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As the H5N1 avian influenza virus continues to pose a significant challenge, researchers are racing to gauge its implications for human health. Recent findings reveal the presence of the virus in cow’s milk and document instances of infection among agricultural workers. In light of these developments, experts from St. Jude Children’s Research Hospital are investigating potential treatment options. Their research, which has been published in Nature Microbiology, indicates that commonly used antiviral medications for influenza may not effectively combat severe H5N1 infections.
According to Richard Webby, PhD, a leading researcher in the study, “Our evidence suggests that treating individuals severely affected by this bovine H5N1 strain is likely to be challenging. Therefore, preventing infection—such as avoiding raw milk consumption and minimizing exposure for dairy farm staff—may prove to be more effective strategies.”
Limitations of Existing Antivirals
While human infections with H5N1 are infrequent, current statistics show that over 60 individuals have contracted the virus due to exposure during this outbreak. Infections have typically occurred through contact with raw, contaminated cow’s milk, often as a result of splashes or airborne particles reaching the nasal or ocular regions. To assess the efficacy of various antiviral drugs, researchers utilized a mouse model to analyze how these medications responded against the virus through three different routes of exposure.
“Overall, baloxavir [Xofluza] demonstrated a stronger reduction in viral levels compared to oseltamivir [Tamiflu], although neither drug proved consistently effective,” noted Jeremy Jones, PhD, who led the research.
The study focused on transmission pathways, including ocular, oral, and nasal routes, to understand how each correlated with infection rates. Notably, the oral route, which simulates the ingestion of infected cow’s milk, resulted in the most severe infections and presented significant treatment challenges.
“Oral transmission allowed the virus to spread well beyond the lungs,” Webby explained. “It extended its reach to the brain and bloodstream, with antiviral treatments failing to halt progression or improve survival rates.”
Results from the study revealed that baloxavir was particularly effective for infections contracted through the eye, showing promising implications for dairy workers who might be exposed to this route.
“In cases of ocular infection, baloxavir led to a survival rate of 100%, compared to just 25% with oseltamivir,” Jones stated. “This reinforces the potential advantages of baloxavir when the virus is introduced through the eye.”
When examining the nasal exposure route, findings were less definitive. Baloxavir did perform better than oseltamivir in reducing viral levels; however, the virus was still able to reach the brain. In terms of survival rates, both antivirals showed some efficacy, achieving 75% survival with baloxavir and 50% with oseltamivir.
“Our research reveals that the efficacy of existing antiviral drugs against H5N1 is dependent on both the route of infection and the specific drug used, with some treatments appearing nearly ineffective,” Webby noted. “As we continue to investigate potential drug combinations and dosages, it’s imperative that we prioritize measures to minimize infection risks, as this is currently the most viable strategy to safeguard public health against this virus.”
Contributors and Funding Sources
The research was conducted by a collaborative team including Konstantin Andreev, Thomas Fabrizio, and Elena Govorkova from St. Jude, along with Andrew Bowman from The Ohio State University. The study received financial backing from the National Institute of Allergy and Infectious Diseases (contract #75N93021C00016) and ALSAC, the fundraising arm of St. Jude.
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