What You Need to Know About Bird Flu

Key Takeaways

• Bird (avian) flu has infected tens of millions of chickens in the United States as well as dairy cows and cattle and, recently, a dairy-farm worker.
• The risk to most people in the States is minimal, experts say.
• For safety, avoid drinking unpasteurized milk; pasteurized milk and eggs pose little risk.

A global bird flu outbreak infecting record numbers of chickens and wild birds as well as dairy cows, cattle, and other mammals is raising concerns about whether the influenza A/H5N1 variant circulating right now might become a significant risk to humans.

Another worry is whether eggs and milk are currently safe to consume given the number of affected animals.

The bird (avian) flu outbreak is the largest on record in the United States, already infecting more than 82 million chickens, according to the U.S. Department of Agriculture (USDA).

Every state has found cases in wild birds, and all but three had outbreaks in poultry. Bird flu is also spreading to mammals, according to the USDA.

A variety of animals have been infected, including skunks, bobcats, foxes, raccoons, mountain lions, bears, possums, dolphins, seals, and coyotes. The World Health Organization (WHO) confirmed the second human case of bird flu in the United States in an April 9 statement.

The infected person was a worker at a commercial dairy farm in Texas who developed conjunctivitis (pink eye) in response to the virus. "It also appears to be the first human infection with A(H5N1) acquired from contact with an infected mammal," the WHO said.

Right now the danger to the general public is minimal, according to the WHO. Even for people who work with birds or mammals that can carry these infections, WHO said the risk remains low to moderate.

But experts say worries about the threat of bird flu to humans and a potential pandemic are justified.

Here, Richard Webby, PhD , an infectious disease researcher at St. Jude Graduate School of Biomedical Sciences in Memphis, Tennessee, and the director of the WHO Collaborating Center for Studies on the Ecology of Influenza in Animals and Birds, answers the most pressing questions on bird flu.

Everyday Health: What is bird flu, and how is it different from other kinds of flu?

Dr. Richard Webby: Bird flu is a terrible term. Essentially it encompasses a wide variety of different influenza viruses. In the current situation the best way to help people think about this is to think about COVID-19 with many variants. Influenza also has a range of different variants. The main types that cause seasonal flu in people in the United States are limited to four variants. For avian flu, there are 16 variants in birds. What we have right now [in the current outbreak] is one of those avian flu variants, the H5 virus.

EH: Why are so many birds and mammals getting bird flu?

RW: The problem with H5 is that it has become very adept at infecting migrating birds like ducks. When birds move they bring the virus with them and they spread it to other bird species. Birds of prey like eagles or raptors are probably getting it from eating sick ducks. We are seeing mammals like foxes or skunks getting it, and they are scavenging and probably getting it from feeding on carcasses of infected birds.

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We have also now seen cows infected. It is a little unclear how this happened, and infection of this host is a bit of a surprise. It does look like a bird virus somehow infected a cow, and we are now seeing cow-to-cow spread.

EH: Can people get bird flu?

RW: This virus does have the potential to transform from a bird virus to a human virus, but it seems right now to be very difficult for this particular H5 virus to jump to humans; the virus maintains all the characteristics of a virus that will stay within birds. But the risk is not zero, and people have been infected, including one worker on an infected dairy cow farm.

EH: What happens to people who get bird flu? Can they get very sick or die?

RW: We have seen H5 for 25 years, and in all this time we have seen hundreds of people get infected. We haven't ever seen it move from human to human.

The human fatality rate is running at about 50 percent, but we have to take this number with a little bit of a grain of salt because we are only detecting people who get really sick and see a doctor. The virus is probably infecting more people who don't get sick, who get infected and are asymptomatic. The most recent case of the dairy cow worker resulted in conjunctivitis and not respiratory disease.

What we do know about this virus is that it has a bigger potential risk for severe disease than seasonal flu because the infection can go deeper down into the lungs.

EH: Are there certain people who are more likely to get bird flu?

RW: Anything you do that increases the risk of coming into contact with an infected bird could increase your risk. Over the past 25 years, most cases in humans have been in countries like China and Egypt, where many people keep birds and there are large poultry markets. Coming in contact with live or sick birds is the highest risk. In the current environment with ongoing cow infections, being in close contact with these animals also increases risk.

EH: Can you talk about bird flu symptoms, diagnosis, and treatment in humans?

RW: Symptoms of bird flu can be similar to seasonal flu symptoms , and you can get tested. There's a generic test for flu, and if somebody has bird flu this would be positive. Then if it's positive, there is a separate test for H5 that can detect bird flu. If people have flu-like symptoms and have been in contact with poultry or bird populations or infected cows, that elevates the possibility that it might be bird flu.

Two drugs that work for seasonal flu can also work for bird flu - baloxavir (Xofluza) and oseltamivir (Tamiflu) . The key is getting people treated early. The sooner people get treated, the better these drugs will work.

EH: What can people do to prevent catching bird flu? Is there a vaccine?

RW: There is a licensed H5 vaccine in the United States, but it's not for this particular version of H5 in circulation right now. It would probably provide some protection against what we're seeing right now, though. The United States has some stockpiles of some H5 vaccines, and manufacturers know how to make it. But people can't get a vaccine right now. It's all being held within national stockpiles.

EH: How worried should I be about bird flu in chickens and cows in terms of my food choices - do I need to be worried about eating eggs, drinking milk, or eating beef or chicken?

RW: Right now the biggest concern is drinking unpasteurized milk. We know that there are very large amounts of virus in the milk of infected dairy cows and drinking this milk is very risky.

There have been efforts to look for infectious virus in pasteurized milk and beef, which have all, luckily, turned up negative. There is little risk in consuming these products.

Similarly, eggs are not thought to be of concern. Infected chickens are rapidly removed or die, and the chances of an egg from an infected bird entering the food chain is essentially zero.

EH: What about my cat and my dog - can they get bird flu?

RW: If they're running around in the neighborhood and see a dead bird they chew on, there is a risk. Similarly, we have seen cats that have consumed infected milk from the cow dairy farms and have also contracted the disease. Big cats in the zoo do catch it; it's not like household cats and dogs are immune. We haven't seen any evidence of infected cats or dogs passing it to their owners.

EH: Big picture: How worried should people be about bird flu right now? Is this the next pandemic?

RW: It's really difficult to put this into context. Right now, this is a virus that for a human is very, very difficult to catch.

But if there's a flu virus I wouldn't want to catch - it's this virus. We've been following it for 25 years and it hasn't become widespread in humans. But we haven't seen it in South America before [it has been identified in animals there recently] and we've seen it only transiently in the United States in the past.

The risk may be very low for humans right now, but the relative risk is as high now as it has ever been. We know influenza viruses can make this jump from an animal virus to humans. Other types of bird flu - H1, H2, and H3 - have successfully made the leap.

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With the history of knowing that flu viruses can do this, there is absolutely the worry about this becoming a pandemic. There are 16 types of flu in birds and only three have successfully made it to humans. Some people read this as the other 13 types probably don't have the capacity to move to humans. I think they still have the potential to do this, but they don't do it easily, and it's a much lower risk. It's just not zero.

Editorial Sources and Fact-Checking

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Sources

1. Confirmations of Highly Pathogenic Avian Influenza in Commercial and Backyard Flocks. U.S. Department of Agriculture Animal and Plant Health Inspection Service. April 25, 2024.
2. Detections of Highly Pathogenic Avian Influenza in Mammals. U.S. Department of Agriculture Animal and Plant Health Inspection Service. May 1, 2024.
3. Avian Influenza A(H5N1) – United States of America. World Health Organization. April 9, 2024.