Nikhil Prasad Fact checked by:Thailand Medical News Team Nov 28, 2025 1 hour ago
Medical News: New research from the University of Cambridge, the Cambridge Institute of Therapeutic Immunology and Infectious Disease, and the Medical Research Council Centre for Virus Research at the University of Glasgow has revealed troubling evidence that certain bird flu viruses possess an unusual and dangerous advantage over typical human influenza strains. Unlike common human flu viruses that slow down or die off when body temperature rises, avian influenza viruses can keep replicating even when the body mounts a strong fever. This surprising discovery, detailed in this
Medical News report, highlights why bird flu spillover infections continue to cause severe disease and why their pandemic potential remains one of the world’s biggest public-health concerns.
New research shows avian flu viruses can survive fever temperatures, raising the risk of severe human infections
Why Fever Normally Helps the Body Fight Flu
Seasonal human influenza A viruses prefer cooler temperatures, typically around 33°C, which is the temperature found in the upper respiratory tract. When infection spreads deeper into the lungs where temperatures increase to about 37°C, these human strains already lose some replicative efficiency. Fever, which can push body temperature above 40°C, usually slows down these viruses even further. For decades, scientists believed fever worked primarily by activating immune responses, but the Cambridge and Glasgow teams wanted to understand whether heat itself was directly antiviral.
Human fever can reach as high as 41°C during intense infection. For most human-adapted flu strains, this rise in body temperature is enough to halt viral replication, limiting spread and reducing the severity of disease. However, this natural defense mechanism appears far less effective against certain avian influenza viruses that originate in birds whose normal body temperature is already 40°C to 42°C.
How the New Study Was Conducted
Using a controlled mouse model, researchers simulated fever conditions by slightly raising the ambient temperature. They tested a human-origin laboratory influenza strain known as PR8, which replicates poorly at higher temperatures, and compared it with genetically engineered versions carrying specific avian influenza genes. Mice exposed to the human-origin virus became protected once their body temperature rose just 2°C, turning what should have been a deadly infection into a mild one.
But things changed dramatically when the virus carried the PB1 gene from avian influenza strains. This particular gene, which helps the virus replicate its genetic material, made the virus significantly more resistant to heat. Even under simulated fever, these avian-gene-carrying viruses replicated aggressively, causing severe disease in the mice. The PB1 gene has been previously implicated in the deadly 1957 and 1968 pandemics, during which human and bird flu viruses mixed and shared genetic segments, creating new temperature-resistant strains.
Why Avian Flu Viruses Pose
Such a High Risk
Birds naturally operate at higher body temperatures, especially in the gut where avian influenza typically replicates. Because these viruses are already heat-adapted, the normal human fever response offers little protection. This helps explain why avian influenza spillover infections—such as H5N1 cases with mortality rates exceeding 40 percent—can lead to severe disease even when the patient experiences high fever.
Experts from the University of Cambridge emphasize that although human infections with bird flu remain rare, dozens still occur globally each year. The genetic traits enabling avian viruses to remain stable in heat raise concerns about future pandemics, especially if widespread reassortment occurs in intermediate animals such as pigs, which can host both human and avian strains simultaneously.
Key Scientific Insights from the Study
The research clearly shows that:
• A rise of only 2°C in body temperature can protect against most human-origin flu viruses
• Avian-origin PB1 genes override this protective effect and allow rapid viral replication even at 40°C
• Past pandemics involved the acquisition of these PB1 genes
• Fever alone may not stop avian spillover viruses
• Suppressing fever with medications like aspirin or ibuprofen might unintentionally help certain influenza viruses replicate, though more research is required before treatment guidelines can change
Conclusion
This new study highlights a profound and worrying biological reality. Fever is one of the body’s oldest defenses against viral infection, yet bird flu viruses have evolved to thrive in conditions that would normally halt most pathogens. The ability of avian influenza strains to resist temperatures above 40°C means that a human fever, which should slow illness, may fail to stop viral replication. Even more concerning is that the PB1 gene responsible for this heat resistance has already jumped into human influenza viruses during past pandemics, causing substantial global illness. Understanding this mechanism is therefore essential for global surveillance, vaccine design, and pandemic preparedness. It underscores the urgent need to monitor bird flu strains circulating in animals and to study how risky gene swapping between human and avian viruses may create more dangerous variants. Without such vigilance, the world could face influenza outbreaks that natural human defenses, including fever, are unable to control.
The study findings were published in the peer reviewed journal: Science.
https://www.science.org/doi/10.1126/science.adq4691
For the latest on Avian Flu Viruses, keep on logging to Thailand
Medical News.
Read Also:
https://www.thailandmedical.news/articles/h5n1-avian-flu
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