Daijiworld Media Network - New Delhi

New Delhi, Nov 29: New research from the Universities of Cambridge and Glasgow highlights a worrying trait of avian influenza (bird flu) viruses: unlike human flu viruses, they can replicate at temperatures higher than a typical fever, potentially increasing their danger to humans.

Human influenza viruses (Influenza A) are usually suppressed by fever. Even a 2°C rise in body temperature can turn a potentially lethal infection into a mild disease. However, the study shows that this natural defense is less effective against bird flu viruses, which tend to thrive in the lower respiratory tract of humans and in the guts of birds—natural hosts like ducks and seagulls—where temperatures can reach 40–42°C.

Key Findings:

• Avian flu viruses can withstand high temperatures that would normally inhibit human flu viruses.
• The PB1 gene, critical for viral genome replication, plays a major role in this temperature resilience. Viruses with avian-like PB1 genes remained active even under fever conditions.
• In laboratory models, mice exposed to elevated temperatures mimicking fever were protected from human-origin flu virus but not from avian-origin viruses, which caused severe illness.

Professor Sam Wilson of the Cambridge Institute said, “Understanding what makes bird flu viruses cause serious illness in humans is crucial for surveillance and pandemic preparedness, especially given the pandemic threat posed by H5N1 viruses.”

The study, published in Science, underscores the importance of monitoring bird flu viruses closely, as human infections, though rare, have historically shown high fatality rates, such as H5N1 infections with over 40% mortality.

In short, while fever is an effective defense against seasonal flu, it may not be enough to protect humans from avian influenza, making continued surveillance and preparedness critical.