New bird flu mutation discovered in US as cat infections cause alarm

The continued spread of bird flu in the United States has alarmed experts — not only because of human cases causing serious illness, but also because of disturbing new cases of infections in cats.

A sample of the virus found in a critically ill patient in the United States shows signs of mutating to better match the human respiratory tract, although there is no evidence it has spread beyond that person, authorities report.

Earlier this month, officials announced that an elderly Louisiana patient was in “critical condition” with a severe H5N1 infection.

An analysis from the Centers for Disease Control and Prevention (CDC) on Thursday found that a small percentage of the virus in the patient’s throat carried genetic changes that compromised the virus’s ability to bind to certain cell receptors in the upper human airways could enlarge.

Importantly, the CDC noted that these changes have not been observed in birds — including the backyard poultry flock that is believed to have been the source of the patient’s initial infection.

Instead, the agency said the mutations were “likely generated by replication of this virus in the patient with advanced disease,” stressing that no transmission of the mutated strain to other people had been identified.

Several experts contacted by AFP cautioned that it was too early to determine whether these changes would make the virus more transmissible or more severe in humans.

Angela Rasmussen, a virologist at the University of Saskatchewan in Canada, explained that while the mutation could help the virus enter cells more easily, additional evidence – such as animal testing – would be needed to confirm any effect on transmissibility.

Furthermore, similar mutations have occurred in previous critically ill patients without leading to wider outbreaks.

“It’s good to know that we need to pay attention to this,” Rasmussen said, “but it doesn’t really tell us, ‘Oh, we’re much closer to a pandemic now.’”

Thijs Kuiken of the Erasmus University Medical Center in the Netherlands agreed.

“Efficient attachment to human upper respiratory tract cells is necessary, but not sufficient, for more efficient transmissibility between humans,” he said, adding that the process is just one of many steps required for successful viral replication.

Rather than intensifying the disease, Kuiken points out, such adjustments could actually result in milder infections by favoring cells in the upper respiratory tract – which causes symptoms such as a runny nose or sore throat – rather than affecting the lower respiratory tract, which leads to leads to more serious pneumonia. .

‘Fast evolutionary leaps’ possible

Rasmussen expressed greater concern about the enormous amount of bird flu currently circulating.

The CDC has reported 65 confirmed human cases in 2024, and many more may go undetected among dairy and poultry workers.

This widespread spread, Rasmussen warned, increases the chance that the virus will mix with seasonal flu, potentially leading to “rapid evolutionary leaps” similar to events that caused the 1918 and 2009 flu pandemics.

Researchers are also closely monitoring rising cases of bird flu infections in cats.

A cat in Oregon died after eating raw pet food confirmed to be contaminated with H5N1, prompting a recall of Northwest Naturals’ Feline Turkey Recipe raw and frozen pet food.

“This cat was purely an indoor cat; he was not exposed to the virus in his environment,” state veterinarian Ryan Scholz said in a statement. Genome sequencing showed that the virus in the pet food exactly matched the strain found in the cat.

In Washington state, 20 big cats also recently died at a shelter after contracting bird flu, the Wild Felid Advocacy Center of Washington wrote on Facebook.

Rasmussen warns that infected outdoor cats can return home and expose people to the virus through close contact.

“If you have an outdoor cat that gets H5 from eating a dead bird,” she explained, “and that cat comes back into your house and you cuddle with it, you sleep with it… that creates additional exposure risk.”

© 2024 AFP