A recent study conducted by researchers at the University of Glasgow has found that mutations that could potentially allow bird flu viruses to cross over to humans are present in many strains of the H5N1 virus currently causing outbreaks in wild birds. However, these genetic changes would still need further mutations to cause a pandemic in humans.
The researchers discovered a human immune system protein called butyrophilin that typically plays a role in preventing bird flu from infecting humans. In past flu pandemics, the viruses had genes that allowed them to overcome this antiviral protein. While these mutations alone are not enough to cause a pandemic, scientists believe that the fewer mutations present, the better.
The current bird flu outbreak, specifically the H5N1 subtype, has been circulating in large numbers among wild birds since 2021 and has caused significant die-offs of threatened species. It has also affected farmed poultry and mammals that prey on birds, with a few cases reported in humans. However, the virus has not yet evolved the ability to easily spread between mammals, which is of great interest to researchers.
The study found that the human form of butyrophilin, which evolved about 40 million years ago, is effective at stopping most bird flu viruses from reproducing. However, mutations similar to those seen in the 1918 flu pandemic, which crossed over to humans from birds, have been observed in about half of the H5N1 viruses causing the current outbreak in wild birds and in nearly all cases that occurred in humans.
Despite these mutations, there has been no widespread transmission of the virus among humans. Scientists believe that further mutations or gene swapping with other viruses would likely be necessary for that to occur. It is reassuring to note that the current H5N1 viruses do not seem to spread easily to humans, according to a report from the UK Health Security Agency.
Researchers are actively monitoring for the presence of mutations that would allow these viruses to overcome butyrophilin. By understanding the potential barriers that the virus needs to overcome to spread to humans, scientists can better assess the risk and develop appropriate measures to prevent a pandemic.