What Is Bird Flu?
Bird flu, also called avian influenza, is a viral infection that can cause flu in birds and sometimes spread to mammals, including humans. Migrating waterfowl (wild ducks, geese, and storks) are natural carriers of bird flu viruses. Scientists suspect that infection can spread from wildfowl to domestic poultry (chickens and turkeys) and some mammals.
Bird flu is mostly a threat to birds and doesn’t spread easily among people. But a 2024 outbreak affected dairy cows and people who work in the dairy and poultry industries in the United States.
There have been very few cases of human-to-human transmission during bird flu outbreaks. The rare instances were among people with very close contact, such as a mother who caught the virus while caring for her sick infant. No person-to-person spread has been reported in the 2024 outbreak.
The most common kind of bird flu is the H5N1 strain.
Has bird flu been seen in the United States?
Various strains of bird flu pop up in U.S. poultry from time to time. When they do, farmers cull (remove and kill) all affected poultry flocks.
For example, in 2004, a highly dangerous bird flu strain appeared in a Texas chicken flock. The outbreak involved an H5N2 virus (not the H5N1 bird flu). By April 2004, the outbreak had ended. No human infections were detected.
The CDC considers bird flu “widespread” in wild birds and “sporadic” in poultry. They estimate more than 125 million birds are affected with bird flu in the U.S.
Bird flu 2024
The latest U.S. outbreak started in 2022. As of December 2024, it had affected nearly 11,000 wild birds and 125 million poultry. All 50 states had poultry outbreaks.
In March 2024, the virus was detected for the first time in dairy cows. According to the CDC, H5N1 bird flu has infected 876 dairy herds in 16 states. As of December 2024, there were 65 confirmed cases of bird flu in humans in the United States. Most of the cases were in California, Colorado, and Washington state.
The CDC still considers the risk of getting H5N1 very low for humans. All of the cases have been from direct contact with poultry or cows that had the virus. There has been no person-to-person spread of the virus.
Bird Flu Symptoms
Symptoms of bird flu show up differently in birds and in humans. Sometimes birds with bird flu show no signs of the virus before dying suddenly. Humans tend to have upper respiratory or lung symptoms but can have symptoms in other parts of the body, too.
Symptoms of bird flu in birds
Birds with the virus may have symptoms such as:
- Low energy
- Low appetite
- Purple discoloration or swelling of various body parts
- Laying fewer eggs
- Soft-shelled or misshapen eggs
- Nasal discharge, coughing, sneezing
- Lack of coordination
- Diarrhea
In chickens, bird flu may involve:
- Signs of depression in egg-laying chickens
- Ruffled feathers
- Being quieter than normal
- Purple or dry combs
If you suspect a bird or other animal is infected with bird flu, don't touch the bird, their poop, or any water source that may have come into contact with their saliva, poop, or other body fluids. Notify a veterinarian or call the United States Department of Agriculture (USDA) at 866-536-7593.
Bird flu in humans
Bird flu symptoms in people can vary. The illness often comes on quickly and may start out with mild flu-like symptoms that include:
- Fever (100 F or higher)
- Muscle aches
- Headache
- Cough
- Sore throat
- Tiredness
- Runny or stuffed nose
- Red or pink and irritated eyes
In some people, the symptoms may continue or get worse, and include:
- High fever
- Nausea
- Diarrhea
- Vomiting
- Shortness of breath or trouble breathing
- Changes in thinking or mental status
- Extreme tiredness
- Seizures
The virus mainly affects the respiratory tract – the nose, mouth, throat and lungs. But there have been a couple of cases in which the virus infected the brain and digestive tract in humans, which can be life-threatening. These cases show that bird flu in humans may not always look like the typical flu.
Bird flu and pets
It’s possible – but unlikely – for pets such as cats and dogs to get infected with bird flu. They may get it if they eat a dead bird that has the virus. Rarely, bird flu in cats can happen if cats drink unpasteurized milk or eat undercooked or raw meat from a cow that's infected with the virus.
Overall, the chances of cats and dogs getting bird flu is very low.
There haven’t been a lot of studies on how bird flu shows up in pets, but if your pet is infected, you may see these symptoms:
- Fever
- Sluggishness
- Lack of appetite
- Red or swollen eyes
- Weeping from the eyes and nose
- Breathing problems
- Problems with balance and coordination
- Vision problems
- Seizures
- Shaking
Some of these symptoms are the same as those seen in other respiratory illnesses that dogs and cats can get. If your pet shows these signs, take them to your veterinarian right away for a diagnosis.
