H5N1 Bird Flu: Symptoms, Spread, Treatment and Prevention

Author: Disabled World (DW)
Updated/Revised Date: 2 Nov 2026

Table of Contents:
Synopsis - Definition - About This Section - FAQs - Publications - Subtopics

Synopsis

H5N1 bird flu guide to human symptoms, how avian influenza spreads from birds and dairy cattle, global case counts, antiviral treatment, vaccines and prevention.

At a Glance

• 1 - In 1997, H5N1 outbreaks in Hong Kong poultry led to 18 human infections and six deaths.
• 2 - Eye redness has been the predominant symptom among recent U.S. human cases of H5 bird flu.
• 3 - A Washington backyard flock owner was the first person worldwide confirmed with H5N5 bird flu and died in November 2025.
• 4 - Oseltamivir works best when started within two days of symptoms, although later treatment can still help people who are very ill.

Topic Definition

H5N1 Avian Influenza

H5N1 avian influenza is a highly pathogenic subtype of the influenza A virus that mainly infects wild birds and poultry but can also infect mammals, including dairy cattle, and occasionally people. The name refers to two proteins on the virus surface, hemagglutinin 5 and neuraminidase 1. First identified in farmed geese in southern China in 1996, the virus causes severe, often fatal disease in birds. In humans, infection usually follows close contact with infected animals or contaminated environments and can range from eye redness and mild flu-like symptoms to severe pneumonia and death. It has not shown sustained person-to-person transmission, but health agencies monitor it closely because of its pandemic potential.

Overview

What Is Avian Influenza or Bird Flu?

Avian influenza, known informally as avian flu or bird flu, is illness caused by influenza A viruses that are adapted to birds. The term works the same way as "swine flu" or "human flu" - it describes flu viruses that have adapted to a particular host. Wild waterfowl are the natural reservoir for most of these viruses, and more than 130 combinations of influenza A subtypes have been identified in nature, mainly in wild birds [Centers for Disease Control and Prevention, n.d.-e].

Avian flu viruses are grouped as low pathogenic or highly pathogenic, depending on how severe the disease is in chickens. Highly pathogenic avian influenza (HPAI) spreads quickly through poultry flocks and kills many birds. H5N1 is the HPAI virus of greatest concern. It was first identified in farmed geese in southern China in 1996. In 1997, large outbreaks in Hong Kong poultry led to 18 human infections and six deaths, the first time H5N1 was known to make people seriously ill [Centers for Disease Control and Prevention, n.d.-b].

Since 2020, a variant called clade 2.3.4.4b has killed very large numbers of wild birds and poultry in Africa, Asia and Europe. It reached North America in 2021 and Central and South America in 2022 [World Health Organization, n.d.]. It has also spread to mammals, including marine mammals, dairy cattle and other wild and domestic animals [World Health Organization, 2026].

How Influenza Viruses Are Classified

There are four types of influenza virus: A, B, C and D. Type A is the only type known to cause flu pandemics, and along with type B it causes the seasonal epidemics seen almost every winter. Type C usually causes mild illness, and type D mainly affects cattle and is not known to make people sick [Centers for Disease Control and Prevention, n.d.-e].

Influenza A viruses are divided into subtypes based on two surface proteins, hemagglutinin (H) and neuraminidase (N). There are 18 known H subtypes and 11 known N subtypes, so a name such as H5N1 identifies a virus with hemagglutinin 5 and neuraminidase 1 [Centers for Disease Control and Prevention, n.d.-e].

H5N1, H5N6, H7N9 and Other Avian Flu Viruses in People

Most avian influenza viruses do not infect people. A small number, including A(H5N1) and A(H7N9), have caused serious human infections, and the reported fatality rate for H5 and H7N9 infections has been higher than for seasonal flu [World Health Organization, 2026]. In the Western Pacific Region, H5N6 has caused 93 reported human cases and 58 deaths since 2014. H9N2 has caused 173 cases in the region since 2015, mostly mild, with two deaths [World Health Organization Regional Office for the Western Pacific, 2026].

In late 2025, a backyard flock owner in Washington State became the first person in the world known to be infected with H5N5. The patient was 65 or older, had a history of non-Hodgkin lymphoma, and died after a 28-day illness. Investigators believe wild waterfowl brought the virus into the flock's environment. About 135 people who had contact with the patient were monitored, and none tested positive [Kibiger et al., 2026].

