Bird Flu in Humans and Animals: H5N1 Risk Explained

Bird Flu in Humans and Animals: H5N1 Risk Explained

H5N1 bird flu is spreading among wild birds, poultry, dairy cows and other mammals, and it has infected a small number of people, mostly farm workers with close animal contact. The US Centers for Disease Control and Prevention (CDC) says the current risk to the general public is low. The main things you can do are avoid sick or dead animals and skip raw milk.

This article is for anyone who has seen the headlines and wants to understand what has changed, who is actually at risk, and what sensible precautions look like.

Key takeaways

  • H5N1 now infects a much wider range of animals than before, including US dairy cattle since 2024.
  • Most human cases have followed unprotected contact with infected cows, poultry or wild birds. Most US cases have been mild, with eye redness the most common symptom.
  • There's no sustained person-to-person spread so far. That is the key signal health agencies are watching.
  • Pasteurized milk is safe. Raw milk and raw milk products can carry the virus.
  • If you get flu-like symptoms or red, irritated eyes within about 10 days of animal exposure, call a doctor and mention the exposure. Antivirals work best when started early.

What is bird flu, and why does H5N1 get so much attention?

Bird flu, or avian influenza, is a group of flu viruses that mainly circulate in birds. Flu viruses are named after two proteins on their surface, hemagglutinin (H) and neuraminidase (N), which is where names like H5N1 come from. Many subtypes exist, and most rarely affect people.

H5N1 stands out for three reasons. It spreads easily among birds. It can infect mammals, including humans. And historically, a high share of the human cases reported worldwide were severe or fatal. That figure likely overstates the true risk, because mild infections often went untested, but it explains why health agencies take H5N1 seriously.

The virus has changed over decades of circulating in birds. One branch, called clade 2.3.4.4b, spread around the world from about 2020 onward and has proved able to infect far more kinds of mammals than earlier versions.

Why does spread to mammals matter?

For most of its history, H5N1 stayed in birds and only occasionally jumped to people who handled sick poultry. Recently that pattern changed. The virus has been found in foxes, skunks, bears, mountain lions, seals, sea lions and other wild mammals, with large die-offs in some marine mammal colonies. In March 2024, the CDC reported a multi-state outbreak in US dairy cows, an animal not previously thought to be a major host for bird flu.

This matters because a flu pandemic happens when an animal virus becomes good at spreading between people. To do that, a bird virus has to adapt to human airways, which differ from bird airways in the receptors the virus attaches to and in temperature. Every time H5N1 infects a mammal, it gets more chances to pick up changes that could help it adapt. More infected mammals, especially ones in close daily contact with people like dairy cattle, means more chances.

It's worth being clear about what hasn't happened. The virus has not shown that it can spread efficiently and repeatedly from person to person.

Who is getting infected, and how?

According to the CDC, many US human cases involved unprotected contact at work with infected or sick dairy cows or poultry. Some involved backyard poultry or wild birds, and in some cases the source wasn't identified. Most US cases have been clinically mild. There have been a few hospitalizations and one reported US death.

The people at highest risk are those who handle animals or their products up close:

  • Dairy and poultry farm workers
  • Workers involved in culling or cleaning infected premises
  • Veterinarians and animal health staff
  • Wildlife workers and rehabilitators
  • Backyard flock owners
  • Hunters who handle wild birds
  • People who drink raw milk from affected areas

Walking past ducks in a park, or seeing birds in your garden, has not been shown to spread H5N1 to people. Clusters in households have mostly been explained by shared animal exposure rather than one person infecting another.

Which animals can be affected?

GroupExamplesWhy it matters for people
Wild birdsDucks, geese, gulls, birds of preyMain natural reservoir; spreads the virus along migration routes
PoultryChickens, turkeys, backyard flocksClose contact for farm workers and flock owners
Dairy cattleMilking cowsHigh virus levels in milk; workplace exposure in milking parlors
Wild mammalsFoxes, skunks, bears, seals, sea lionsSignals wider adaptation to mammals
CatsFarm cats, some pets fed raw food or raw milkSevere illness in cats; possible household exposure
PigsFarmed pigsCan carry both human and bird flu, allowing genes to mix

Pigs get special attention because they can be infected with human and bird flu viruses at the same time, letting the viruses swap genes. That kind of mixing helped produce the 2009 H1N1 pandemic virus.