Bird Flu Causes
Bird flu is caused by influenza A viruses.
How does bird flu spread to humans?
People catch bird flu by close contact with an animal’s fluids, such as saliva, respiratory droplets, or droppings (poop). You may breathe in small dust particles containing the virus in the animal’s habitat, or transmit it by touching your eyes, nose, or mouth after you touch an animal’s bodily fluids.
In the 2014 outbreak, some people caught H5N1 from cleaning or plucking infected birds. There were reports in China of infection by breathing in viral particles in live bird markets. It's also possible that some people were infected after swimming or bathing in water contaminated with the droppings of infected birds. And some infections have occurred in people who handle fighting cocks.
People don't catch the virus from eating fully cooked chicken or eggs. But your risk of catching the virus is slightly higher if you:
- Work with poultry or cattle
- Travel to countries with bird flu
- Come into contact with sick or dead animals infected with the virus
- Are exposed to animal droppings, litter, or other material contaminated by animals infected with H5N1
- Eat raw or undercooked poultry meat, eggs, or unpasteurized (raw) milk or cheese from animals infected with H5N1
There have been a few cases where one infected person caught the bird flu virus from another person, but only after close personal contact.
In Indonesia in 2006, eight members of the same family were infected with bird flu. Seven of them died. It's not clear exactly how this happened. Family members likely had similar contacts with infected birds. They may also have shared genes that made them very likely to get the virus. But casual contact does not seem to have been involved.
Bird flu virus in cow’s milk
After scientists found H5N1 in dairy cows in March 2024, the FDA started testing retail milk and other milk products for the virus. These studies confirmed that pasteurizing (heating for a short period of time to kill bacteria) milk kills the H5N1 virus.
But milk and milk products that haven’t gone through the pasteurization process are at a higher risk of having the virus. Raw milk is sold legally in many states, but the CDC warns that it's not safe for people to drink.
At least four cases of bird flu in humans in the U.S. are linked to the dairy cow outbreak. All of the people infected were workers on dairy farms. Though H5N1 has been found in raw milk, no confirmed cases in humans have been linked to drinking milk. In December 2024, California health officials investigated a case where a child got sick with influenza A after drinking raw milk. The officials couldn't confirm whether the virus was the bird flu, seasonal flu, or another virus.
Types of Bird Flu
The bird flu virus is divided into two main categories:
Highly pathogenic avian influenza (HPAI)
This type of bird flu causes more serious illness in chickens and is more likely to kill them. H5N1, the most common strain of bird flu, is an HPAI.
Low pathogenicity avian influenza (LPAI)
This type causes less serious illness in chickens and is less likely to cause death. Typically, LPAI causes either no signs or mild signs of disease in birds. Most cases of bird flu are LPAI. In poultry, some low-pathogenic viruses can mutate, or change, into highly pathogenic (disease-causing) avian influenza viruses.
Both versions can spread quickly through bird flocks and may cause serious illness in humans. This is important because birds infected with LPAI viruses may show little or no sign of disease before passing the disease to other animals or humans.
Bird Flu Strains
Viruses often change over time. This leads to different subtypes called strains. Scientists have identified more than a dozen strains, or variants, of bird flu. Researchers know of six subtypes of avian influenza A viruses that have caused human infections:
H3 strains. This subtype affects many water birds around the world. In birds it causes mild or no illness, but it can spread to other species, including humans. The H3 strain in humans was first reported in China in 2022, and it has infected a small number of people.
H5 strains. Most H5 viruses in wild birds and poultry are LPAI, but researchers have identified some HPAI H5 viruses, such as H5N1. H5N1 is one of the deadliest strains for humans. It has caused 939 infections and 464 deaths from bird flu since 2003, according to the World Health Organization.
H6 strains. These strains are typically LPAI types. The first human H6 strain infection was in Taiwan in 2013.
H7 strains. Human H7 infections have been reported in the United Kingdom, the U.S., China, and other Asian countries. While H7N9 infections are uncommon, they have caused severe respiratory illness and death in about 40% of people who are hospitalized with the virus.
H9 strains. The H9N2 strain has mainly affected children and caused mild upper respiratory tract illness. A few infections have led to more severe disease, and death.
H10 strains. Four H10 strains have infected humans: H10N3, H10N5, H10N7, and H10N8. The first case was in Egypt in 2004. A few cases of severe pneumonia and death have been reported in China.
