How Does Bird Flu Spread to Humans?

The recent outbreak of bird flu virus among dairy cows in the United States has sparked concerns about the potential transmission of the virus to humans. 

Bird flu, also known as avian flu, is an infectious viral illness caused by various strains of the influenza virus. It primarily affects bird populations but has impacted other animals as well; since 2022, bird flu caused by the H5N1 influenza strain has affected over 90 million chickens, 9,000 wild birds, and 36 dairy herds, according to the Centers for Disease Control and Prevention (CDC).

With a growing number of birds and animals becoming infected, is it possible that more human transmission is next? That’s not likely, experts say. Here’s what you need to know.

Can Bird Flu Spread to Humans? 

Bird flu can spread to humans, however, cases of human infection are rare, Linda Yancey, MD, infectious disease specialist at Memorial Hermann Health System in Houston, told Verywell in an email. 

“Bird flu tends not to easily infect humans, but the World Health Organization (WHO) and the CDC are monitoring the situation,” Yancey said.

In the United States, two confirmed human cases of bird flu have been reported. One case occurred in 2022 following exposure to poultry, while the second case was reported in 2024 following exposure to dairy cows. 

“One was in a Colorado poultry worker and the other was working with cattle that had become infected with bird flu,” Yancey said. So far, there have been no reported instances of human-to-human transmission in the country.

How Does Bird Flu Spread to Humans? 

Human cases of bird flu usually happen after close or extended contact with infected birds or environments where sick birds have been present. People can become infected after exposure to a sick bird’s saliva, mucus, or feces, Luis Ostrosky, MD, chief of infectious diseases and epidemiology with UTHealth Houston and Memorial Hermann, told Verywell.

“The transmission we’ve seen has been with farmers who take care of cattle or people who are in contact with birds, chicken coops, etc.,” Ostrosky said.

Human infections can also occur via inhalation if the virus gets into your eyes, nose, or mouth, according to the CDC. It’s also possible to get bird flu if you touch something with the virus on it and then touch your mouth, eyes, or nose.

While human infections with bird flu have occurred through an intermediary animal, such as a cat or a cow, this has only happened on extremely rare occasions. The spread of bird flu from one infected person to a close contact is also very rare. Even in cases where it has happened, it has not led to continued spread among people.

Given that the virus can be present in chicken and cows, there’s a potential—albeit unlikely potential—for exposure to bird flu through raw milk or eggs, Dele Ogunseitan, PhD, MPH, distinguished professor and University of California Presidential Chair, told Verywell in an email. 

“It’s not responsible to say absolutely that bird flu cannot be transmitted through food,” Ogunseitan said. “All foods from bird sources should be cooked properly.” 

However, experts suggest that the likelihood of humans contracting the virus from consuming, meat, dairy, or eggs is low. “It’s unlikely to be transmitted by ingestion directly of food but more so related to touching contaminated eggs, for example,” Ostrosky said.

According to the United States Department of Agriculture (USDA), properly prepared and cooked poultry, and eggs do not pose a risk of transmitting bird flu. There is also no evidence to suggest that humans can get bird flu by consuming food that has been cooked and pasteurized, says the Food and Drug Administration (FDA).

What Types of Animals Can Spread Bird Flu? 

Bird flu normally infects and spreads among birds, such as domestic poultry like chickens and turkeys and wild birds like ducks and geese, said Yancey. These birds can carry and spread the virus through their respiratory secretions, feces, saliva, and contaminated surfaces. 

“Any type of bird can be infected, and they have a high mortality rate,” said Yancey. “Pretty much all wild and domestic birds are at risk: chickens, pigeons, pet parakeets, etc.” 

Aside from birds, animals such as pigs, horses, dogs, and bats can become infected with and spread bird flu.

Who Is At Risk of Getting Bird Flu? 

Although bird flu viruses typically don’t infect people, rare cases of human infection can still occur. According to Ostrosky, certain individuals are at a higher risk of getting bird flu, including poultry farmers, workers involved in poultry handling or processing, and those who work with poultry products. 

Other groups who may be at risk for bird flu include wildlife conservationists, veterinarians, people who work at bird and other animal sanctuaries or bird rehabilitation centers, and responders to bird flu outbreaks in birds or other animals.

What’s Preventing Bird Flu From Spreading Widely? 

As of right now, the bird flu virus is not expected to spread widely from person to person due to its low rates of human-to-human transmission, Yancey said.

Even if someone were to get bird flu, it’s less likely to spread easily from person to person.

“The virus would need to mutate to form more like a human influenza virus to be a threat to the general public,” said Yancey.

Ostrosky added that viruses make millions of copies of themselves every day and there are errors continuously. However, if one of those mutations or errors becomes successful in making it more transmissible between humans, that’s when we would be worried, he said.

“If [bird flu] were to become more effectively transmitted between humans, it would pretty much create a pandemic again with very little immunity, with massive amounts of people getting sick,” Ostrosky added. However, a bird flu vaccine is both feasible and in the works.

Another factor that’s contributing to the prevention of widespread bird flu transmission is the presence of surveillance systems by health organizations that monitor bird and human populations for signs of bird flu, said Yancey. Having surveillance systems in place allows for early detection and rapid response measures if needed.

“Because this is a known possibility, the CDC and WHO track bird flu cases closely. If it ever becomes a broader problem, we would have plenty of warning,” said Yancey.

For now, Ostrosky said the general public should not be concerned.

“At this point, agricultural workers and veterinarians are the most concerning population, and we just need to watch the situation,” he said.

How to Keep Yourself Safe 

Since human cases of bird flu are rare, the general population primarily needs to stay informed and up-to-date about any developments, including transmission patterns and preventative measures, Ostrosky said.

“All I would recommend is to keep an eye out for more information,” he said. “If we document that it starts transmitting more effectively in human populations, yield to general public health recommendations, which in general for the flu are hand washing and avoiding enclosed spaces.” 

However, if you’re part of a high-risk group, Ostrosky and Ogunseitan said there are some precautions you can take to help minimize the risk of contracting bird flu.

• Wash your hands with soap and water, especially after touching birds. 
• Use protective equipment such as gloves, goggles for eye protection, and a properly fitted mask like a surgical mask or N95 respirator.
• Change your clothes before coming into contact with healthy domestic poultry and after handling infected or potentially infected birds and other animals with bird flu.
• Avoid touching your mouth, nose, or eyes after contact with birds or surfaces and materials that may be contaminated with saliva, mucous, or feces from wild or domestic birds. 
• Keep away from touching dead birds or animals.
• Call your local public health agency or animal control if you come across a carcass or sick wild animal/bird.