of Agriculture, https://www.aphis.usda.gov/aphis/newsroom/news.  

Pasick, John et al. “Reassortant highly pathogenic influenza A H5N2 virus containing gene segments related to Eurasian H5N8 in British Columbia, Canada, 2014.” Scientific reports vol. 5, 9484. 25 Mar. 2015, doi:10.1038/srep09484, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4372658/

“Pets and Highly Pathogenic Strain H5N1 Avian Influenza.” Canadian Food Inspection Agency, Gouvernement Du Canada, 26 Feb. 2021, https://inspection.canada.ca/animal-health/terrestrial-animals/diseases/reportable/avian-influenza/pets-and-h5n1/eng/1375992449648/1375992451039

Recent Bird Flu Infections in U.S. Wild Birds and Poultry Pose a Low Risk to the Public. Centers for Disease Control and Prevention, 14 Feb. 2022, https://www.cdc.gov/flu/avianflu/spotlights/2021-2022/bird-flu-poses-low-risk-public.htm

Updated: H5N1 Bird Flu Virus in U.S. Wild Birds and Poultry Poses a Low Risk to the Public. Centers for Disease Control and Prevention, 22 Feb. 2022, https://www.cdc.gov/flu/avianflu/spotlights/2021-2022/updated-bird-flu-poses-low-risk.htm.

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