H5N1 usually spreads to people through contact with infected or dead birds, as with the Louisiana patient. Currently, there are no known cases of human-to-human transmission, said the CDC's Dr. Demetre Daskalakis.

A genetic analysis of viral samples from a patient in Louisiana hospitalized with the first severe case of bird flu showed mutations that may result in the virus becoming more transmissible

A person in Louisiana has the first severe illness caused by bird flu in the U.S., health officials said Wednesday.

In a case first reported in Louisiana, a patient has now developed the first known case of bird flu so severe as to require hospitalization.

The CDC has confirmed a total of 66 human cases of bird flu across the United States as of Friday, although the number is believed to be higher.

Fox News senior medical analyst Dr. Marc Siegel explains what's behind human cases of bird flu in U.S.

A patient in Louisiana became severely ill after contracting Highly Pathogenic Avian Influenza (HPAI), the US Centers for Disease Control and Prevention (CDC) announced in a statement on Thursday. This is the first serious case of bird flu affecting a human reported in the US since the outbreak began.

The virus in the first severe human bird flu case in the U.S. was found to have mutated. Follow Newsweek's live blog for updates.

A genetic analysis of samples from the patient in Louisiana recently hospitalized with the country’s first severe case of H5N1 bird flu show the virus likely mutated in the patient to potentially become more transmissible to humans,

The CDC warns samples of the bird flu virus show signs of mutations that could make it more transmissible to humans. The CDC says it appears the H5N1 virus contained mutations in the Louisiana patient who contracted the nation’s first severe case of the illness.