Bird flu has caused growing problems for the last year. Here's what we know so far.
Since arriving on a Texas dairy farm nearly a year ago, bird flu has caused havoc in the farming industry, leading to millions of dead birds and thousands of sick cows. More than 65 people have also been infected, including one Louisiana resident who died. And America is facing unprecedented egg shortages and skyrocketing grocery prices, as worries about the risks to people mount.
Bird flu, also known as H5N1, is a variant of the influenza virus that sickens tens of millions of people every winter. But because it has not previously infected humans, we have not built up immunity against it, so it is believed to be more dangerous.
In other parts of the world, where it has been circulating since 1997, bird flu has killed roughly half the people known to be infected, though it's possible that more contracted the virus and didn't know it.
Here's a summary of what's currently known about bird flu and what you can do about it.
What is bird flu?
Bird flu is a variation of the influenza virus that humans alive today have not been exposed to before and therefore have not built up immunity against. The flu virus mutates constantly, which is why people need flu shots every year and some years the shots are more effective than others.
Technically called "highly pathogenic avian influenza," bird flu is believed to be extremely dangerous to people because of its novelty and the death rate in other countries in previous years.
So far, it has been difficult for people to catch H5N1. In people, mild cases of bird flu cause symptoms similar to those of the seasonal flu, such as fever, runny nose, body aches and fatigue, as well as conjunctivitis ‒ a type of eye infection.
But with a few simple mutations, it could become easier for humans to get it and pass it around, like COVID-19, said microbiologist Marcy Peteroy-Kelly, dean of Manhattan University’s Kakos School of Arts and Sciences.
In and around New York City, the goal of closing live bird markets for a week is meant to slow the spread of bird flu in poultry populations, to decrease the opportunities the virus has to mutate in different species. Animals in live markets are often in crowded conditions, perfect breeding grounds for such changes.
“When that happens, that’s what leads to a pandemic,” Peteroy-Kelly told Paste BN.
Who is most at risk for severe illness from bird flu?
Severe cases of bird flu could occur more often, especially as the virus continues to spread and evolve.
The Louisiana resident who died of the infection was 65 years old and had other complicating health conditions, while the sickened farmworkers were younger, had mild symptoms and recovered.
It may be then, that older people with health issues will be at higher risk from bird flu ‒ but that's not known for certain because the virus can change. In the 1918 flu outbreak, which killed as many as 50 million people worldwide, it was young adults who were most likely to die because older people were exposed to related flu viruses earlier in their lives.
The Centers for Disease Control and Prevention still considers the general population at "low" risk for catching bird flu.
Workers who interact with sick animals remain at highest risk and should wear protective gear at all times when around the animals, the CDC says.
Can wild animals get bird flu?
Bird flu is called that because it was first seen in wild birds in the late 1990s, and is apparently spread as these birds migrate. Just in the first 17 days of this year, 21 states reported bird flu in wild birds, according to the U.S. Department of Agriculture.
In the last few years, perhaps after an adaptive mutation, bird flu has jumped to a wide number of mammal species, including seals, bears, skunks, foxes, cougars, bobcats, dolphins and even a polar bear.
The Louisiana resident who contracted bird flu and died apparently caught it from a backyard flock.
Can farm animals get bird flu?
Farm animals also interact with wild birds.
Cows on a dairy farm in Texas were apparently infected by wild birds some time in late 2023 or early 2024, which is how the current outbreak in U.S. dairy farms began.
Infected dairy cows produce far less milk while sick. Although they typically recover from the virus, their production may remain low, which has been a financial hit to dairy farms in the 16 states hit by the virus.
Bird flu led to the deaths of nearly 50 million domestic birds in 2024 and more than 19 million already this year, according to USDA. Any poultry farm where the virus is detected must put all its animals to death to prevent spread of the virus. Unfortunately, that process is labor-intensive and extremely unpleasant, and a number of the people infected caught the virus while culling chickens.
The same variant of bird flu that infected the Louisiana resident and a Canadian teenager was just identified in Nevada dairy herds. All previous herds had been infected with a different variant, which might explain why it caused less severe illness in the farmworkers.
Can cats get bird flu?
Cats can get bird flu, and half known to be infected died, according to a study from last summer on farm cats fed raw milk from infected cows.
Cats have also been infected by eating pet food contaminated with the virus.
It's not clear whether cats have infected people or vice versa, but a story in The New York Times Thursday suggests such infections have occurred.
What can you do to protect yourself from bird flu?
The general public should avoid touching wild birds and should consider keeping cats indoors, according to the American Veterinary Association.
Eggs and chicken meat are considered safe to eat, as the U.S. Department of Agriculture regularly checks farms for bird flu and chickens are put to death if the virus is detected on a farm. In New York State, the governor closed a live poultry market Friday. to reduce the risk of infection.
Beef is also considered safe if cooked to proper temperatures and the commercial milk supply is tested regularly to confirm it is safe, the USDA says.
Federal health officials recommend avoiding raw milk, which has been shown in some cases to contain the virus, though no one has yet been confirmed to have gotten sick by drinking unpasteurized milk.
Are there treatments for bird flu?
The farmworkers identified with bird flu were treated with Tamiflu, used to treat the seasonal flu, which seemed to help, suggesting that it can be useful against bird flu.
The U.S. government has also prepared doses of vaccine that it believes will protect against this flu strain, though it has not used them yet because the cases were mild and there was no evidence of person-to-person transmission.
It is also unclear whether the virus will mutate so much by the time it becomes a larger threat to people that the vaccine and treatment will no longer be effective.
Contributed: Eduardo Cuevas
(This story has been updated to add new information.)