Recent research has unveiled that bird flu viruses can replicate at temperatures higher than typical human fevers, presenting increased risks to human health. Normally, when individuals contract human-origin influenza A viruses, their body responds by raising its temperature, which effectively inhibits the virus's ability to replicate. In contrast, avian influenza viruses thrive in warmer conditions found in the lower respiratory tract of their natural hosts, such as ducks and seagulls, where temperatures can reach 40 to 42 degrees Celsius.

Studies conducted by researchers from Cambridge and Glasgow universities indicate that while fever can shield against milder human flu strains, it is less effective against bird flu. The research highlighted the potential threat avian H5N1 viruses pose to humans, given their historically high mortality rates, sometimes exceeding 40% in certain cases.

Professor Sam Wilson from the University of Cambridge emphasized the importance of understanding the factors that enable bird flu viruses to cause severe illness in humans. This knowledge is essential for enhancing surveillance and improving pandemic preparedness, especially in light of the persistent threat postulated by avian viruses.

To explore this issue, the study used in vivo models involving mice infected with adapted influenza viruses. While mice do not typically exhibit fever in response to such infections, researchers elevated the ambient temperature to simulate fever conditions and investigate the virus's behavior. Their findings indicated that strains of avian flu viruses, particularly those with an avian-like PB1 gene, demonstrated an ability to endure fever-like temperatures, which contributed to severe illness in the mice.

Ultimately, this research sheds light on the limitations of fever as a defense mechanism against avian influenza in humans. The implications of these findings are crucial for understanding potential risks and preparing for future outbreaks of bird flu in human populations.