New Study Reveals Transmissibility of Bovine H5N1 Influenza in Animal Models
A recent study published in the journal Nature has uncovered alarming findings regarding a highly pathogenic avian influenza (HPAI) H5N1 virus. This particular strain, known as huTX37-H5N1, was isolated from a farm worker who contracted the virus through contact with infected dairy cows. The research highlights the virus’s lethal potential and its ability to be transmitted between animals, raising concerns for public health officials.
The investigation revealed that the huTX37-H5N1 virus was lethal in laboratory models, specifically in mice and ferrets. The infected worker experienced mild symptoms, including conjunctivitis, but the implications of the virus’s transmissibility are significant. Researchers found that the virus could be transmitted through the air between ferrets housed in separate cages, suggesting that airborne transmission may be possible.
One of the critical mutations identified in the huTX37-H5N1 strain is PB2-E627K, which is commonly found in avian influenza viruses that can replicate efficiently in mammals. This mutation raises alarms about the potential for the virus to adapt further and pose a greater threat to human health. The findings underscore the importance of ongoing monitoring of H5N1 viruses, especially in light of the current outbreak.
In addition to its lethal nature, the study also assessed the susceptibility of the bovine H5N1 virus to various antiviral medications. The researchers found that the virus was highly susceptible to favipiravir and baloxavir marboxil (known as Xofluza), both of which belong to the polymerase inhibitor class. Additionally, the neuraminidase inhibitor zanamivir was effective against the virus. However, the virus showed reduced sensitivity to oseltamivir (Tamiflu), which is commonly used to treat influenza.
Laboratory tests demonstrated that huTX37-H5N1 was capable of replicating in human cornea and lung cells, further indicating its potential threat to human health. The lethal dose of huTX37-H5N1 was found to be less than 1 plaque-forming unit (PFU) in mice, significantly lower than the 31.6 PFU lethal dose observed in a bovine H5N1 virus isolated from the milk of a lactating cow. The study also revealed that huTX37-H5N1 infected all 15 different mouse tissues tested, with the highest viral loads detected in respiratory tissues.
To further explore the virus’s impact on respiratory transmission, researchers conducted experiments with ferrets, which are known to model human flu infections more closely than mice. In these experiments, all ferrets infected with a high dose of huTX37-H5N1 succumbed within five days. The virus was detected in all sampled tissues, with particularly high levels found in the respiratory system, indicating a severe and rapid progression of the disease.
In prior studies, researchers had infected ferrets with a different strain of bovine H5N1, which, while causing severe illness, did not lead to the same level of lethality observed with huTX37-H5N1. This stark difference in outcomes emphasizes the potential dangers posed by this newly identified strain.
The findings from this study have significant implications for public health and biosecurity. As H5N1 viruses continue to circulate among avian and mammalian populations, the risk of transmission to humans remains a critical concern. Health officials are urged to enhance surveillance efforts and develop strategies to mitigate the risks associated with this and other emerging influenza viruses.
As the scientific community continues to investigate the complexities of H5N1 and its potential impact on human health, it becomes increasingly important to remain vigilant and prepared for any developments that may arise from this ongoing situation.
