Chicken flu viruses current a major danger to people as a result of they’ll proceed replicating at temperatures greater than a typical fever. Fever is without doubt one of the physique’s principal instruments for slowing or stopping viral infections, but analysis led by the colleges of Cambridge and Glasgow exhibits that avian flu strains can preserve multiplying even when the physique reaches temperatures that usually hinder viruses.
In a research printed in Science, the researchers recognized a gene that strongly influences how delicate a flu virus is to warmth. Through the main pandemics of 1957 and 1968, this gene moved into human flu viruses, and the ensuing strains have been in a position to unfold effectively.
Why Temperature Issues for Flu Viruses
Human flu viruses infect thousands and thousands of individuals yearly, with influenza A being the commonest seasonal pressure. These viruses replicate most successfully within the higher respiratory tract, the place temperatures are round 33 °C. They replicate much less effectively deeper within the lungs, the place temperatures rise to about 37 °C.
If left uncontrolled, viruses unfold via the physique and should trigger extreme sickness. Fever is without doubt one of the physique’s protecting responses and might elevate core temperature to as excessive as 41 °C. Till not too long ago, nevertheless, it remained unclear precisely how fever limits viral development, or why some viruses can proceed thriving regardless of it.
Avian Flu Thrives in Hotter Environments
Avian influenza viruses behave in another way from human flu strains. They typically develop within the decrease respiratory tract, and of their ordinary hosts, together with geese and seagulls, they steadily infect the intestine. These environments can attain temperatures of 40 to 42 °C.
Previous laboratory research utilizing cultured cells confirmed that avian flu viruses have a tendency to resist temperatures much like these seen throughout fever in people. The brand new analysis turns to in vivo fashions, utilizing mice contaminated with influenza viruses, to raised perceive how fever protects the physique and why this safety might not be sufficient in opposition to chook flu.
Simulating Fever in Mice
The worldwide crew led by scientists in Cambridge and Glasgow created fever-like situations in mice to watch how totally different flu strains responded. Their experiments used a laboratory-adapted human-origin influenza virus often known as PR8, which isn’t a hazard to people.
Mice don’t normally develop fever in response to influenza A viruses, so the crew mimicked fever by elevating the temperature of the surroundings the place the mice lived (elevating the physique temperature of the mice).
Human Flu Stops at Excessive Warmth, Avian Flu Does Not
The findings confirmed that rising physique temperature to fever ranges successfully stopped human-origin flu viruses from replicating. This identical temperature improve didn’t cease avian flu viruses. For human flu strains, elevating the temperature by simply 2 °C was sufficient to show what would have been a deadly an infection into a light one.
A Key Gene Behind Chicken Flu’s Warmth Resistance
The research additionally discovered that the PB1 gene, which helps viral genome replication inside contaminated cells, performs a significant function in figuring out temperature sensitivity. Viruses with an avian-like PB1 gene tolerated fever-associated temperatures and prompted extreme sickness in mice. This issues as a result of human and chook flu viruses can trade genes after they infect the identical host, similar to pigs, on the identical time.
Dr. Matt Turnbull, first writer of the research from the Medical Analysis Council Centre for Virus Analysis on the College of Glasgow, mentioned: “The flexibility of viruses to swap genes is a continued supply of risk for rising flu viruses. We have seen it occur earlier than throughout earlier pandemics, similar to in 1957 and 1968, the place a human virus swapped its PB1 gene with that from an avian pressure. This will assist clarify why these pandemics prompted critical sickness in individuals.
“It is essential that we monitor chook flu strains to assist us put together for potential outbreaks. Testing potential spillover viruses for a way resistant they’re prone to be to fever might assist us establish extra virulent strains.”
Excessive Fatality Charges Spotlight the Hazard
Senior writer Professor Sam Wilson, from the Cambridge Institute of Therapeutic Immunology and Infectious Illness on the College of Cambridge, mentioned: “Fortunately, people do not are inclined to get contaminated by chook flu viruses very steadily, however we nonetheless see dozens of human circumstances a 12 months. Chicken flu fatality charges in people have historically been worryingly excessive, similar to in historic H5N1 infections that prompted greater than 40% mortality.
“Understanding what makes chook flu viruses trigger critical sickness in people is essential for surveillance and pandemic preparedness efforts. That is particularly vital due to the pandemic risk posed by avian H5N1 viruses.”
Implications for Remedy
Reference: “Avian-origin influenza A viruses tolerate elevated pyrexic temperatures in mammals” by Matthew L. Turnbull, Yingxue Wang, Simon Clare, Gauthier Lieber, Stephanie L. Williams, Marko Noerenberg, Akira J. T. Alexander, Sara Clohisey Hendry, Douglas G. Stewart, Joseph Hughes, Simon Swingler, Spyros Lytras, Emma L. Davies, Katherine Harcourt, Katherine Smollett, Rute M. Pinto, Hui-Min Lee, Eleanor R. Gaunt, Colin Loney, Johanna S. Jung, Paul A. Lyons, Darrell R. Kapczynski, Edward Hutchinson, Ana da Silva Filipe, Jeffery Okay. Taubenberger, Suzannah J. Rihn, J. Kenneth Baillie, Ervin Fodor, Alfredo Castello, Kenneth G. C. Smith, Paul Digard and Sam J. Wilson, 27 November 2025, Science.
DOI: 10.1126/science.adq4691
The analysis was funded primarily by the Medical Analysis Council, with extra funding from the Wellcome Belief, Biotechnology and Organic Sciences Analysis Council, European Analysis Council, European Union Horizon 2020, UK Division for Surroundings, Meals & Rural Affairs, and US Division of Agriculture.
