Bird flu viruses dodge the human body’s fever defense

Recent research from the University of Cambridge has uncovered why fever is less effective against avian influenza viruses compared to human influenza viruses. The study identified a viral gene that influences the heat tolerance of flu viruses, revealing that many bird-origin viruses can continue to replicate at temperatures that inhibit human flu replication.

Seasonal human influenza A viruses usually prefer cooler temperatures within the upper respiratory tract, while avian influenza viruses thrive at higher temperatures found in their natural hosts – birds. The researchers utilized mouse models to simulate fever and found that a modest increase in temperature transformed lethal human flu infections into milder cases, whereas avian strains persisted even at elevated temperatures.

One significant finding was the role of the PB1 gene. Avian-like PB1 genes increased the virus’s resilience to heat, while human-like PB1 genes reduced it. This knowledge is crucial for understanding the evolution of influenza viruses, especially in the context of co-infection of various hosts like pigs, where gene segments can interchange.

The researchers stress the importance of monitoring bird flu strains for potential outbreaks and propose adding fever-resilience testing to existing protocols. Notably, while bird-to-human transmission is rare, notable human cases still arise, emphasizing the need for ongoing surveillance given the historically high fatality rates seen with certain avian strains.