Wednesday, April 17, 2024

CDC Guidance for Veterinarians: Evaluating & Handling Cats Potentially Exposed to HPAI H5N1

Cats As Potential Vectors/Mixing Vessels for Novel Flu


We've known for more than 20 years that cats are susceptible to certain types of novel flu (see HPAI: Catch as Cats Can), including H5N1. In 2006, the WHO reported:

In February 2004, the (H5N1) virus was detected in a clouded leopard that died at a zoo near Bangkok. A white tiger died from infection with the virus at the same zoo in March 2004.

In October 2004, captive tigers fed on fresh chicken carcasses began dying in large numbers at a zoo in Thailand. Altogether 147 tigers out of 441 died of infection or were euthanized. Subsequent investigation determined that at least some tiger-to-tiger transmission of the virus occurred.

Since then we've a number of spillovers of both LPAI and HPAI to cats, including:

In late 2016, New York City reported hundreds of cats across several city-run animal shelters contracted avian an LPAI H7N2 (see NYC Health Dept. Statement On Avian H7N2 In Cats)

Studies later showed that two shelter workers were infected whil5 others exhibited low positive titers to the virus, suggesting possible infection (see J Infect Dis: Serological Evidence Of H7N2 Infection Among Animal Shelter Workers, NYC 2016). 

More recently, the United States has reported a number of spillovers of HPAI H5N1 into cats (see Nebraska Veterinary Diagnostic Center (NVDC) Report: 2 Domestic Cats Infected With HPAI H5N1), and last year both South Korea and Poland reported significant outbreaks in felines. 

Two weeks ago, CIDRAP confirmed that 3 cats had tested positive for HPAI H5 on at least one of the Texas dairy farms where cattle have been infected, and Cornell University - whose Animal Health Diagnostic Center has done some of the preliminary testing - reported:

Grackles and pigeons were found dead at the same facilities, alongside some farm cats. While samples from cows were being sequenced, tests from the birds and a cat performed in the Molecular Diagnostics Laboratory at the AHDC came back positive for HPAI. Analysis of the NGS data then detected influenza sequences in the nasal swabs and milk samples from the sick cows.

We recently reviewed the CDC's Updated Advice On Bird Flu in Pets and Other Animals, which warned the public to avoid contact between their pets (e.g., pet birds, dogs and cats) with wild birds

This week the CDC has published the following recommendations for Veterinarians who may come in contact with potentially exposed cats. 

Considerations for Veterinarians: Evaluating and Handling of Cats Potentially Exposed to Highly Pathogenic Avian Influenza A(H5N1) Virus
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Highly pathogenic avian influenza (HPAI) A(H5N1) virus is an influenza virus that causes what is known as “bird flu.” Although bird flu viruses mainly infect and spread among wild migratory water birds and domestic poultry, bird flu viruses have been shown to spread, although inefficiently, to mammals, including humans.

HPAI A(H5N1) infections in cats have been reported in the United States, Poland, South Korea, and France. These cats demonstrated varying degrees of clinical manifestations, including respiratory and neurological signs, and some had fatal outcomes. Infection is thought to have happened via exposure to infected birds or other animals.
In late March and early April 2024, Texas reported detection of HPAI A(H5N1) in several cats from several dairy farms experiencing HPAI A(H5N1) virus infections in dairy cows, suggesting the virus spread to the cats either from affected dairy cows, raw cow milk, or from wild birds associated with those farms.

While it’s unlikely that people would become infected with bird flu viruses through contact with an infected wild, stray, feral, or domestic cat, it is possible—especially if there is prolonged and unprotected exposure to the animal. Sick animals may be able to transmit influenza virus to people in their saliva, feces or droppings, and other body fluids. Human infections can occur when the virus is inhaled or gets into a person’s eyes, nose, or mouth. This can happen when virus is in the air (in droplets or dust) and a person breathes it in, or when a person touches something that has virus on it and then touches their mouth, eyes, or nose.

Veterinarians and veterinary staff, in field and clinical settings, who are working in close contact with cats who are suspected or confirmed-positive for HPAI A(H5N1) virus infection, including those who are sampling cats for HPAI A(H5N1) viruses, should take precautions to prevent potential unprotected exposures.

Recommendations for Worker Protection and Use of Personal Protective Equipment (PPE) to Reduce Exposure to Novel Influenza A Viruses Associated with Severe Disease in Humans may be adapted to veterinarians and veterinary staff who will have exposure to cats that are suspected or confirmed with HPAI A(H5N1) virus infection. Recommendations from this resource are below. Criteria for exposure are described in: Highly Pathogenic Avian Influenza A(H5N1) Virus in Animals: Interim Recommendations for Prevention, Monitoring, and Public Health Investigations | Avian Influenza (Flu) (
  • Avoid unprotected close or direct physical contact with sick cats who may have been exposed to animals that tested positive for HPAI A(H5N1) virus infection.
  • When handling or interacting with cats that might be infected with or have been exposed to bird flu viruses, veterinarians and staff should wear PPE including:
    • Disposable or non-disposable fluid-resistant coveralls or gown*, and depending on task(s), add disposable or non-disposable waterproof apron
    • Any NIOSH Approved® particulate respirator (e.g., N95® or greater filtering facepiece respirator, elastomeric half mask respirator with a minimum of N95 filters)
    • Properly-fitted unvented or indirectly vented safety goggles** or a face shield if there is risk of liquid splashing onto the respirator
    • Rubber boots or rubber boot covers with sealed seams that can be sanitized or disposable boot covers for tasks taking a short amount of time
    • Disposable or non-disposable head cover or hair cover
    • Disposable or non-disposable gloves
* Preferably, fluid-resistant coveralls should be made of material that passes:
  • AATCC 42 ≤ 1 g and AATCC 127 ≥ 50 cm H2O or EN 20811 ≥ 50 cm H2O; or
  • ASTM F1670 (13.8 kPa); or
  • ISO 16603 ≥ 3.5 kPA
** Preferably, safety goggles should conform to ANSI Z87.1 that are marked at least Z87 D3
Use particular care during aerosol-generating procedures (i.e., intubation, dental procedures).

All PPE should be used in accordance with OSHA regulations found at 29 CFR 1910 Subpart I (Personal Protective Equipment) including identifying appropriate PPE based on a site-specific risk assessment. Workers must receive training on and demonstrate an understanding of when to use PPE; what PPE is necessary; what it looks like when PPE is properly fitted; how to properly put on, use, take off, dispose of, and maintain PPE; and the limitations of PPE.

Guidance for people exposed to birds that test positive for HPAI A(H5N1) can be considered for people exposed to cats or other animals that are suspected or confirmed with H5N1:
People exposed to HPAI A(H5N1)-infected birds or other animals (including people wearing recommended PPE) should be monitored for signs and symptoms of acute respiratory illness beginning after their first exposure and for 10 days after their last exposure.

N95 and NIOSH Approved are certification marks of the U.S. Department of Health and Human Services (HHS) registered in the United States and several international jurisdictions.

Last Reviewed: April 15, 2024
Source: Centers for Disease Control and Prevention, National Center for Immunization and Respiratory Diseases (NCIRD)

While cat-to-human transmission of influenza viruses has only rarely been documented, HPAI H5 continues to exceed our expectations, and some extra precautions are warranted.