The U.S. Centers for Disease Control and Prevention (CDC) discovered mutations in bird flu samples taken from a man in Louisiana.
The man’s illness marked the “first instance of severe illness linked to the virus in the United States,” the CDC said on December 18.
In a December 26 update, the CDC said it “identified low frequency mutations in the hemagglutinin gene of a sample sequenced from the patient, which were not found in virus sequences from poultry samples collected on the patient’s property, suggesting the changes emerged in the patient after infection.”
“Although concerning, and a reminder that A(H5N1) viruses can develop changes during the clinical course of a human infection, these changes would be more concerning if found in animal hosts or in early stages of infection (e.g., within a few days of symptom onset) when these changes might be more likely to facilitate spread to close contacts,” the statement added.
The CDC noted that the virus has not been reported to have been transmitted from the Louisiana patient to others.
This week, an adult in Los Angeles County was confirmed as having the area’s first human case of bird flu.
“The Los Angeles County Department of Public Health has confirmed a human case of H5 bird flu in an adult who was exposed to livestock infected with H5 Bird flu at a worksite,” the health department said in a statement. “This is the first human case of H5 bird flu detected in LA County. The person had mild symptoms, has been treated with antivirals, and is recovering at home. The overall risk of H5 bird flu to the public remains low.”
According to the health department, there is no evidence of person-to-person spread.