With the persistent spread of the H5N1 avian influenza, the scientific community is diligently striving to understand the implications of this virus on human health. Alarmingly, this virus has been detected in the milk of dairy cows, thereby infecting those working on farms. This has prompted a comprehensive study by researchers at St. Jude Children’s Research Hospital, aiming to develop potential antidotes for this deadly virus. However, their findings, which have been recently published in Nature Microbiology, reveal that current FDA-approved flu antivirals have limited efficacy in treating serious H5N1 infections.
The study further highlighted the significant role of the infection route, whether it be through the eye, nose, or mouth, in determining the effectiveness of the treatment. Richard Webby, PhD, from the St. Jude Department of Host-Microbe Interactions, expressed his concerns about the difficulty of treating severe infections caused by this particular H5N1 strain found in cows. He emphasized the importance of preventive measures such as avoiding the consumption of raw milk and minimizing exposure among dairy farm workers.
Although H5N1 infections in humans are relatively uncommon, the ongoing outbreak has infected over 60 people through exposure to dairy products. The infection was typically contracted through contact with contaminated raw cow’s milk, often affecting dairy workers when splashes or aerosolized particles reached their eyes or noses.
To understand the effects of different antiviral drugs against the virus, the St. Jude team employed a mouse model to test the drugs’ efficacy via three distinct exposure routes. Jeremy Jones, PhD, also from St. Jude Department of Host-Microbe Interactions, revealed that while baloxavir (Xofluza) was generally more effective in reducing viral levels than oseltamivir (Tamiflu), neither drug was consistently successful in treating the infection.
Among the three exposure routes studied, namely the eye, mouth, and nose, the oral route proved to be most problematic. This is because the virus extended beyond the lungs to the brain and bloodstream when contracted orally, mimicking the consumption of contaminated raw cow’s milk. The antivirals were unable to prevent it or improve survival outcomes.
However, the study did reveal that baloxavir was effective in controlling infections contracted through the eyes. This finding is particularly noteworthy considering that eye exposure is a common infection route for those in close contact with dairy cows. Baloxavir demonstrated a 100% survival rate against eye infections, while oseltamivir showed a 25% survival rate.
The nasal route showed mixed results. While baloxavir was more successful in reducing viral levels than oseltamivir, the virus managed to infiltrate the brain. However, both antivirals were able to increase survival rates, with baloxavir and oseltamivir achieving 75% and 50% survival rates respectively.
In conclusion, the effectiveness of current antivirals against the H5N1 bird flu is significantly influenced by both the route of infection and the specific drug used. In light of these findings, Richard Webby insists on the urgency of exploring alternative drug combinations and dosages, while focusing on reducing infection risks as the primary method of protecting against this threatening virus.
This pivotal study was supported by grants from the National Institute of Allergy and Infectious Diseases and ALSAC, the fundraising and awareness organization of St. Jude. Other contributors to the study include Konstantin Andreev, Thomas Fabrizio and Elena Govorkova from St. Jude, and Andrew Bowman from The Ohio State University.
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