Health Basics: Bird Flu
Learn key facts about symptoms, how it spreads, and how it can be prevented.
Reviewed by Gino Lorenzoni, DVM, MS, PHD, and Stephen Ostroff, MD. Last updated June 16, 2025.
Bird flu is a highly contagious virus that primarily affects wild birds and poultry. The virus can infect other animals, such as domestic and wild mammals. In the United States, there are current bird flu outbreaks widely affecting domestic poultry and dairy cattle. In rare cases, people have become infected with bird flu. Although human-to-human transmission has not been documented in the United States , public health scientists are concerned that, if outbreaks continue, the virus could evolve, begin to spread among people and pose a pandemic risk.
What is bird flu?
Bird flu is caused by avian influenza A viruses that mainly affect birds. Some bird flu viruses , like H5N1, can cause severe disease in birds and are referred to as highly pathogenic avian influenza (HPAI). HPAI viruses can sometimes infect other animals and people. The current outbreak of bird flu in the United States is caused by the H5N1 virus.
Domestic poultry, like chickens, are especially vulnerable to the virus and often develop severe infections. Photo: Stephen Ausmus (USDA Agricultural Research Service)
How is it different from regular flu?
Although both are caused by influenza viruses, bird flu and seasonal flu are different. Seasonal flu viruses regularly spread among people every year. So far, there is no evidence that HPAI viruses readily spread among humans.
How does bird flu spread among animals?
Bird flu can affect many different types of wild birds (especially waterfowl like ducks and geese) and domesticated birds, including chickens and turkeys. It is highly contagious among birds. In some birds the virus can cause no symptoms while in others it can lead to fatal infection. Spread occurs through contact with saliva, nasal secretions, or droppings of infected birds.
Domestic poultry are especially vulnerable to the virus and often develop severe infections. When flocks become infected, entire groups often must be euthanized to prevent further spread, which can lead to shortages and rising prices for eggs and poultry products.
In some cases, bird flu has infected animals like cows and other mammals. In March 2024, the first known outbreak of bird flu in dairy cows was recognized in several US states.
Infection is uncommon, but cats can contract bird flu and develop severe disease. Exposure can be limited by keeping cats indoors and away from wild birds and not feeding cats raw pet food or unpasteurized (raw) milk.
Can people catch bird flu?
Although rare, people can become infected with bird flu. This usually happens through close contact with infected animals or contaminated environments. People who work with poultry or dairy cattle face the highest risk. Since 2022, 70 confirmed cases of bird flu have been reported in people in the United States: 41 of these infections occurred among dairy farm workers, 24 through poultry operations, 2 through exposure to other infected animals, and, in 3 cases, the exposure source is unknown.
Why are public health officials concerned about bird flu?
Bird flu is a zoonotic disease, meaning it can jump from animals to humans, which carries pandemic potential.
While most human cases have been linked to close contact with infected birds or animals, the virus is constantly evolving, and public health scientists are concerned it could eventually spread efficiently between people.
The bird flu has already spread to new species, such as pet cats, wild mammals, and dairy cattle. This raises concern about the virus adapting to infect humans more easily through human-to-human transmission.
If the virus were to adapt to spread efficiently between people, it could cause a serious global health emergency, with potential for severe disease and death.
Ongoing monitoring and surveillance in animals are crucial to catching any changes early and preventing a broader outbreak.
Dairy cows graze in a field. In March 2024, the first known outbreak of bird flu in dairy cows was recognized in several US states. Photo: Wayne Coblentz (USDA Agricultural Research Service)
What are the symptoms of bird flu in humans?
Symptoms of bird flu in people can range from mild, such as eye infections or flu-like symptoms, to severe symptoms like acute respiratory infections. In rare cases, bird flu can even cause death. In the US, most cases of bird flu have been mild. However, in January 2025, Louisiana reported the first bird flu-related death in the United States after exposure through backyard chickens and wild birds.
Common signs of bird flu infection in people include fever, cough, sore throat, muscle aches, and sometimes shortness of breath. Gastrological and neurological symptoms have been reported in rare cases.
How is bird flu diagnosed and treated?
To diagnose bird flu in a person, health care providers use samples of nasal or throat fluid to test for infection. Specific tests are needed to distinguish bird flu infection from seasonal flu. Treatment with antiviral medicines is recommended and treatment is most effective when started as soon as symptoms begin.
Is there a vaccine for bird flu?
There have been efforts to develop vaccines to prevent bird flu among people. Since 2007, the United States has licensed three vaccines to prevent H5N1. The European Medical Association has also authorized vaccines. The vaccines are not intended for the general public, but rather for individuals who have a high risk of exposure, such as poultry workers; however, these vaccines have not yet been used among these populations in the United States. Several countries, including the United States, have stockpiles of these vaccines. Components to manufacture bird flu vaccines are also stockpiled.
There is currently no effort to develop a bird flu vaccine for the public in the United States.
Vaccines have also been tested for use in animals at risk of contracting bird flu, including an experimental vaccine that was found to be protective in research mice. In February 2025, a vaccine to protect poultry from infection was conditionally approved in the United States. Several countries, including China and Mexico, immunize poultry against bird flu.
Is it safe to eat chicken and eggs? Is it safe to feed wild birds?
Yes, properly cooked poultry and eggs are safe to eat. Bird flu and other viruses are killed by cooking poultry and eggs to an internal temperature of 165°F. Testing has even shown that beef containing the H5N1 virus is safe to eat when cooked to temperatures of 145°F and above. Pasteurized milk is safe as the pasteurization process kills avian influenza viruses along with other viruses and bacteria. Avoid eating raw or undercooked poultry or eggs and avoid consuming raw milk.
In most cases, it is safe to feed wild birds because songbirds are currently classified as having a low risk of contracting bird flu. Although waterfowl like geese easily contract and transmit bird flu among one another, there are few cases of songbirds getting bird flu.
In general, anyone feeding wild birds should wash their hands thoroughly after touching bird food, feeders, or other areas in contact with wild birds. Bird feeders and bird baths should be cleaned to reduce disease risk.
Can pets like backyard chickens or pet birds get bird flu?
Yes, backyard chickens and other domestic poultry can become infected, especially during times when there are outbreaks in wild birds or poultry. In addition to practicing good hygiene like washing hands, keeping poultry living areas clean, and avoiding contact with sick birds, people who keep backyard chickens should avoid contact between the chickens and wild birds. Owners should also monitor their animals to identify signs of bird flu as early as possible. Symptoms include tremors, twisted neck, and paralyzed wings, among others.
Pet birds kept indoors with no contact with wild birds are unlikely to become infected with bird flu.
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Disclaimer: The information provided on this website is for informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health care provider with any questions you may have regarding a medical condition.
