The Louisiana patient who contracted what officials said was the nation’s first “severe” case of avian influenza has died, the state health department said Monday. The person who contracted the H5N1 strain of highly pathogenic bird flu in southwest Louisiana had been hospitalized since mid-December.

The patient, who was older than 65 and had underlying medical conditions, was hospitalized weeks ago in critical condition with severe respiratory illness.

The first Louisiana patient with bird flu has died, officials with the state health department said Monday. The death is the first U.S. H5N1-related human death, the agency said.