How Bird Flu Differs From Seasonal Flu

Seasonal flu spreads easily from person to person through respiratory droplets and contaminated surfaces. Bird flu does not. Nearly all human cases come from close contact with infected birds or other animals, or with places they have contaminated. The World Health Organization reports that no zoonotic flu virus now circulating has shown sustained human-to-human transmission [World Health Organization, 2026]. The CDC describes human-to-human spread of bird flu as very rare - none has been found in the United States, and only limited spread has occurred in other countries [Centers for Disease Control and Prevention, 2024a].

Severity is the other major difference. Most healthy people recover from seasonal flu, although it can be dangerous for older adults, young children and people with chronic conditions. H5N1 infections range from mild eye or flu-like illness to severe pneumonia and death. Of the 1,000 human H5N1 cases reported to the World Health Organization from 25 countries between January 2003 and July 2026, 479 people died - a case fatality rate of about 48 percent [World Health Organization Regional Office for the Western Pacific, 2026]. That figure reflects severe cases that came to medical attention. Mild or symptom-free infections are less likely to be detected.

Bird Flu in North America

H5N1 is no longer limited to Asia, Europe and the Middle East. In 2024 it spread to dairy cattle in the United States, and some farm workers in contact with infected cows became infected [World Health Organization, 2026]. The USDA continues to confirm infections in dairy herds, including two Washington herds announced in October 2026 [U.S. Department of Agriculture Animal and Plant Health Inspection Service, 2026].

As of October 2026, the CDC has counted 72 human H5 cases in the United States since February 2024. Sporadic cases have occurred among dairy and poultry workers, and the CDC rates the current risk to the general public as low [Centers for Disease Control and Prevention, 2026]. The country's first H5 death was reported in Louisiana in January 2025, in a patient who had been hospitalized with severe illness [Centers for Disease Control and Prevention, 2025a].

In Canada, the Public Health Agency of Canada confirmed the country's first domestically acquired human H5N1 case in November 2024, in a hospitalized teenager in British Columbia. The agency said the risk to the general public remained low, but higher for people with unprotected exposure to infected animals [Public Health Agency of Canada, 2024].

Why Bird Flu Is Concerning

A flu pandemic happens when a virus can spread easily and steadily between people in a population that has little or no immunity to it [World Health Organization, 2026]. H5N1 already meets part of that description - it is new to people and can cause severe illness - but it does not spread easily from person to person. Health experts are concerned that ongoing infections in birds and mammals give the virus more chances to change in ways that could make human spread easier. Whether any current avian flu virus will cause a pandemic is not known [World Health Organization, 2026].

Past pandemics show why surveillance matters. The 1918 pandemic killed at least 50 million people worldwide [Centers for Disease Control and Prevention, n.d.-d]. The 1957 to 1958 H2N2 pandemic caused about 1.1 million deaths [Centers for Disease Control and Prevention, n.d.-a], and the 1968 H3N2 pandemic about 1 million, most of them among people 65 and older [Centers for Disease Control and Prevention, n.d.-c].

How People Become Infected With Bird Flu

Infected birds shed the virus in saliva, nasal secretions and feces. People are most at risk when they have contact with live or dead infected animals, or with contaminated places such as live bird markets. Handling the carcasses of infected birds and preparing infected poultry at home are also risk factors, and farm workers have been infected while culling flocks [World Health Organization, 2026].

The CDC lists the main routes of exposure as contact with sick or dead animals, contaminated surfaces, undercooked poultry or eggs, and unpasteurized milk from infected dairy cows. The virus can also spread through the air in droplets or dust near infected animals [Centers for Disease Control and Prevention, 2024a]. People at higher risk include farm and poultry workers, backyard flock owners, hunters and others with close or long contact with birds or livestock. Older age, underlying medical conditions and delayed medical care may increase the risk of severe illness [Centers for Disease Control and Prevention, 2024a].

Symptoms of Bird Flu in People

Many early symptoms look like seasonal flu, so a person's exposure history is often the key clue. Mild symptoms can include eye redness or irritation, fever of 100 degrees Fahrenheit (37.8 degrees Celsius) or higher, cough, sore throat, a runny or stuffy nose, body aches, headache and fatigue. Fever is not always present, and diarrhea, nausea or vomiting are less common. Eye redness has been the predominant symptom among recent U.S. cases [Centers for Disease Control and Prevention, 2024a].

Moderate to severe illness can bring high fever, shortness of breath or trouble breathing, altered consciousness and seizures [Centers for Disease Control and Prevention, 2024a]. Anyone who develops symptoms within days of contact with sick birds, livestock or raw milk should tell a health care provider about the exposure right away. Trouble breathing, chest pain, confusion, bluish lips or a seizure need emergency care.

