US’ first human case of bird flu not linked to animals reported in Missouri

A person in Missouri is the United States’ first case of H5 avian influenza without a known exposure to a sick animal, the US Centers for Disease Control and Prevention said on Friday.

“This is the 14^th human case of H5 reported in the United States during 2024 and the first case of H5 without a known occupational exposure to sick or infected animals,” the CDC said in a statement. It’s also the first H5 case detected through the country’s national flu surveillance system rather than targeted surveillance of the ongoing bird flu outbreak in animals.

The case is under investigation by the Missouri Department of Health and Senior Services. The person had underlying medical conditions and was hospitalized on August 22. The person tested positive for influenza A, was treated with influenza antiviral medications and is now recovered and at home, according to MDHSS.

A sample from the patient was sent to the CDC, which confirmed that the case was a type of bird flu. Flu viruses are classified based on two proteins that sit on the surface of the virus an H, or hemagglutinin, protein, and an N, or neuraminidase, protein. A spokesperson for the CDC said the agency had confirmed the flu type is H5, but has not yet determined the N type. They are working on isolating the virus and reading its genetic sequence. Scientists at the CDC hope to have more information on the genetics of the virus in the coming days, the spokesperson said.

Knowing the genetic sequence will tell researchers how closely the virus that infected this patient may be related to the viruses that currently causing outbreaks in chickens, and cows and other mammals in the US.

There are no cases of bird flu among cattle in Missouri, but there have been outbreaks of the virus among poultry in the state.

The CDC’s risk assessment of H5N1 for the general public remains low, the agency said.

CNN’s Brenda Goodman contributed to this report.