Last Updated:
Health experts said while the new finding is concerning, it is not a cause for alarm as the virus has been causing sporadic, mostly mild illnesses in people, and nearly all infected worked on dairy or poultry farms
A colourised transmission electron micrograph of avian influenza A H5N1 virus particles (in blue). (Image: National Institute of Allergy and Infectious Diseases/AFP)
Known to be causing cat infections across the United States, the bird flu virus has mutated inside a patient in Louisiana who contracted the country’s first severe case of the illness. This week, the CDC said the new development surfaced after a genetic analysis of a person older than 65 years.
According to the US Centres for Disease Control and Prevention (CDC), the person was hospitalised in critical condition with severe respiratory symptoms from bird flu after coming in contact with sick and dead birds in a backyard flock. Earlier this month, officials said the patient had not yet been identified and has underlying medical problems.
But, what does this new finding mean?
WHAT DOES THE ANALYSIS SHOW?
According to a report published by AFP, the genetic analysis showed that a small percentage of the H5N1 bird flu virus in the patient’s throat carried genetic changes that could increase its ability to bind to certain cell receptors found in the human upper respiratory tract.
The CDC, however, noted that these changes have not been detected in birds, including in the backyard poultry flock believed to have been the source of the initial infection. Instead, it 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 humans had been identified.
WHAT HAPPENS IF THE VIRUS MUTATES?
A report published by The Associated Press said scientists believe the mutations may allow the virus to better bind to receptors in the upper airways of humans. Michael Osterholm, a University of Minnesota infectious disease researcher, likened this binding interaction to a lock and key.
To enter a cell, the virus needs to have a key that turns the lock, and this finding means the virus may be changing to have a key that might work. “Is this an indication that we may be closer to seeing a readily transmitted virus between people? No,” Osterholm said. “Right now, this is a key that sits in the lock, but it doesn’t open the door.”
IS THIS MUTATION A CAUSE FOR ALARM?
Experts said while the new finding is concerning, it is not a cause for alarm. The virus has been causing sporadic, mostly mild illnesses in people in the US, and nearly all of those infected worked on dairy or poultry farms.
The CDC stressed there has been no known transmission of the virus from the Louisiana patient to anyone else. The agency said its findings about the mutations were “concerning”, but the risk to the general public from the outbreak “has not changed and remains low”.
Osterholm, however, said scientists should continue to follow what is happening with mutations carefully. “There will be additional influenza pandemics and they could be much worse than we saw with Covid,” he said. “We know that the pandemic clock is ticking. We just don’t know what time it is.”
Angela Rasmussen, a virologist at the University of Saskatchewan in Canada, told AFP while the mutation might help the virus enter cells more easily, additional evidence – such as animal testing – will be needed to confirm any effect on transmissibility.
Moreover, similar mutations have occurred in previous critically ill patients without leading to broader outbreaks. “It’s good to know we should be looking out for this,” Rasmussen said, adding, “but it doesn’t actually tell us, ‘Oh, we’re this much closer to a pandemic now.'”
Thijs Kuiken of 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 people,” he said, adding that the process is just one among several steps required for successful viral replication.
Kuiken pointed out that rather than intensifying disease, such adaptations might actually result in milder infections by favouring cells in the upper respiratory tract – causing symptoms like a runny nose or sore throat – rather than affecting the lower respiratory tract, which leads to more severe pneumonia.
WHAT CAN HAPPEN NEXT?
The ongoing spread of bird flu in the US has alarmed experts, who warned that the country is not reacting fast enough to the threat; this, despite the discovery of the new mutation coupled with rising cat infections.
But, several experts contacted by AFP cautioned that it was too early to determine if these changes will make the virus more transmissible or more severe in people. They, however, expressed bigger concerns about the sheer volume of bird flu circulating at present.
The CDC has reported 65 confirmed human cases in 2024, and many more may go undetected among dairy and poultry workers. Rasmussen warned that this widespread circulation increases the likelihood of the virus mixing with seasonal influenza, potentially triggering “rapid evolutionary leaps”, similar to events that caused the 1918 and 2009 flu pandemics.
WHAT DO WE KNOW ABOUT CAT INFECTIONS?
Researchers are also keeping a close eye on the mounting cases of bird flu infections in cats. A cat in Oregon died after consuming raw pet food confirmed to be contaminated with H5N1. “This cat was strictly an indoor cat; it was not exposed to the virus in its environment,” said state veterinarian Ryan Scholz in a statement.
Genome sequencing showed that the virus in the pet food matched exactly the strain found in the cat. In Washington State, 20 big cats at a sanctuary also died recently after contracting bird flu, the Wild Felid Advocacy Center of Washington wrote on Facebook.
Rasmussen said infected outdoor cats could 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 said, adding, “and that cat comes back into your house and you’re snuggling with it, you’re sleeping with it… that creates additional exposure risk.”
(With agency inputs)
- Location :
Washington D.C., United States of America (USA)