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 ongoing spread of bird flu in the United States has alarmed experts -- not just because of human cases causing severe illness, but also due to troubling new instances of infections in cats.

The bird flu virus found in a severely ill patient hospitalized in the United States has mutated to become better adapted to human airways, though there is no evidence it has spread beyond the individual,

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.