Bird flu: Your questions on symptoms, spread and safety answered

Bird flu is no longer only “for the birds.”

Infections have expanded beyond wild birds and poultry to a range of animals — from mice to mountain lions, dairy cows to domestic cats, and polar bears to people. The virus is becoming a threat we can’t ignore.

While the current risk for people is low, bird flu is spreading. Public health and disease experts across the country, including at Arizona State University, are tracking the virus, studying how and where it spreads, and preparing for what could come next.

Research happening at ASU provides some answers to common questions about bird flu and how to keep Arizona and the nation safe.

Bird flu, also called avian flu and H5N1, is a type A influenza. Flu comes in types A, B, C and D. Type A influenza is a more severe form of flu that can infect humans, birds and other animals. The ever-changing seasonal flu viruses include influenza type A as well as type B, a sometimes milder flu that only infects people.

This isn’t humanity’s first encounter with bird flu, but it is different from our past experiences. H5N1 cases in humans were first documented in Asia in 1997, according to data from the World Health Organization. Since then, the bird flu virus has circulated in wild and domestic birds in Asia, Africa and Europe. It has also caused periodic human infections in these regions.

In the past few years, the virus has spread to the United States. How did it get here? Migratory birds, which fly across oceans and continents far and wide, likely brought the virus to wild birds in North America. The virus has continued to spread among birds and now mammals.

Bird flu infections have the potential to be dangerous for people.

Currently, the majority of recent bird flu infections in humans have been mild. Of the 70 cases confirmed by the Centers for Disease Control and Prevention in the United States since 2024, only one person has died.

Past H5N1 bird flu outbreaks in Asia have had a greater than 50% fatality rate, “which makes it one of the deadliest known viruses,” says Dave Engelthaler, executive director of ASU’s Health Observatory and director of the northern Arizona division of Translational Genomics Research Institute, or TGen North.

Engelthaler says it’s important to share knowledge and capabilities to stay ahead of the virus. As it spreads, bird flu has the potential to transform into a more serious threat.

In early 2025, the ASU Health Observatory formed the Arizona Union for Pathogenic Avian Influenza Research. The group partners with experts at the University of Arizona, Northern Arizona University, TGen, and other health and wildlife experts to coordinate efforts.

“Members of the research community were the first to find bird flu in Arizona,” Engelthaler says.

The group’s efforts include tracking positive flu cases in people in the region, testing birds and monitoring wastewater for the presence of the bird flu virus from animals and people.

“We don't know what the next chapter is going to be,” Engelthaler says, “but we’ve really got to keep a close watch on it.”

Bird flu is not currently known to spread between people.

Bird flu is one of many zoonotic diseases, or illnesses people can catch from animals.

So far, human cases have largely been linked to exposure to sick or dead animals, including commercial poultry flocks, dairy cows and other animals. Be aware that not all infected animals look sick.

Infections happen when the virus comes in contact with a person’s eyes, nose or mouth. This can happen by interacting with a sick or dead animal, or from touching surfaces contaminated with the virus.

In humans, bird flu infections usually cause mild illness. The most common symptom is pink eye or conjunctivitis.

“What we normally see in almost every single case is these brilliantly bright, bloodshot eyes,” Engelthaler says.

Symptoms tend to appear between two and seven days after exposure to a sick or dead animal. Some people show no symptoms of infection, while others experience other mild to severe symptoms.

Mild symptoms in people include: bloodshot eyes, fever, cough, sore throat, runny or stuffy nose, muscle/body aches, headache and fatigue.

Severe symptoms include: high fever, shortness of breath or difficulty breathing, seizures, pneumonia, respiratory failure, organ failure and inflammation in the brain.

The person who was hospitalized and died from a bird flu infection was over 65 years old and had underlying medical conditions. In Canada, a teenager with asthma who tested positive for bird flu was also hospitalized. She experienced respiratory failure and pneumonia, but has since recovered.

Bird flu symptoms in chickens and other birds are not always clear. Some infected birds may show decreased egg production, respiratory symptoms, diarrhea or neurological symptoms. But there’s no clear telltale sign without testing the individual animal.

While the current risk of bird flu infections in people is low, the CDC has elevated the risk level to moderate or high for those who work with potentially infected livestock or other animals.

Infections spread quickly among birds in poultry farms. People in close contact with the birds and those responsible for culling infected flocks are often highly exposed to the virus.

On dairy farms, infected cows have been found to shed the virus in their milk. People who handle or drink raw milk, work with infected cattle or are exposed to contaminated farm environments can be at increased risk of infection.

Those at higher risk should watch for any bird flu symptoms. People should contact their doctors if they believe they may be infected or have had high-risk exposure.

The risk is currently low for many pets, but those that go outdoors where they may have contact with wild birds or livestock could catch bird flu.

Dogs can get bird flu infections, likely from contact with sick or dead birds outside or eating contaminated raw pet food. But dogs tend to only experience mild symptoms.

“Dogs would probably get over it if they got infected,” says Craig Woods, a licensed veterinarian who works as a biomedical consultant at ASU and in the region. “Cats — that’s another story.”

Cats are severely affected by the bird flu virus, which infects their nerves and brain. Many cases lead to serious respiratory or neurological symptoms and death. Both domestic house cats as well as big cats in zoos and out in the wild experience severe infections.