Treatment for Bird Flu

Antibiotics do not work against viruses, so they cannot treat bird flu itself, although doctors may use them for a bacterial infection that develops alongside it. The CDC recommends the antiviral oseltamivir (Tamiflu) because it has the most human data supporting its use against bird flu. Outpatients usually take it twice a day for five days. Hospitalized patients may need a longer course, and some may receive combination therapy such as oseltamivir with baloxavir [Centers for Disease Control and Prevention, 2025c].

Treatment works best when started within two days of symptoms beginning, but later treatment can still help people who are very ill or at higher risk of complications. Global data suggest that people treated early had better survival than those treated late or not at all [Centers for Disease Control and Prevention, 2025c]. Treatment decisions should always be made with a doctor.

Vaccines for Bird Flu

Vaccines against H5N1 do exist, but they are not part of routine public vaccination. In the United States, the FDA has approved AUDENZ, an adjuvanted H5N1 vaccine for people 6 months and older who are at increased risk of exposure to the H5N1 strain in the vaccine [U.S. Food and Drug Administration, 2024]. In February 2025, Canada secured 500,000 doses of GSK's Arepanrix H5N1 vaccine, made for clade 2.3.4.4b, for people with higher exposure to infected animals [Public Health Agency of Canada, 2025].

Because flu viruses change, a vaccine made for today's strain might not fully protect against a future pandemic strain. Twice a year, the World Health Organization reviews new virus data with experts to decide whether more candidate vaccine viruses are needed for pandemic preparedness [World Health Organization, 2026].

Can a Respirator or Mask Protect Against Bird Flu?

For the general public, avoiding contact with sick or dead animals offers far more protection than wearing a mask. For workers and others in direct or close contact with sick or dead animals or contaminated materials, the CDC recommends a NIOSH-approved particulate respirator such as an N95, ideally fit-tested. It also recommends unvented or indirectly vented goggles, disposable gloves, fluid-resistant coveralls, boots or boot covers, and a head cover [Centers for Disease Control and Prevention, 2024b]. People with respiratory, sensory or physical disabilities who find a respirator hard to wear should talk with their employer or health care provider about alternatives and fit.

Lowering Your Risk of Bird Flu

Most prevention steps are simple:

• Avoid direct contact with sick or dead wild birds, and watch wild birds only from a distance.
• Do not touch or drink raw milk or raw milk products. Choose pasteurized milk, since pasteurization inactivates avian flu viruses.
• Wear recommended protective equipment if you must handle sick or dead birds or other animals.
• Wash your hands often, especially after contact with animals or their environments.

These steps come from the CDC [Centers for Disease Control and Prevention, 2025b] and the World Health Organization [World Health Organization, 2026]. Caregivers of older adults and people with disabilities who keep backyard birds can lower risk by doing the flock cleaning themselves or with protective gear, so that the person at higher risk does not have to.

Eating Poultry and Eggs Safely

The World Health Organization reports no evidence that avian influenza spreads to people through properly prepared and cooked poultry or eggs [World Health Organization, 2026]. Cooking poultry, eggs and beef to the proper internal temperature kills avian flu viruses [Centers for Disease Control and Prevention, 2025b]. The USDA's safe minimum internal temperature for chicken is 165 degrees Fahrenheit (74 degrees Celsius), checked with a food thermometer in the innermost part of the thigh and wing and the thickest part of the breast [U.S. Department of Agriculture Food Safety and Inspection Service, n.d.].

Basic kitchen hygiene adds protection. Wash your hands before and after handling raw meat, keep raw poultry away from ready-to-eat foods, do not put cooked food back on a plate that held raw meat, and clean cutting boards, utensils and counters after use. Freezing does not kill flu viruses, so frozen poultry needs the same care as fresh.

Tips for Travelers

The World Health Organization advises travelers to avoid poultry farms, live poultry markets and areas where poultry may be slaughtered. Travelers who return from an affected area with respiratory symptoms should contact local health services and mention where they have been [World Health Organization, 2026]. Regular handwashing, avoiding contact with sick or dead birds, and eating only well-cooked poultry and eggs are sensible precautions anywhere avian flu is circulating.

If Someone You Know Is Diagnosed With Bird Flu

A bird flu diagnosis is serious but is not a death sentence - many people recover, especially with early antiviral treatment. Public health officials will usually ask about the person's animal exposures and may monitor close contacts. In the Washington H5N5 case, officials monitored about 135 health care workers, family members and others, and none became infected [Kibiger et al., 2026]. If you live with or care for someone who is ill, follow the advice of local health officials. They may recommend testing, watching for symptoms, or preventive antiviral medication.

Frequently Asked Questions

Can you get bird flu from eating eggs?