Bird Flu Diagnosis
Doctors can’t diagnose bird flu just by your symptoms. To find out if you have bird flu, your doctor can swab your throat or nose.
Since bird flu isn’t common, you’ll need to tell the doctor if you’ve been exposed to the virus or suspect you could have it. They’ll send your sample to a special lab for testing. Your results are more likely to be accurate if your test happens in the first few days of your illness.
Bird Flu Treatment
If you see a doctor early in your infection, they may be able to prescribe antiviral drugs to help treat your symptoms. These include:
- Oseltamivir (Tamiflu)
- Peramivir (Rapivab)
- Zanamivir (Relenza)
These are drugs you take by mouth. It’s best to take them within 48 hours of having symptoms.
Bird Flu Complications
It’s possible that bird flu may cause further problems once you get it. These include:
- Acute respiratory failure, a life-threatening condition that happens when your body can't provide enough oxygen to your blood and organs
- Organ failure
- Pneumonia
- Sepsis, when your body responds to infection abnormally and begins to attack healthy systems
- Brain swelling
Bird Flu Prevention
Your chances of getting bird flu are very low. But there are steps you can take to help protect yourself from exposure, such as:
- Keep your distance from wild birds, especially birds that seem sick or are dead.
- Stay away from animals you know have the H5N1 virus and any surface they’ve been on.
- Avoid contact with cows infected with bird flu.
- Don’t drink raw milk or eat products made with raw milk. Pasteurized milk is safest.
If you own poultry, you can help prevent the virus with steps such as:
- Keep your flock separate from wild birds.
- Keep your poultry housing area clean.
- Don’t share equipment (such as egg cartons) with others.
Bird flu vaccine
There is a bird flu vaccine, but you can't make an appointment to get it. The FDA approved the first vaccine to prevent human infection with one strain of the bird flu (H5N1) in 2007. But it’s not commercially available to the general public. The U.S. government is developing vaccines against H5N1 in case they're needed.
The seasonal flu vaccine does not protect against bird flu, but it may help prevent a severe infection.
How to Stay Updated on Bird Flu News
The best way to learn more about ongoing outbreak information and statistics is from government agencies such as the CDC and FDA. Local news outlets also cover bird flu news.
Current avian flu map
The CDC publishes a summary of the H5N1 bird flu situation, including a map that shows current infections. The page is updated daily.
Takeaways
Bird flu (avian influenza) is a flu virus that typically affects birds, but in rare cases can spread to other animals and humans. In 2024, the virus appeared in cows, and as of December 2024, there were 65 confirmed cases of bird flu in humans in the United States. Typically, bird flu causes mild respiratory symptoms, but it has caused more severe symptoms and even death.
Bird Flu FAQs
Is a bird flu pandemic possible?
While it’s possible for bird flu to cause a pandemic (a dangerous, worldwide outbreak of illness), it’s unlikely. It can only happen if the virus mutates, or changes so that it’s easier for people to give it to each other and not just get it from birds. That has not happened.
Can bird flu kill humans?
Yes, it is possible for someone with the infection to die from it, but it is rare for humans to get the virus in the first place, and the symptoms can range from almost none to severe.
How deadly is bird flu?
Infections in humans are rare. Some people who get it have little to no symptoms, while for others, it can be severe and cause death.
What happens if a human gets the bird flu?
Your doctor may prescribe antiviral medication if it’s early enough in your infection.
Can you recover from bird flu?
Yes. You may have symptoms for a week or two, but usually they get better over time.
Are there human bird flu cases right now?
As of December 2024, 65 people in the U.S. had been infected with bird flu.
What states have had human bird flu cases?
As of December 2024, 36 people in California, 10 people in Colorado, and 11 people in Washington state had tested positive for bird flu. Iowa, Louisiana, Missouri, Oregon, Texas, and Wisconsin had one case of bird flu each, and Michigan had two cases.
How contagious is bird flu?
Bird flu is highly contagious between birds. It is much harder for humans to catch it.
How fatal is bird flu in humans?
The mortality rate is 50%, meaning half of all people in the world who get bird flu die from it. Very few people get bird flu.
Can you get bird flu from touching a wild bird?
Yes. You should always be cautious and wear protection if you have to handle a wild bird. It’s better to avoid it altogether. A wild bird may have bird flu even if it doesn’t appear sick.
How long does bird flu last?
Typically, mild symptoms last a week or two, but usually they get better over time. Rest and fluids can help you recover.
