People can give their cats bird flu, CDC study suggests

Bird flu may be spreading between people and cats more than previously thought, a new federal study said.

The findings published Thursday by the Centers for Disease Control and Prevention’s weekly journal add to worries about the spread of highly pathogenic avian influenza from people to cats and vice versa.

The study looked at indoor cats who had severe illness and death in two Michigan households of two dairy workers around May where bird flu was circulating on farms. Both lived in the same county, and both took sick cats to the Michigan State University Veterinary Medical Center. The study mentioned one household where an adolescent developed a cough and other symptoms after a cat became sick, but the results were inconclusive since the teen also had additional exposure.

The findings are a cause for alarm that should be taken seriously, said Kristen Coleman, an assistant professor at the University of Maryland School of Public Health who has tracked cat deaths from bird flu, also known as H5N1.

"It's scary to think of how much worse it could get," Coleman, who was unaffiliated with the study, told USA TODAY. "This adds another layer of complexity in the control of this virus."

Bird flu has been known to cause severe illness and deaths in cats, often through raw food or milk or dead birds. However, the study provides growing evidence of the threat it poses even when cats have no direct exposure to sick dairy cows or poultry.

The two cats that died, one in each household, appeared to have the same signs of respiratory and neurologic illness, according to the study, published by CDC researchers, as well as health and agriculture officials from Michigan and Michigan State University. The cats later tested positive for bird flu, also called highly pathogenic avian influenza.

The first household’s cat, the 5-year-old female, was euthanized four days after signs of illness, and the second household’s cat, the 6-month-old Maine Coon cat, died within a day of illness showing.

People in the homes also displayed symptoms of illness. Neither worker in each household received testing or antiviral medication for bird flu, and the second worker feared losing employment as a consequence of speaking with public health officials and implicating farms that provided milk, the study said.

Like pigs, cats can carry both avian and human influenza viruses. If both viruses were to appear in one host, the bird flu virus could mutate into a pathogen that's more easily transmissible among humans. This hasn't been the case, yet, but researchers note the study's findings could be a cause for concern. So far, nearly 70 people have contracted bird flu, mostly among dairy and poultry workers, and one person has died, according to CDC.

The study also appears to be the same that had a graphic released on CDC's Morbidity and Mortality Weekly Report (MMWR) before it was abruptly taken down earlier this month, as The New York Times reported. Since President Donald Trump has taken office, there have been delays in releasing MMWR reports, considered an eminent scientific publication for researchers around the world, amid cuts to health agencies.

The study is difficult to interpret how transmission is occurring among people in both households given gaps in testing, said Benjamin Anderson, an assistant professor at the University of Florida’s College of Public Health and Health Professions who researches emerging pathogens. It also speaks to a slow U.S. public health response to bird flu, which began in the Biden administration and is now under Trump.

Anderson, who was not affiliated with the study, said the study examined cases in May and testing of people presumably occurred soon after, but the MMWR only released in February.

“The delays and gaps of information are, again, highlighting just how challenging it has been to respond to this thing,” Anderson said. “We're basically blind.”

What did bird flu and cats study show?

The first worker, who didn’t directly work with animals but worked on the farm, would remove work clothes and boots and place them in an area away from the household’s indoor cats. In the first household, the worker lived with another adult and two adolescents, along with the sickened 5-year-old female cat and two other indoor cats.

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A day before the 5-year-old female cat would get sick, the worker had one day of vomiting and diarrhea. One adolescent in the household developed cough, sore throat, headache and muscle aches and pain six days after the 5-year-old cat had become sick. Three of the household members tested negative for influenza, but the sickened adolescent had a positive lab result for rhinovirus and enterovirus, which are different than bird flu. The dairy worker had regular contact with the sick 5-year-old cat and the sick adolescent.

Four days after the 5-year-old cat became sick, another cat had watery eyes and discharge, increased breathing and decreased appetite, though these resolved four days later. The third cat never showed signs and tested negative.

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Meanwhile, the second worker transported raw milk and reported that their job frequently had raw milk splash exposure to face, eyes and clothing without personal protective equipment. The worker would bring work clothes indoors, where one indoor cat would roll in the clothes. The worker did experience eye irritation two days before illness showed in the indoor cat.

The second household had the second worker, the 6-month-old male cat, and a second indoor cat. The second indoor cat didn’t show signs of illness and nasal swabs tested negative for virus.

Bird flu's risks ahead

The study calls for increased consideration by veterinarians for pet owners’ occupational information, as well as testing for influenza viruses, and wearing PPE.

There have been prior incidents of cats spreading bird flu to people, if rare, and not knowingly in households. In 2016, a cat in a New York City shelter spread a different bird flu virus to a person, as CDC reported. But in 2004, people at a Thai zoo had positive antibodies results for H5N1 after tigers were infected and died in captivity.

"If this was potentially happening 20 years ago, and now it's happening in households, that's pretty alarming," Coleman said.

Contributing: Adrianna Rodriguez

This story has been updated with new information.

This article originally appeared on USA TODAY: Bird flu spreads between people and cats, says CDC study