The Centers for Disease Control and Prevention (CDC) is closely monitoring potential warning signs related to the spread of bird flu in the United States, particularly focusing on any indications that the virus could evolve into a pandemic. As of the CDC's last update before the holiday break, there have been 66 confirmed human cases of bird flu nationwide. Updates will resume on January 3rd.

A key concern for the CDC is identifying any clusters of influenza A(H5N1) cases that might suggest increased human-to-human transmission. The agency is also analyzing circulating virus strains for genetic mutations that could enhance their ability to spread among people.

Specifically, the CDC is looking for outbreaks resulting from person-to-person spread and evidence of viral mutations, as reported by Newsweek. A recent case in Louisiana, where a hospitalized patient with severe bird flu was found to have a mutated version of the virus, raised concerns. According to the CDC, this patient's virus sample contained low-frequency mutations in the hemagglutinin gene, which were absent in poultry samples from the patient's property. This suggests the mutations developed after the patient contracted the infection.

This undated electron microscopic image shows two Influenza A (H5N1) virions, a type of bird flu virus. (Cynthia Goldsmith, Jackie Katz/CDC via AP, File)

While such mutations are uncommon in humans, the CDC notes they have been observed in prior H5N1 cases internationally, often in individuals with severe illness. The agency emphasized that there is no evidence of transmission from the Louisiana patient to others.

A recall alert is displayed after a batch of raw frozen pet food tested positive for bird flu. (Jenny Kane)

Avian influenza (HPAI) is highly contagious and can spread among bird flocks through contact with infected animals, contaminated equipment, or the clothing and footwear of handlers. Recent reports indicate the virus has spread to flocks in two more Michigan counties.

A cow at the state fair. Dairy farmers were taking precautions against avian flu. (Reuters/Jim Vondruska)

FILE PHOTO: A test tube labelled "Bird Flu". (REUTERS/Dado Ruvic/Illustration/File Photo)

The CDC maintains that the public health risk from avian influenza remains low and confirms that no infected birds or poultry products will enter the food supply.