Is Bird Flu a Risk to Humans?

The third human case tied to a dairy cow outbreak is reported in the U.S.

Rachel Nania,

AARP

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En español

Published March 21, 2023

/ Updated May 30, 2024

Matthew Hatcher/AFP via Getty Images

Another person in the U.S. has been diagnosed with avian influenza, also known as bird flu, associated with a multistate outbreak in dairy cows. The individual, a dairy farmworker in Michigan, is the second person in the state and the third person in the U.S. to test positive for the virus amid the bovine outbreak.

The first human case was confirmed in April, and the second was reported in mid-May. In both cases, the patients, who had been exposed to dairy cattle, only reported eye symptoms, according to the Centers for Disease Control and Prevention (CDC).

The third and latest individual experienced upper respiratory tract symptoms — including cough with no fever — along with eye irritation.

Even with this latest case, the CDC said on May 30 that the risk to the general public remains low, since risk depends on exposure to infected animals.

“However, this development underscores the importance of recommended precautions in people with exposure to infected or potentially infected animals. People with close or prolonged, unprotected exposures to infected birds or other animals (including livestock), or to environments contaminated by infected birds or other infected animals, are at greater risk of infection and should take precautions,” the CDC said.

Here’s what you need to know about the evolving situation.

What is bird flu?

Just like humans can get infected with influenza, different versions of the virus can infect animals, including birds.

Bird flu is caused by influenza A viruses that spread among wild aquatic birds (ducks, geese, gulls, etc.) and can infect poultry (chickens and turkeys).

Bird flu can infect other animals, as is the case with the H5N1 strain, which has been detected in mammals such as foxes, bears, seals, mountain lions and, most recently, cows. Since March 25, cases in cattle have been confirmed in several states, including Texas, Kansas, Colorado, New Mexico and Michigan.

Matthew Binnicker, director of clinical virology at Mayo Clinic, tells AARP that infections in mammals often happen when the animal either eats infected birds or encounters a carcass. Mammals exposed to environments with a high concentration of the virus are also susceptible to infection, Tim Uyeki, M.D., the chief medical officer of the CDC’s Influenza Division, said in an “Ask the Expert” post.

Are humans at risk from bird flu?

Bird flu infections in humans remain rare, health officials say, especially among those who are not in close contact with birds or other infected animals.

Infections can happen when the virus gets into a person’s eyes, nose or mouth or is inhaled, and symptoms can range from mild to severe. Importantly, we have yet to see sustained human-to-human transmission of bird flu, says Sabrina Assoumou, M.D., an infectious disease physician at Boston Medical Center and a professor of medicine at Boston University’s Chobanian and Avedisian School of Medicine.

“However, because of the possibility that bird flu viruses could change and gain the ability to spread easily between people, monitoring for human infection and person-to-person spread is extremely important for public health,” the CDC says.

Initial testing among the most recent cases infecting cattle in the U.S. did not detect any changes to the virus that would indicate it’s more transmissible to humans, the U.S. Department of Agriculture announced.

“This virus is being closely monitored, and we have not seen signs of sustained human-to-human transmission at this point,” Natasha Bagdasarian, Michigan’s chief medical executive, said in a May 22 news release from the state’s Department of Health and Human Services.

The CDC says more human cases could be identified; however, “sporadic human infections with no ongoing spread will not change the CDC risk assessment for the U.S. general public,” which, again, is low.

What about bird flu vaccines and treatments?

Your seasonal flu shot won’t protect you from a bird flu infection, but the CDC has vaccine formulas ready that target bird flu, and they could be used if the virus spread among people.

The antiviral treatments approved for seasonal influenza are recommended for people infected with avian influenza, including H5N1, according to the CDC. Because antiviral treatments work best when started as soon as symptoms begin, contact your state or local health department and a health care provider right away if you get sick after being in close contact with potentially infected birds.

Symptoms of bird flu and seasonal flu are similar. Keep an eye out for:

Fever
Chills
Cough
Sore throat
Shortness of breath
Headaches
Runny or stuffy nose
Body aches
Diarrhea

What can you do to lower your risk of infection?

The advice from health experts is to exercise caution around sick or dead animals.

“If you own poultry or have birds on your property and any [of them] come down with an illness or die, do not handle the birds,” Binnicker says. “Contact your local or state public health officials to come and investigate.” (To keep your flocks from getting infected, take steps to prevent their exposure to wild birds, which carry the disease and don’t always appear sick.)

The same goes if you’re out hunting and come across dead animals or birds — don’t touch the carcass. “Because, again, the cases that have occurred in humans have been from direct interaction and exposure with an infected or dead animal,” Binnicker says.

Be sure to cook your poultry and eggs to an internal temperature of 165°F to kill bacteria and viruses, including bird flu viruses, the CDC says. Given the latest infections popping up in cows, avoid unpasteurized (raw) milk or products made from raw milk such as cheeses. There are not safety concerns with the commercial milk supply, federal health agencies say, because products are pasteurized — heated to a certain temperature for a specific period to kill any germs present — before entering the market.

“And then from the human side, just the lessons that we’ve learned through the pandemic: If you have a respiratory illness, stay home. If you have to go out in public, wear a mask and go get tested, because finding out what the cause of the disease is, that is also still very important,” Binnicker says. A health care provider can test you for bird flu with a swab of the nose or throat.

Editor’s note: This story, first published March 21, 2023, has been updated to include new information.

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