What you need to know about the latest outbreak of bird flu in the United States

This week, a poultry facility in Michigan and an egg production facility in Texas both reported outbreaks of avian influenza. The latest developments regarding the virus include the first case of human infection of avian influenza from infected dairy cows and mammals.

Health officials say the risk to the public remains low, but concerns are growing with news that the nation's largest raw egg producer has reported an outbreak.

Here are some important things to know about this disease.

Dr. Mandy Cohen, director of the Centers for Disease Control and Prevention, told The Associated Press on Wednesday that officials take bird flu seriously, but stressed that the virus is already well-studied.

“The fact that it's happening in cattle definitely raises our level of concern,” Cohen said, noting that farm workers who work with birds as well as those who work with cattle take precautions. He pointed out that it might be necessary.

The good news, Cohen added, is that “this is not a new virus.” “This is something we know, we study, and frankly, we've been preparing for bird flu for 20 years.”

Some influenza viruses primarily infect humans, while others primarily infect animals. Avian viruses naturally spread to wild waterfowl such as ducks and geese, and then to chickens and other poultry.

The avian influenza virus (type A H5N1) that is gaining attention today was first identified in 1959. Like other viruses, it evolved over time and gave rise to new versions.

Since 2020, the virus has spread to more animal species in many countries, including dogs, cats, skunks, bears, and even seals and porpoises.

In the United States, this version of avian influenza has been detected not only in wild birds in each state, but also in commercial poultry farms and backyard flocks. Nationwide, tens of millions of chickens have died from the virus or been culled to prevent the spread of infection.

Last week, U.S. authorities announced it had been detected in livestock. As of Tuesday, it had been found in dairy herds in five states: Idaho, Kansas, Michigan, New Mexico and Texas, according to the U.S. Department of Agriculture.

This bird flu was first recognized as a threat to people when it broke out in Hong Kong in 1997. According to the World Health Organization, nearly 900 people have been diagnosed with bird flu worldwide in the past 20 years, and more than 460 people have died.

There have only been two cases in the United States, and neither was fatal.

In 2022, a prison inmate in a work program was infected while slaughtering infected birds at a chicken farm in Montrose County, Colorado. His only symptom was fatigue and he recovered.

This week, Texas health officials announced that a person who came into contact with the cow was diagnosed with avian influenza. Their only reported symptom was red eyes.

Symptoms are similar to other influenzas, including cough, body aches, and fever. Some people have no noticeable symptoms, but others develop severe and life-threatening pneumonia.

The vast majority of cases have been transmitted directly from birds, but scientists are on the lookout for signs of infection in humans.

There are several examples where that clearly has happened, most recently in Asia in 2007. In each cluster, the infection spread from a sick person in the household to other family members.

U.S. health officials stressed that the current public health risk is low and there is no sign that bird flu can spread from person to person.

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Associated Press writers Jonathan Poet in Philadelphia, Mike Stobbe in Atlanta and video journalist Sharon Johnson contributed to this report.