As the H5N1 bird flu virus is spreading fast among animals in the United States, scientists are now on high alert for signs of human-to-human transmission. According to new research, the virus might require only one mutation to be able to transmit between humans.
H5N1 is a highly deadly virus, killing 50% of humans who become infected. Experts believe that closely monitoring animal infections is necessary to control the virus, halt its mutation, and prevent it from directly infecting people, thereby preventing a global outbreak.
Normally, bird flu needs several mutations to be a threat to humans. However, scientists at the Scripps Research Institute in California suggest that this time, the virus could adapt faster, raising concerns about the possibility of a pandemic.
The findings-published in Journal Science on December 5, 2024-highlight the need to monitor H5N1’s evolution.
As per a release by Scripps Research Institute, currently, there are no documented cases of H5N1 transmitting between people: bird flu cases in humans have been linked to close contact with contaminated environments as well as infected birds (including poultry), dairy cows, and other animals. However, public health officials are concerned about the potential for the virus to evolve to transmit efficiently between humans, which could lead to a new, potentially deadly pandemic.
The flu virus attaches to its host via a protein called hemagglutinin that binds to glycan receptors on the surfaces of host cells. Glycans are chains of sugar molecules on cell surface proteins that can act as binding sites for some viruses. Avian (bird) influenza viruses like H5N1 primarily infect hosts with sialic acid-containing glycan receptors found in birds (avian-type receptors). While the viruses rarely adapt to humans, if they evolve to recognise sialylated glycan receptors found in people (human-type receptors), they could gain the ability to infect and possibly transmit between humans.
“Monitoring changes in receptor specificity (the way a virus recognises host cells) is crucial because receptor binding is a key step toward transmissibility,” says Ian Wilson, DPhil, co-senior author and the Hansen Professor of Structural Biology at Scripps Research. “That being said, receptor mutations alone don’t guarantee that the virus will transmit between humans.”
“The findings demonstrate how easily this virus could evolve to recognise human-type receptors,” says first author Ting-Hui Lin, a postdoctoral associate at Scripps Research. “However, our study doesn’t suggest that such evolution has occurred or that the current H5N1 virus with only this mutation would be transmissible between humans.”
