What to know about the latest bird flu outbreak in the US

A poultry farm in Michigan and an egg producer in Texas both reported bird flu outbreaks this week. The latest developments in the virus also include infected dairy cows and the first known case of a human catching bird flu from a mammal.

While health officials say the risk to the public remains low, there is growing concern, partly following news that the largest producer of fresh eggs in the US has reported an outbreak.

Here are some important things to know about the disease.

Dr. Mandy Cohen, director of the Centers for Disease Control and Prevention, told The Associated Press on Wednesday that the agency is taking bird flu seriously, but emphasized that the virus has already been well studied.

“The fact that it is now occurring in livestock certainly increases our concern,” Cohen said, noting that this means farmworkers who work with livestock — and not just those who work with birds — may need to take precautions.

The good news is that “it is not a new strain of the virus,” Cohen added. “We know this and we have studied it, and honestly, we have been preparing for bird flu for 20 years.”

Some flu viruses mainly affect humans, others mainly occur in animals. Avian viruses spread naturally through wild waterfowl such as ducks and geese, and then to chickens and other domestic poultry.

The bird flu virus that is attracting attention today – Type A H5N1 – was first identified in 1959. Like other viruses, it has evolved over time and newer versions of itself have emerged.

Since 2020, the virus has spread among more species – including dogs, cats, skunks, bears and even seals and porpoises – in dozens of countries.

In the US, this version of bird flu has been found in wild birds in every state, as well as in commercial poultry farms and backyard flocks. Nationwide, tens of millions of chickens have died from the virus or been killed to prevent the spread of outbreaks.

Last week, US officials said it had been found in livestock. The disease was discovered Tuesday 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 identified as a threat to humans during a 1997 outbreak in Hong Kong. According to the World Health Organization, nearly 900 people worldwide have been diagnosed with bird flu and more than 460 have died in the past 20 years.

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

In 2022, an inmate in a work program caught the disease while killing infected birds on a poultry farm in Montrose County, Colorado. His only symptom was fatigue, and he recovered.

This week, health officials in Texas announced that a person who had come into contact with cows had been diagnosed with bird flu. Their only reported symptom was redness of the eyes.

The symptoms are similar to those of other flus, including coughing, body aches and fever. Some people have no noticeable symptoms, but others develop severe, life-threatening pneumonia.

The vast majority of infected people got the virus directly from birds, but scientists are on the lookout for any sign of spread among humans.

There have been a few cases where that apparently happened – most recently in 2007 in Asia. In each cluster, it spread within families from a sick person in the home.

US health officials have emphasized that the current risk to public health is low and that there are no signs of bird flu spreading from person to person.

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Associated Press reporters Jonathan Poet in Philadelphia and Mike Stobbe and videojournalist Sharon Johnson in Atlanta contributed to this report.