San Antonio, TX — Researchers at the Texas Biomedical Research Institute (Texas Biomed) have identified nine critical mutations in an H5N1 bird flu strain isolated from a human in Texas. These mutations, absent in similar strains from bovine hosts, appear to enhance the virus’s ability to replicate in human cells and cause severe disease, including heightened replication in brain tissue in laboratory models.
Despite these alarming findings, current FDA-approved antiviral treatments remain effective against the strain, providing a key line of defense as researchers work to prevent a potential pandemic.
Alarming Mutation Patterns
The study, published in Emerging Microbes & Infections, compared the human-infecting strain with a similar strain found in dairy cattle. The human strain demonstrated significantly greater replication efficiency and pathogenicity in mouse models, underscoring the risk of the virus adapting further in human hosts.
“The clock is ticking for the virus to evolve to more easily infect and potentially transmit from human to human, which would be a serious concern,” said Dr. Luis Martinez-Sobrido, a professor at Texas Biomed and senior author of the study.
Antiviral Treatments Hold Firm
Encouragingly, testing revealed that the mutations did not alter the virus’s susceptibility to FDA-approved antiviral medications, offering a glimmer of hope.
“Antivirals will be a crucial tool in containing the spread of H5N1 until effective vaccines are developed,” noted Dr. Ahmed Mostafa Elsayed, the study’s lead author.
Broader Context and Next Steps
The ongoing H5N1 outbreak has affected a wide range of species, including wild birds, mammals, and for the first time, dairy cattle. Human infections, mostly among farm workers, have remained rare and typically mild, though the first U.S. death from H5N1 was reported in January 2025.
Texas Biomed researchers are now delving deeper into the mutations to identify the factors driving increased virulence. Their findings will inform strategies to mitigate the risk of cross-species transmission and limit opportunities for the virus to adapt to human hosts.
In a related study published in mBio, the team called for a “One Health” approach to eradicate H5N1 from dairy cattle and other mammals.
“Measures like enhanced decontamination protocols and stricter quarantine practices for livestock could significantly reduce the risk of mutations and cross-species infections,” said Dr. Elsayed.
Urgent Need for Vigilance
As H5N1 continues to circulate in the U.S., researchers emphasize the importance of surveillance, vaccination development, and antiviral stockpiling to address the growing threat.
For more information, read the full studies in Emerging Microbes & Infections and mBio.
References
- Mostafa, A., et al. “Replication kinetics, pathogenicity, and virus-induced cellular responses of cattle-origin influenza A(H5N1) isolates from Texas, United States.” Emerging Microbes & Infections, January 8, 2025. DOI: 10.1080/22221751.2024.2447614
- Mostafa, A., et al. “Avian influenza A (H5N1) virus in dairy cattle: origin, evolution, and cross-species transmission.” mBio, November 13, 2024. DOI: 10.1128/mbio.02542-24
- Sanz-Muñoz, I., et al. “Are we serologically prepared against an avian influenza pandemic and could seasonal flu vaccines help us?” mBio, December 31, 2024. DOI: 10.1128/mbio.03721-24
