Public Health

H5N1 bird flu: Questions patients may have and how to answer

Sara Berg, MS , News Editor

Concerns swirl across the country as highly pathogenic avian influenza (HPAI) A(H5N1) virus—commonly known as avian influenza or H5 bird flu—once again takes flight. This avian influenza strain has killed millions of wild birds and caused sporadic outbreaks among poultry. Now there is a multistate outbreak among dairy cows in the U.S.

While bird flu is rare in humans, three cases have been reported in the U.S. April marked the first report of a cow-to-human case of HPAI A(H5N1) virus infection in a dairy worker in Texas. The Centers for Disease Control and Prevention (CDC) confirmed a second human case of bird flu in late May in a dairy worker in Michigan, where the virus has also been identified in dairy cows. Both patients only reported eye symptoms associated with conjunctivitis.

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In a third case, another dairy worker in Michigan had eye symptoms as well as respiratory symptoms—congestion, sore throat, cough, fatigue, and “runny” and burning eyes—that are more typical of human influenza infections.

Previously, the A(H5N1) virus was confirmed in a person in Colorado in 2022 from exposure to poultry . The patient reported fatigue as their only symptom and fully recovered.

Meanwhile, the U.S. Department of Agriculture has reported that dairy cattle herds in nine states have confirmed cases of A(H5N1) virus infections. While A(H5N1) virus causes less severe illness in cattle than in poultry, the disease remains a concern for all livestock and also for humans who come into contact with infected animals.

Here are some questions patients might have about A(H5N1) virus, along with the answers that physicians should be ready to share. Visit the AMA bird flu (H5N1) resource center to learn more.

HPAI A(H5N1) virus is a type of influenza virus that causes highly infectious and severe respiratory disease in birds. That is why it is called avian influenza or bird flu. It is causing outbreaks in poultry and dairy cows in the U.S. And while the current public health risk for the general public is low, the CDC is carefully watching the situation and working with states to monitor people with animal exposures.  

They range from no symptoms to mild, flu-like illness to severe illness that requires hospitalization. For example, the dairy workers infected in the U.S. reported mild illness, with the main symptoms being conjunctivitis or eye infection.

Some other common symptoms are consistent with the flu, according to the CDC, and include cough, sore throat, eye redness or discharge, fever or feeling feverish, runny nose, fatigue, muscle or joint pain and headache. For moderate to severe illness, symptoms can include shortness of breath, difficulty breathing and altered mental state or seizures.

People who are exposed should monitor themselves daily for signs and symptoms of new illness for up to 10 days after the last known exposure. The incubation period depends on the strain of the virus, the dose, the route of exposure and the species. Available data suggests that the estimated incubation period for human infection with A(H5N1) virus is generally three to five days, but has been reported to be as long as seven to 10 days.

The A(H5N1) virus infection in people cannot be diagnosed by clinical signs and symptoms alone. Laboratory testing is needed to confirm A(H5N1) virus infection in humans.

Physicians and other health professionals should notify their state and local health departments to arrange testing for influenza A(H5N1) virus. They should also collect respiratory specimens from the patient to test for influenza A(H5N1) virus at the health department. If the exposed person has conjunctivitis, with or without respiratory symptoms, both a conjunctival swab and a nasopharyngeal swab should be collected for testing.

The risk of A(H5N1) virus infection is low for the general public in the U.S. But people who work with birds, poultry or cows, or have recreational exposure to them, are at higher risk.  

People rarely get A(H5N1) virus infections, but when they do, it is most often acquired through close, prolonged and unprotected contact—no gloves, protective wear, face masks, respirators or eye protection—with infected birds or other animals.

Human infections with avian influenza A viruses can happen when enough virus gets into a person’s eyes, nose or mouth, or is inhaled. This can happen when the virus is in the air in droplets or dust and a person breathes it in or when a person touches something that has the virus on it and then touches their mouth, eyes or nose, according to the CDC.

Standard, contact and airborne precautions are recommended for patients presenting for medical care or evaluation who have illness consistent with influenza and recent exposure to birds or other animals potentially infected with HPAI A(H5N1) virus. 