There is no evidence that bird flu spreads to people through eggs that have been properly handled and cooked. Cook eggs until the yolks and whites are firm, and avoid recipes that use raw or runny eggs during outbreaks.

What should I do if I find a dead wild bird?

Do not touch it with bare hands. Report it to your state or local wildlife or agriculture agency, or in the United States to the USDA at 1-866-536-7593, and if you are told to dispose of it, use gloves or pick it up with a plastic bag turned inside out.

Does the seasonal flu shot protect against bird flu?

No, the seasonal flu vaccine does not protect against H5N1. The CDC still advises people who work with potentially infected animals to get it, because it lowers the chance of being infected with seasonal and avian flu at the same time.

Can antiviral medicine be taken after exposure but before symptoms start?

Yes, in some cases. The CDC says people with certain exposures, such as contact with infected animals or raw milk without proper protective equipment, may be offered oseltamivir twice daily for five days as a preventive measure.

Can cats and other pets catch bird flu?

Yes, H5N1 has infected domestic animals, including cats. Keep pets away from sick or dead birds, and do not feed them raw poultry or raw milk from areas where the virus is circulating.

How is bird flu confirmed in a patient?

Bird flu can only be confirmed by laboratory testing of samples such as nose, throat or eye swabs, often by a public health laboratory. Tell your provider about any animal exposure so the right tests are ordered quickly.

Are hunters at risk of bird flu?

Hunters who handle wild ducks and geese can be exposed. Wear gloves while dressing birds, do not eat, drink or smoke while handling them, wash hands and tools afterward, and cook game birds to 165 degrees Fahrenheit.

Is it safe to keep backyard chickens?

Backyard flocks can be kept safely with good precautions. Keep wild waterfowl away from your birds and their water and feed, wear gloves and a mask when cleaning coops, and report sudden illness or deaths in your flock to your state veterinarian or agriculture department.

References

• Centers for Disease Control and Prevention. (2024a). About bird flu.
• Centers for Disease Control and Prevention. (2024b). Highly pathogenic avian influenza A(H5N1) virus: Interim recommendations for prevention, monitoring, and public health investigations.
• Centers for Disease Control and Prevention. (2025a). First H5 bird flu death reported in United States.
• Centers for Disease Control and Prevention. (2025b). Preventing bird flu infections.
• Centers for Disease Control and Prevention. (2025c). Treatment of bird flu.
• Centers for Disease Control and Prevention. (2026). A(H5) bird flu: Current situation.
• Centers for Disease Control and Prevention. (n.d.-a). 1957-1958 pandemic (H2N2 virus).
• Centers for Disease Control and Prevention. (n.d.-b). 1960-1999 highlights in the history of avian influenza (bird flu) timeline.
• Centers for Disease Control and Prevention. (n.d.-c). 1968 pandemic (H3N2 virus).
• Centers for Disease Control and Prevention. (n.d.-d). History of 1918 flu pandemic.
• Centers for Disease Control and Prevention. (n.d.-e). Types of influenza viruses.
• Kibiger, L., Oltean, H. N., Leitz, L., Krause, E., Barrett, D., Halloran, A., Yomogida, K., Lipton, B., Paris, K., Keirn, J., Buswell, M., Black, A., Trinh, P., Murray, T., Bonaccorso, R., Banuelos, L., Dieringer, E., Lenahan, J., Spence Davizon, E., ... Lindquist, S. (2026). Fatal human case of highly pathogenic avian influenza A(H5N5) in a backyard flock owner - Washington, November 2025. Morbidity and Mortality Weekly Report, 75(17), 221 - 225.
• Public Health Agency of Canada. (2024). Statement from the Public Health Agency of Canada: Update on avian influenza and risk to Canadians.
• Public Health Agency of Canada. (2025). Government of Canada purchases avian influenza vaccine to protect individuals most at risk.
• U.S. Department of Agriculture Animal and Plant Health Inspection Service. (2026). H5N1 highly pathogenic avian influenza.
• U.S. Department of Agriculture Food Safety and Inspection Service. (n.d.). Chicken from farm to table.
• U.S. Food and Drug Administration. (2024). AUDENZ.
• World Health Organization. (2026). Influenza (avian and other zoonotic) [Fact sheet].
• World Health Organization. (n.d.). Avian influenza A(H5N1) virus. Global Influenza Programme.
• World Health Organization Regional Office for the Western Pacific. (2026). Avian influenza weekly update number 1053.

Curated and edited by Ian C. Langtree, Founder and Editor-in-Chief, Disabled World. This section is maintained by the Disabled World editorial team. Last updated: 2 Nov 2026