H5N1: What to know about the bird flu cases in cows, goats and people

Editor's note: This is a developing story and will be updated.

A bird flu virus called H5N1 recently infected Animals that it had never been seen in before: goats and cows.

Now, it's suspected that a person has picked up the infection after being exposed to infected cows.

Here's what we know so far about these unusual cases of H5N1 in the U.S.

Related: 21-year-old student dies of H5N1 bird flu in Vietnam

What is H5N1 bird flu?

H5N1 is a subtype of avian influenza A, a broad group of related bird flu viruses. It's categorized as a form of "highly pathogenic" avian influenza, or HPAI, because it causes severe and fatal disease in poultry. For example, H5N1 and other "H5" bird flu viruses can rapidly cause organ damage in chickens and kill up to 90% to 100% of chickens they infect, often within 48 hours, according to the Centers for Disease Control and Prevention (CDC). H5N1 has been responsible for the major bird flu outbreaks seen on U.S. poultry farms and on farms in other countries since 2022.

Although HPAI viruses are known for devastating domestic bird populations, H5N1 also infects wild birds and occasionally infects various maMMAls, including people. In non-avian species, it can still cause fatal disease, but some cases are mild or asymptomatic.