If signs and symptoms compatible with avian flu are present, physicians should isolate the patient and follow infection-control recommendations, including the use of personal protective equipment.

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There is Food and Drug Administration-approved antiviral treatment for seasonal flu that can be used for A(H5N1) virus infection. Antiviral treatment is recommended with oseltamivir as soon as possible for outpatients and hospitalized patients who are suspected, probable or confirmed cases of human infection with A(H5N1).

Starting empiric antiviral treatment with oral or enterically administered oseltamivir—twice daily for five days—is recommended regardless of time since onset of symptoms. Antiviral treatment should not be delayed while waiting for laboratory test results. And while there is currently no indication of the disease spreading further among humans, these patients should isolate to reduce risk of infecting others

Antiviral treatment works best when started early after symptoms begin. Antivirals can also be given soon after unprotected exposure—such as not using respiratory and eye protection—to prevent infection and illness. When influenza viruses evolve, it can make treatment less effective. The CDC regularly tests bird flu viruses for antiviral resistance.

There are H5 candidate vaccine viruses that could be used to produce a vaccine. According to the

U.S. Department of Health and Human Services’ assistant secretary for preparedness and response,  officials are moving ahead with a plan to produce 4.8 million doses of H5N1 avian flu vaccine for pandemic preparedness. Active discussions are underway across federal agencies about what the key triggers would be for deploying H5N1 vaccine doses.

Testing for the flu typically declines over the summer, but the CDC is working on a plan for enhanced nationwide monitoring to ensure that even rare cases of A(H5N1) virus in the community are detected. This includes increasing the number of influenza virus specimens that are tested and then subtyped in public health laboratories that can detect A(H5N1) virus.

Additionally, the federal government is offering financial incentives to dairy-farm owners to encourage broader testing of cattle and expand biosecurity measures to control the growing outbreak. It is only available to farms with infected herds. Testing of cattle and farm workers is important to controlling this outbreak.

Since the A(H5N1) virus is not spreading among humans, most people don’t need to worry about precautions. But the best prevention is to avoid sources of exposure. That means avoiding direct contact with wild birds and other animals infected with, or suspected to be infected with, bird flu viruses. Notably, wild birds can be infected with avian influenza even if they don’t look sick.

It is also important to avoid being near dead animals or surfaces contaminated with an animal’s feces or litter, raw milk, saliva, mucous or other byproducts when not wearing respiratory or eye protection. And, as always, people should not eat uncooked or undercooked food. They should avoid uncooked food products such as unpasteurized raw milk or cheeses from animals who have a suspected or confirmed infection, the CDC says.

The FDA has been sampling retail milk and other dairy products. To date, they have not found live, infectious virus in the products.

The CDC issued a Health Alert Network Health Advisory with recommendations that support consumption of only pasteurized milk and dairy products made from pasteurized milk. Most of the nutritional benefits of drinking milk are available from pasteurized milk. It is important not to consume unpasteurized “raw” milk or products made from unpasteurized milk because it can contain bacteria or viruses, such as A(H5N1) virus, that can cause serious illness, hospitalization or death. The CDC has developed advice for health care professionals on raw milk (PDF).

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There is no evidence that the virus can be transmitted to humans through properly prepared food. Cooking poultry, eggs and other animal products to the proper temperature and preventing cross contamination between raw and cooked food are key to preventing any food safety hazard, including infection from the A(H5N1) virus, according to the FDA .

It is important to avoid contact with wild or domestic birds that appear ill or have died. If you do encounter a sick or dead bird, call to report it because wildlife agencies regularly investigate reports of sick or dead animals. This type of reporting can help with early detection of illnesses such as the bird flu or West Nile virus, according to the CDC.

The CDC does not have any travel restrictions related to the bird flu to states or countries affected by avian influenza in wild birds, poultry, other animals or people. But travelers to countries or states with bird-flu outbreaks in poultry or people should not visit poultry farms, bird markets or other places where live poultry are raised, kept or sold.

When traveling—just as at home—do not eat raw or undercooked poultry products and wash your hands after touching uncooked poultry. Beyond that, practice good hygiene and visit a doctor if you become sick during or after travel.