A warning has been issued by experts that the virus behind the rise in bird flu cases globally is quickly changing. This has led to calls for the vaccination of poultry in countries that have been affected.
While the risk to humans is still low, there is growing concern over the increasing number of cases of bird flu cases in mammals.
Up until the middle of 2021, the H5N1 bird flu virus had mainly caused outbreaks during certain seasons. However, something shifted at that point, causing the group of viruses to become much more infectious, says Richard Webby, who leads a World Health Organization (WHO) center that studies animal flu.
Since then, outbreaks have been happening all year round and have spread to new areas, resulting in the deaths of many wild birds and the culling of millions of poultry.
Webby, who works at St Jude Children’s Research Hospital in Memphis, says this is the biggest outbreak of bird flu the world has ever seen.
When the virus arrived in North America it became more virulent and caused more severe illness. In one experiment, a ferret was infected with one of the new strains of bird flu and was found to have a very high concentration of the virus in its brain. This suggests that it is more pathogenic than earlier strains.
Webby stresses that although the risk to humans is still low, the virus is constantly changing and could develop traits that make it easier to transmit to humans.
It is rare for humans to become infected with bird flu and this usually happens after close contact with infected birds. However, there are now more cases of the virus being found in mammals and Webby finds this very worrying.
Webby explains that bird viruses attach to different receptors on host cells than human viruses do. But with just a few small changes to one viral protein, the virus could become better adapted to humans.