Is milk safe to drink during the outbreak?

Pasteurized milk is. The CDC says pasteurization kills the virus, and the US Food and Drug Administration (FDA) notes that pasteurization effectively kills raw milk pathogens without meaningfully reducing milk's nutritional value.

Raw milk is a different story. Infected cows shed large amounts of virus in their milk, and cats on affected farms that drank raw milk became severely ill. The CDC advises not touching or drinking raw milk or raw milk products, especially from animals that are infected or suspected to be, or from herds in areas with known outbreaks. If you're curious how dairy fits into a healthy diet more broadly, see the truth about dairy nutrition.

Properly cooked poultry and eggs are safe too. Cooking to the recommended internal temperature kills flu viruses along with other germs.

Don't forget pets. Avoid feeding cats or dogs raw milk or raw pet food made from poultry, and keep cats away from dead birds where you can.

What are the symptoms of bird flu in people?

The CDC lists eye redness and irritation (conjunctivitis) as the most common symptom among recent US cases. Other symptoms include:

  • Fever (100°F / 37.8°C or higher), though fever may be absent
  • Cough, sore throat, runny or stuffy nose
  • Body aches, headache and fatigue
  • Less often, diarrhea, nausea or vomiting

More severe illness can bring shortness of breath, high fever, confusion or seizures, and complications such as pneumonia and respiratory failure. Respiratory symptoms typically start about three days after infection, with a range of roughly two to seven days. Eye symptoms can appear one to two days after exposure.

Because these symptoms look like ordinary flu or a cold, the key clue is exposure. If you've been near sick or dead birds, infected cattle or raw milk in the past 10 days and you feel unwell, tell your doctor about that contact so they can arrange testing.

How is bird flu treated, and is there a vaccine?

Flu antivirals called neuraminidase inhibitors, including oseltamivir, work against current H5N1 strains and are most effective when started as early as possible after symptoms begin. They are also sometimes given to people after a high-risk exposure. Severe cases may need hospital care, including oxygen or a ventilator.

Several H5N1 vaccines have been developed and some are held in national stockpiles for an emergency. Manufacturers have been updating candidates to better match the strains now circulating, including with mRNA technology that can be adjusted relatively quickly. Health authorities haven't recommended H5N1 vaccines for the general public, because the virus isn't spreading between people. That advice would change quickly if the situation did.

Seasonal flu vaccines don't protect against H5N1. The CDC still recommends them for farm workers with animal exposure, because avoiding seasonal flu reduces the chance of being infected with both viruses at once, which is one way new strains could arise.

How can you protect yourself?

For most people

  1. Don't touch sick or dead birds or other wild animals. Watch from a distance.
  2. Report sick or dead wild birds or animals to your state wildlife agency or veterinarian rather than handling them.
  3. Choose pasteurized milk and dairy products.
  4. Cook poultry and eggs thoroughly and wash hands after handling raw meat.
  5. Keep pets away from dead birds and don't feed them raw milk.
  6. Get your information from public health agencies rather than social media. Our piece on how fake health news spreads explains why that matters during outbreaks.

For workers and flock owners

  1. Wear the personal protective equipment your employer or health department recommends during close contact: typically a fitted respirator, eye protection, gloves and protective clothing.
  2. Don't eat, drink or touch your face while handling animals, milk or carcasses.
  3. Get a seasonal flu vaccine each year.
  4. If you get sick within 10 days of exposure, the CDC advises staying home and notifying your local or state health department, and seeing a doctor promptly.
  5. Hunters should not handle birds that are obviously sick or found dead, and should not eat or drink while cleaning game.

