Amid a "concerning" new mutation in bird flu that may indicate the virus could begin to more easily infect humans, what are the symptoms to watch for and how worried should you be?
Since March, more than 60 bird flu infections in people have been reported in the U.S., but previous illnesses have been mild and most have been detected among farmworkers exposed to sick poultry or dairy cows. In two cases — an adult in Missouri and a child in California — health officials have not determined how they caught it.
Earlier this month, health officials confirmed the first known severe illness in the U.S., and California's governor declared a state of emergency as the virus rampages through dairy cattle in that state.
In the Midwest, cases have been confirmed in Iowa, Michigan, Missouri and Wisconsin.
Here's what to know:
What is bird flu?
According to the Centers for Disease Control and Prevention, bird flu is "a disease caused by avian influenza A viruses that usually spread between birds."
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Who can contract bird flu?
Bird flu has been spreading for years in wild birds, chickens, turkeys and many other animals. It was first confirmed in U.S. dairy cattle in March.
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While the virus typically doesn't infect humans, one subtype, known as H5, is spreading around the globe in wild birds and causing outbreaks in U.S. poultry and dairy cows. This particular strain, known as H5N1, has also led to human infections.
In total six subtypes of bird flu viruses have infected humans, according to the CDC. They include: H3, H5, H6, H7, H9, and H10.
CDC officials said that bird flu is still mainly an animal health issue and that the risk to the general public remains low. There has been no documented spread of the virus from person to person, said the CDC's Dr. Demetre Daskalakis.
What about pets?
Though cases of infection are rare, cats also seem especially susceptible to the bird flu virus, or Type A H5N1. Even before the cattle outbreak, there were feline cases linked to wild birds or poultry. Since March, dozens of cats have caught the virus. These include barn and feral cats, indoor cats, and big cats in zoos and in the wild.
A voluntary recall was issued for a line of raw and frozen pet food after a cat died of bird flu, a case that Oregon officials connected to the feline’s contaminated food.
Dogs seem to be less vulnerable than cats, but they should eat only thoroughly cooked foods, Bailey said.
How is bird flu spread?
When a person does contract bird flu, it's most often through direct contact with infected birds or other infected animals, the CDC states.
While no known human-to-human spread of the virus has been reported in cases currently circulating, there have been some such cases in years past, but even then, the cases were limited.
"The spread of bird flu viruses from one infected person to a close contact has occurred rarely in other countries in the past, and when it has happened, it has been limited and not sustained, and did not spread beyond close contacts," the CDC reported.
How worried should you be?
A genetic analysis suggests the bird flu virus mutated inside a Louisiana patient who contracted the nation’s first severe case of the illness, the U.S. Centers for Disease Control and Prevention said this week.
Scientists believe the mutations may allow the virus to better bind to receptors in the upper airways of humans — something they say is concerning but not a cause for alarm.
Michael Osterholm, a University of Minnesota infectious disease researcher, likened this binding interaction to a lock and key. To enter a cell, the virus needs to have a key that turns the lock, and this finding means the virus may be changing to have a key that might work.
“Is this an indication that we may be closer to seeing a readily transmitted virus between people? No,” Osterholm said. “Right now, this is a key that sits in the lock, but it doesn’t open the door.”
The CDC said its findings about the mutations were “concerning,” but the risk to the general public from the outbreak “has not changed and remains low.”
Still, Osterholm said, scientists should continue to follow what’s happening with mutations carefully.
“There will be additional influenza pandemics and they could be much worse than we saw with COVID," he said. "We know that the pandemic clock is ticking. We just don’t know what time it is.”
"Virus hunter" Mary Rodgers, an associate research fellow at Abbott, agreed.
"We certainly have been keeping an eye on H5N1, which is avian influenza, in particular in the U.S. because we're seeing more and more human cases lately," Rodgers told NBC Chicago. "These are primarily in people who are at risk because they're interacting with livestock ... but that could always change. And so that's why we have to keep an eye on it as people get cases."
Some experts say the signs are going in the wrong direction.
“The traffic light is changing from green to amber,” Dr. Peter Chin-Hong, a professor of medicine at the University of California, San Francisco, who studies infectious diseases, told NBC News. “So many signs are going in the wrong direction.”
What are the symptoms of bird flu?
According to the CDC, symptoms typically range from no symptoms at all to mild symptoms, though some may experience more moderate to severe complications.
The most common symptom associated with recent infections has been eye redness.
Mild signs and symptoms may include:
- eye redness and irritation (conjunctivitis)
- mild fever (temperature of 100ºF [37.8ºC] or greater) or feeling feverish
- cough
- sore throat
- runny or stuff nose
- muscle or body aches
- headaches
- fatigue
Less common symptoms include diarrhea, nausea, or vomiting.
Signs and Symptoms of Moderate to Severe Disease
- high fever
- shortness of breath or difficulty breathing
- altered consciousness
- seizures
Symptoms in pets
Cats sick with bird flu might experience loss of appetite, lethargy and fever.
If your cat is usually playful and likes to look out the window, but instead has been sleeping all the time or hiding from you, take note," Dr. Michael Q. Bailey, president-elect of the American Veterinary Medical Association, said. “There’s something wrong."
They could have reddened or inflamed eyes and discharge from the eyes and nose. They might have difficulty breathing or have tremors or seizures.
If your cat is sick, call your veterinary clinic and keep the cat away from anyone with a weakened immune system.
How is it treated?
There are flu antiviral drugs that can treat infections, but those who are infected should be treated as soon as possible, experts say. The treatments work best if given within 48 hours of developing symptoms.
