Mutations Detected in First Severe Human Bird Flu Case in the U.S.: What It Means

In a recent development, the U.S. Centers for Disease Control and Prevention (CDC) revealed that the first severe case of bird flu in the U.S. involves mutations not previously observed in samples from an infected backyard flock on the patient’s property. The patient, a 65-year-old from Louisiana suffering from severe respiratory illness, showed mutations in the hemagglutinin (HA) gene, which plays a crucial role in the virus attaching to host cells. Additionally, one of these mutations was also found in a bird flu virus sample taken from a teenager in British Columbia, who was in critical condition at a Vancouver hospital.

The identified mutations are thought to enhance the ability of the H5N1 virus to bind to cell receptors in the upper respiratory tract of humans. Normally, the bird flu virus attaches to a cell receptor that is uncommon in the human upper airways, which is why H5N1 does not easily infect people or spread from person to person.

The Louisiana patient was infected with the D1.1 genotype of the virus, which was recently found in wild birds and poultry in the US, rather than the B3.13 genotype seen in dairy cows, humans, and poultry across several states.

While the mutations observed in the patient are rare, they are not unprecedented and typically occur during severe infections. One of the mutations was also found in another severe case in British Columbia, Canada. The CDC has reassured that there has been no transmission of the virus from the patient to others.

The question remains: Will these mutations make bird flu more contagious or dangerous to humans?

Will these mutations make bird flu more contagious?

The mutations found in the patient’s samples were not present in the virus from the birds, indicating that these changes developed during the person’s infection. According to Scott Hensley, a microbiology professor at the University of Pennsylvania, it would have been more alarming if the mutations had been found in the virus from the birds, as it would suggest that the virus in nature was acquiring these changes.

Virologist Angela Rasmussen noted on X (formerly Twitter) that the trend of increasing human infections must be reversed, as each new case provides an opportunity for the virus to evolve. She emphasized, “We don’t know what combination of mutations could lead to a pandemic strain of H5N1, and while predictions can be made from genetic data, the more humans infected, the higher the chances for a pandemic virus to emerge.”