The biggest risk for cats is contact with infected wild birds. Cats have also contracted bird flu infections from drinking raw milk on dairy farms and eating raw pet food made with contaminated poultry.

Backyard chickens are also at high risk, particularly if they come into contact with migratory wild birds or their droppings.

The virus can remain in bird droppings, other fluids and body tissues, and the environment for some time. So the important thing for you and your pets, Woods says, is to limit exposure to potentially infected animals.

The best course of action for humans is to prevent exposure.

Following safety measures on farms and proper hand hygiene can help prevent infection. People should also avoid touching their faces after handling animals or working in their environments.

People who have suspected or confirmed cases of bird flu infection can be treated with antiviral medications. These include oseltamivir, also known by the brand name Tamiflu. Antivirals work best when started within 48 hours of showing symptoms.

The seasonal flu vaccine does not prevent H5N1 bird flu infections. The vaccine can still help prevent dangerous mutations that happen if someone is infected with both bird flu and another flu variety.

Bird flu vaccines are not currently available to the general public. However, building blocks for H5 flu virus vaccines are ready in case we need to create them.

There are currently no approved treatments for animals besides vaccinations for livestock. Most treatments for pets involve supportive care, such as alleviating symptoms when possible.

Pandemics can happen when a new subtype of influenza A emerges with mutations that allow it to infect people and spread rapidly. One recent example is the 2009–2010 H1N1 swine flu pandemic.

Viruses mutate, or make changes to their genetic code, when they make mistakes copying themselves in a host animal’s cells. Sometimes these changes do nothing or weaken the virus. Other times they make the virus stronger.

Flu viruses are prone to mutations because they can be especially sloppy when making copies.

They also easily combine with other flu viruses. So, when two distinct flu viruses infect the same host, they can trade features or merge to create a whole new version of the virus very quickly.

This is a major risk scientists are watching for in the current H5N1 bird flu outbreak.

Matthew Scotch, associate dean and a professor in the ASU College of Health Solutions, helps track the bird flu virus by studying its genes. He is also a member of the Arizona Union for Pathogenic Avian Influenza Research. His lab tracks viral evolution, patterns of transmission and the risk to wildlife and human health.

“Sequencing the current H5N1 bird flu virus helps us understand how it is evolving over time, including mutations that may influence its ability to spread, infect new hosts or evade immune responses,” Scotch says. “We can track changes in key regions of its genome, such as those affecting virulence (the ability to cause disease) and host adaptation.”

Scotch says the bird flu virus could pick up a mutation that helps it infect people.

“This shift would allow the virus to replicate more effectively in human airways,” Scotch says, “increasing the likelihood of airborne transmission.”

It takes a whole community of experts to track and address such a widely spread and volatile virus. 

From specialized state organizations watching wastewater or wildlife to national agencies monitoring the big picture of the agriculture industry, no one organization can do it alone.

• The U.S. Department of Agriculture and its Animal and Plant Health Inspection Service track outbreaks in wild and domestic birds. They also conduct testing and manage efforts to protect farms.
• The Food and Drug Administration checks foods like eggs for safety during outbreaks. It also regulates flu vaccines and antiviral medications that can be used to treat bird flu.
• The Centers for Disease Control and Prevention focuses on the human health risks of bird flu. They keep track of infections in people and how the virus evolves, and develop pandemic preparedness plans.
• The Administration for Strategic Preparedness and Response administers a strategic national stockpile of personal protective equipment and antiviral medicine that can be sent to high-risk areas. The administration also has a reserve of raw materials ready to quickly create vaccine doses.
• State and local health agencies work on the front lines of outbreaks. They do testing and reporting activities and help health care institutions to be more prepared for large emergencies.

State and local agencies also fill an important role in communicating with farmers and the public about risks. They implement public health laws and policies to help assess, prevent and control the spread of the virus.

Those agencies in Arizona rely on support from the ASU Health Observatory and the Center for Public Health Law and Policy at the Sandra Day O’Connor College of Law.

James G. Hodge Jr. leads the center, which provides real-time information and guidance for emerging and pressing challenges at the intersection of law, ethics, policy and public health.

“We have an extensive array of legal and policy options available,” says Hodge, the Peter Kiewit Foundation Professor of Law. “But we must exercise these options efficiently to prevent bigger repercussions for humans.”

Testing, screening and other disease monitoring interventions are designed to prevent the spread of infections.

For example, if a person comes to an emergency room with symptoms that could be a bird flu infection, they may be asked about potential exposures or tested for the virus, Hodge says.

In the case of a true emergency — such as a large influx of H5N1 cases in a given area or human-to-human spread — state agencies are ready to deploy a range of additional public safety tools to keep communities safe.

“These public health interventions save lives in emergencies involving emerging infectious diseases,” Hodge says.

The current state of bird flu has not reached emergency levels in most places, but preparedness is always key with a highly mutable virus like H5N1.

“We may not have passed the last pandemic test with flying colors, but we learned a lot. I do think we are smarter, more capable and hopefully more prepared to respond as a community,” Engelthaler says.

“For now, we just need to keep watching and do what we can to keep each other healthy.”