How worried should you be? A practical risk guide

Headlines rarely separate the farm worker from the city commuter. Here's a rough way to place yourself, based on current CDC guidance:

Your situationRelative riskWhat makes sense
City or suburban resident with no animal contactLowNormal food hygiene, pasteurized dairy, stay informed
Bird feeder in the garden, or walks near pondsLowDon't handle sick or dead birds; clean feeders with gloves
Pet cat that goes outdoorsLow for you, higher for the catNo raw milk or raw poultry pet food; call a vet if the cat becomes suddenly ill
Backyard chickens or ducksModerateKeep flocks away from wild birds, wear gloves to clean coops, report sudden deaths
Raw milk drinkerModerate to high during outbreaksSwitch to pasteurized products
Dairy, poultry or culling workerHighestFull protective equipment, seasonal flu vaccine, report symptoms quickly

A common mistake is worrying about the wrong things: avoiding parks or cancelling travel while still buying raw milk, or letting children pick up a dead bird to "have a look". The precautions that matter are specific and simple.

Backyard flock owners deserve a bit more detail, because they sit between farm workers and the general public. Signs of bird flu in chickens include sudden death without warning, swollen heads or combs, purple discoloration, a sharp drop in egg laying, and breathing trouble. If several birds sicken or die quickly, don't handle them barehanded. Contact your state veterinarian or agriculture department, who can arrange testing. Keep feed and water covered so wild birds can't reach them, and use dedicated shoes or boot covers for the coop.

What would signal a bigger threat?

Public health agencies are watching for a few specific warning signs:

  • Human cases with no animal exposure, suggesting spread in the community.
  • Clear chains of person-to-person spread.
  • Genetic changes in the virus known to help it attach to human airways or spread through the air.
  • A rise in severe cases or rapid geographic spread among people.

Countries already have plans for that scenario: stockpiled antivirals, vaccine production that can be scaled up, and international reporting rules. Other outbreak stories on this site, such as our coverage of the Uganda Ebola outbreak and CDC travel advice, show how those systems work in practice.

H5N1 has been known since the 1990s and hasn't caused a pandemic in that time, which is a reason for some humility in both directions. It may never adapt to people. But the virus is in more species and more places than before, and there's ongoing human exposure through farm work. The sensible stance is steady attention, not panic and not dismissal.

FAQ

Can you catch bird flu from eating chicken or eggs?

Properly handled and cooked poultry and eggs are considered safe. Cooking to the recommended internal temperature kills flu viruses, and infected flocks are removed from the food supply. The bigger practical risk is handling raw poultry and then touching your face, so wash hands, utensils and surfaces afterward, as you would to prevent other food poisoning.

Can bird flu spread from person to person?

Not in any sustained way so far. Most human cases have come from direct contact with infected animals, and household clusters have generally been traced to the same animal source. Health agencies watch closely for any sign of ongoing spread between people, because that would be the main step toward a pandemic. The CDC rates the current risk to the general public as low.

What should I do if I find a dead bird in my garden?

Don't touch it with bare hands, and keep children and pets away. Many areas ask you to report dead wild birds to your state wildlife agency or veterinarian. If you're told to dispose of it yourself, wear gloves or use an inside-out plastic bag, double-bag it, and wash your hands well. Watch for eye redness or flu symptoms over the next 10 days.

What to do next

  • Switch to pasteurized milk and dairy if you currently buy raw products.
  • If you work with animals, check that you have the right protective equipment and know who to call if you get sick.
  • Save your state or local health department's website and the CDC bird flu page for reliable updates.
  • If you develop red eyes or flu-like symptoms after animal exposure, call your doctor promptly and mention the contact.

This article is for general information and is not medical advice. Situations change quickly during outbreaks, so check current guidance from your local health department. See a doctor promptly if you develop eye redness, fever or breathing symptoms after contact with birds, livestock or raw milk, and seek emergency care for shortness of breath, confusion or seizures.

Sources

Last reviewed: October 2026.

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