Why Bird Flu Is More Than a Bird Problem
A Viral Nesting Ground
Published April 2025
As the name suggests, bird flu circulates among wild birds and poultry farms. However, the virus has jumped to other species, including dairy cows, cats and even people, raising questions about public health. How serious is the risk? And how did a bird virus end up in cows?
— Michael P. Angarone
华体会 Infectious Disease Specialist Michael P. Angarone, DO, explains what we know about bird flu so far.
What Is Bird Flu, and How Does It Spread?
Bird flu, or H5N1 influenza, is a virus that primarily affects avian populations, including wild birds and poultry.
“In birds, it is typically spread by the fecal-oral route, meaning birds become infected by ingestion of infected fecal material,” says Dr. Angarone.
Once exposed, birds often develop respiratory, gastrointestinal and neurologic symptoms, and the chance of survival is low. In commercial poultry farms, where birds are kept in close quarters, bird flu can spread especially quickly.
The virus itself is nothing new; highly pathogenic avian influenza has been endemic in birds across several different countries for years. However, in 2024, bird flu was found in dairy cattle 鈥� a first for the United States. In cows, the virus presents as fever, reduced appetite and a drop in milk production, and likely occurs after a cow grazes on contaminated feed or has contact with infected birds or their droppings.
Bird flu has since been identified in a variety of other mammals, including cats 鈥� who likely contracted it from being exposed to infected cows on dairy farms 鈥� and now, people.
Bird Flu in Humans
Shortly after bird flu was found in dairy cows, the first human case of the virus was identified in the United States. While there is no evidence yet of human-to-human transmission, the virus is nevertheless a concern, with as of April 2025, according to the U.S. Centers for Disease Control (CDC).
According to Dr. Angarone, humans can be exposed to bird flu in several ways:
- Direct contact with infected cows
- Handling birds or dead birds with the virus
- Ingestion of infected animal products, including:
- Undercooked beef or poultry
- Non-pasteurized milk
- Undercooked eggs
When a human contracts bird flu, the one distinguishing symptom is conjunctivitis, or red, itchy eyes. Otherwise, the symptoms of bird flu in humans closely resemble a typical flu. They include:
- Fever
- Cough
- Sore throat
- Body aches
To reduce the risk, it is recommended that you avoid contact with wild or dead birds. You can ensure food safety by fully cooking chicken and other poultry products including eggs, as well as steering clear of raw milk. Pasteurized milk products have been deemed safe to consume.
Why Experts Are Concerned
On a biological level, bird flu is able to jump among species of animals and people because the virus binds its protein, hemagglutinin, to sialic acid proteins in the respiratory tract of mammals. According to Dr. Angarone, this is not necessarily unexpected. What is concerning, however, is the possibility of the virus mixing with a human influenza virus.
“Bird flu could develop pandemic potential if it develops the ability to cause human-to-human spread and infection,” says Dr. Angarone.
The good news is that the current risk of getting bird flu is very low, and the more recent outbreaks in the United States have not been very deadly. For example, in the early 2000s, outbreaks of the virus in Asia had mortality rates between 30% and 35%; meanwhile, the United States has only seen one death from bird flu in 2025 (as of April).
Is Bird Flu Going Away?
Avian flu in mammals is unique in the United States, which is why the CDC is monitoring the situation and working with public health departments to monitor virus activity.
The big issue, Dr. Angarone says, is that the virus is becoming harder to control. Because experts cannot predict which cows are going to get infected, they need to pay attention to where bird flu is spreading and how many people are contracting it.
No bird flu vaccine is available, but efforts are underway to develop one for animals. However, vaccinating birds presents some challenges.
“The difficulty with vaccinating birds is getting all birds vaccinated. The vaccine also does not completely prevent infection in birds,” Dr. Angarone explains. Additionally, a vaccinated bird could still carry the virus but not show signs of illness, which would complicate detection of infected birds.
In short, don’t panic, but play it safe by cooking your food properly and avoiding sick or dead birds. 聽Learn more about bird flu and other travel-related infections.
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