We’re regularly rounding up the latest news on bird flu. Here’s what happened recently.
At a Glance
Human cases: No new cases reported. There have been 70 confirmed and seven probable cases since 2024.
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Poultry cases: February saw 12.7 million domestic birds either infected with avian influenza or culled in response to an infection. The number is just more than half of January’s tally. To date, March has seen 220,000 birds die.
Dairy cattle cases: California has reported six new herds of dairy cattle infected with avian influenza this month, bringing the national total to 983 herds infected since the current outbreak began.
Infections in Cats
Bird flu infections in domestic cats remain concerning, and there have been a few relevant new developments on the issue.
The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service—the office that is monitoring the avian influenza outbreak in domestic and wild animals—has not announced any new detections of bird flu in mammals since March began. Several local officials have recently announced new cases in pet cats, however. The reports include two cats in Kansas without specified potential exposure routes, outdoor cats in New Jersey, cats that drank raw milk in Los Angeles and cats that ate raw food in Washington State and Oregon.
In conjunction with the cases in Washington State and Oregon cases, on March 1 a Washington-based company called Wild Coast Raw voluntarily recalled some of its raw cat food after the H5N1 virus was found in the product. This was at least the third instance in which raw pet food was connected to infected pet cats in recent months. Experts have encouraged people to protect pet cats from bird flu by keeping them inside and not feeding them raw food or milk.
According to the U.S. Centers for Disease Control and Prevention, bird flu symptoms in pets include fever, fatigue, poor appetite, red or inflamed eyes, discharge from the nose or eyes, trouble breathing and neurological effects, including tremors and blindness.
New Research on the Virus
Scientists recently released two new interesting findings about avian influenza genetics and transmission potential.
The first was reported in a paper published in Emerging Microbes & Infections that analyzed a bird flu strain that infected poultry farms in British Columbia in late 2024. Scientists found that, in this area, the virus that has been killing poultry across North America picked up a mutation from a local, less pathogenic avian influenza virus. This mutation is often found in flu strains that are resistant to oseltamivir, a common influenza treatment for humans that is sold under the brand name Tamiflu. The mutation detection raises concerns that if the strain were to spread more widely and infect humans, it would be difficult to mitigate.
The second finding was described in a preprint paper that is currently awaiting peer review and publication. In the study, researchers confirmed that pigs can be infected by the avian influenza virus strain that is circulating most prevalently in U.S. dairy cattle. That’s concerning because pigs are a key species for influenza transmission; they are vulnerable to infection by both avian and human varieties of flu. If the same pig was infected by both avian and human types of flu virus, the viruses could intermix, creating a new, dangerous avian influenza strain that could be better equipped to infect humans.
Bird Feeder Questions
Generally, experts advise caution around dead wild birds. But with high levels of avian influenza circulating in wildlife, we wondered whether bird feeders could be dangerous for wild animals or a source of exposure for humans. In 2022, the U.S. Department of Agriculture recommended that people who keep poultry remove feeders, but additional guidance has been scarce. Krysten Schuler, a wildlife disease ecologist at Cornell University, says that, assuming you don’t keep poultry, you probably don’t need to take down your feeders because avian influenza doesn’t affect all species equally.
Birds that visit feeders tend to be small perching ones that are scientifically known as passerines. “We haven’t seen a lot of [highly pathogenic avian influenza] in passerines that you would encounter at a bird feeder,” Schuler says. She recommends sticking with her usual maintenance advice: clean the feeder every two weeks or so to prevent a range of infections and call the state wildlife management agency to report dead wild birds.