‘Exclusively indoor’ cats may have caught bird flu from their owners
Key takeaways:
- Bird flu was detected in two indoor domestic cats with respiratory and neurologic illness.
- The cats lived with dairy workers with no known exposure to bird flu but who declined testing.
Two indoor cats in Michigan died after being infected with bird flu that they may have contracted from their owners who work as dairy workers, according to a CDC report.
“Highly pathogenic avian influenza (HPAI) A(H5N1) virus ... has been documented in cats on U.S. dairy cattle farms,” Ramya Naraharisetti, PhD, an Epidemic Intelligence Service officer at CDC, and colleagues wrote in an MMWR report.
“In May 2024, the detection of HPAI A(H5N1) virus infection in two cats that were reported to be exclusively indoor, and that had respiratory and neurologic illness in different households, prompted an investigation by the Michigan Department of Health and Human Services and Mid-Michigan District Health Department,” they wrote.
According to the report, the first of the two cat deaths was from a household with three exclusively indoor cats. The 5-year-old female cat began showing symptoms including lack of appetite, lethargy and neurologic disorientation. The cat was taken to a local vet and referred to the Michigan State University (MSU) Veterinary Medical Center, where it was ultimately euthanized due to "rapid disease progression.” Swabs from the cat's brain and nose came back positive for H5N1 and matched the viruses circulating in local dairy cattle.
A broader investigation was launched during which health officials discovered that another cat in the household developed symptoms associated with bird flu after the first cat. This cat ultimately recovered and no additional testing for H5N1 was conducted.
The owner of the two cats worked on a dairy farm — although not directly with animals — and reported experiencing vomiting and diarrhea before either of the cats’ illnesses. They did not undergo testing to confirm H5N1, however.
Within a week of the first cat being referred to MSU, a second indoor cat from a different household began exhibiting symptoms and was taken to the veterinary medical center. The 6-month-old male cat had “progressive neurologic deterioration,” lethargy, facial swelling and had stopped eating. It died within 24 hours of symptom onset. Nasal swabs collected from the cat were positive for H5N1, according to the report.
The owner of the second cat was a dairy worker who transported unpasteurized milk. They told investigators that they did not wear personal protective equipment (PPE) while handling the milk and reported frequent “splash exposures” to the face, eyes and clothing. They also said that the cat that died would roll in their possibly exposed clothing, while a second cat in the home did not exhibit that behavior and never showed any symptoms.
The investigation also revealed that the owner developed eye irritation before the cat’s sickness began. However, they declined testing for bird flu and treatment with oseltamivir and declined further contact with public health officials for “fear of losing employment as a consequence of communicating with public health officials and implicating farms that provided milk.”
Based on the findings of the investigation, the authors wrote that farm workers are encouraged to consider removing clothing and footwear and to rinse off any animal byproduct residue — such as milk or feces — before entering households. They added that veterinarians evaluating cats with signs of respiratory or neurologic illness in areas where bird flu is circulating are recommended to wear PPE when examining these animals or collecting specimens for testing.
These cat deaths are not the first associated with the ongoing bird flu outbreak.
In July, a CDC report examining dairy cattle and cats at farms in both Kansas and Texas showed “fatal and systemic influenza infection” in domestical cats on the farms who were given unpasteurized colostrum, a milk from affected cows. The symptoms included neurologic signs of illness and blindness.
The authors of the report wrote that the cats were found dead with no apparent injury and that tested samples suggested “high amounts of virus."
In a statement on its website, the American Veterinary Medicine Association wrote that cats “appear to be particularly susceptible to severe illness” and infection often results in death.
“Whether infected cats can infect other cats is currently unclear; however, that possibility cannot be dismissed,” the site read. “The risk of cat-to-human transmission is considered extremely low but may increase with prolonged, unprotected exposure to infected animals.”
References:
- AVMA. Avian influenza A (H5N1) in cats. https://www.avma.org/resources-tools/animal-health-and-welfare/animal-health/avian-influenza/avian-influenza-h5n1-cats. Accessed Feb. 20, 2025.
- Burrough ER, et al. Emerg Infect Dis. 2024;doi:10.3201/eid3007.240508.
- Naraharisetti R, et al. MMWR Morb Mortal Wkly Rep. 2025;doi:10.15585/mmwr.mm7405a2.
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Naraharisetti R, et al. MMWR Morb Mortal Wkly Rep. 2025;doi:10.15585/mmwr.mm7405a2.