A concerning discovery from Scripps Research reveals that a single genetic change in the current H5N1 influenza virus affecting U.S. dairy cows could make it easier for the virus to infect humans. While the current risk to humans remains low, the finding emphasizes the importance of continued surveillance.
Published in Science | Estimated reading time: 4 minutes
The highly pathogenic avian influenza (HPAI) H5N1 virus, which has spread through U.S. dairy farms in 2024, could potentially become more dangerous to humans through a single mutation in its surface protein. Researchers at Scripps Research found that changing just one amino acid in the virus’s hemagglutinin protein could switch its preference from bird-type to human-type cellular receptors.
The study analyzed the H5N1 strain from the first U.S. human infection with the bovine strain in Texas. “Although there are currently no documented cases of transmission between humans, there is concern that the virus could adapt for human-to-human transmission and potentially result in an influenza pandemic,” the researchers note in their paper.
The critical mutation, known as Q226L (changing glutamine to leucine at position 226), completely altered the virus’s ability to attach to human cells. This modification could represent a crucial step toward the virus becoming more transmissible among humans, though additional changes would likely be needed for a pandemic to occur.
Key Findings
The research team, led by Ting-Hui Lin and colleagues, discovered that while the current H5N1 virus strongly prefers binding to avian-type receptors, the Q226L mutation dramatically switches this preference to human-type receptors. This finding is particularly significant because previous studies of H5N1 typically required multiple mutations to achieve similar effects.
The virus has already infected at least 15 people worldwide with the 2.3.4.4b variant as of October 2024, including cases from exposure to infected cows and poultry. While current infections have been mild, historical H5N1 infections have resulted in much more severe outcomes.
Glossary
- Hemagglutinin (HA)
- A protein on the surface of influenza viruses that allows them to attach to and infect cells
- Receptor Specificity
- The ability of a virus to recognize and bind to specific types of molecules on cell surfaces
- Mutation
- A change in genetic material that can alter the properties of an organism or virus
Test Your Knowledge
What is the specific mutation that could make H5N1 better at infecting human cells?
The Q226L mutation, which changes glutamine to leucine at position 226 in the hemagglutinin protein.
Why is the current H5N1 virus primarily affecting birds and not humans?
Because its hemagglutinin protein prefers binding to avian-type receptors, which are not common in the human upper respiratory tract.
How many mutations were typically needed in previous H5N1 strains to switch receptor preference?
Previous studies found that three or more mutations were usually required to switch receptor preference from avian to human type.
What makes this particular finding concerning from a public health perspective?
The fact that only a single mutation is needed dramatically increases the likelihood of the virus achieving this change, compared to requiring multiple simultaneous mutations.
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