The bird flu virus could be resistant to fever, one of the body’s main defense mechanisms. Cambridge researchers warn that avian strains continue to multiply even at high temperatures, raising the risk of a future pandemic threat.
One of the main mechanisms by which the body defends itself against infections is fever, which raises the internal temperature to make it difficult for viruses to replicate and cause severe forms of illness. But new research by the University of Cambridge in Great Britain suggests that this thermal defense mechanism does not work in the case of bird flu, writes the Daily Mail.
Common influenza viruses in humans usually remain in the upper respiratory tract, where the temperature is around 33 degrees Celsius. In the case of fever, it can reach up to almost 41 degrees Celsius, which slows down the infection and gives the immune system time to eliminate the virus.
Bird flu viruses, however, thrive in the lower respiratory tract and sometimes the gut of birds, where temperatures are between 40 and 42 degrees Celsius, levels generally higher than the human body can reach.
What scientists have discovered
To investigate how this influences the severity of an avian flu infection, scientists infected mice with a modified, lab-grown version of the PR8 flu virus – a strain considered safe for humans – that had the genetic section responsible for viral replication altered to resemble either human or avian flu viruses.
When the mice were kept at a temperature similar to that of a human fever, the results showed that the human flu-like version of the virus replicated with difficulty, while the bird flu-like version continued to multiply and caused severe illness.
The study needs to be confirmed by tests on other animals closer to humans, but the researchers caution that it suggests the fever may be ineffective against bird flu.
The scientists also added that the results could influence how bird flu is treated, indicating that it is not always beneficial to reduce the fever of a patient infected with bird flu.
The role of fever
Humans use fever as an infection-fighting mechanism because higher temperatures can denature essential proteins that the virus relies on to replicate. Thus, the multiplication of the virus is slowed down and the immune system gains time to attack and eliminate it.
Dr Sam Wilson, a molecular virologist at the University of Cambridge, who led the research, said: “Fortunately, humans don’t get infected with bird flu viruses very often, but we still see a few dozen human cases a year. Bird flu fatality rates in humans have historically been alarmingly high, as was the case with H5N1 infections, where mortality exceeded 40 percent.”
He added: “Understanding how avian influenza viruses cause serious illness in humans is critical to surveillance and pandemic preparedness. This is all the more important because of the pandemic threat posed by H5N1 avian viruses.”
The research comes after an American man in Washington state died after being infected with a strain of bird flu that had never been seen in humans before – only the second bird flu death ever recorded in the US. At the same time, the day before, the authorities in France warned that a bird flu pandemic could be more deadly than the Covid one.
How the study was conducted
In the new study published in the journal Science, researchers edited the virus’s PB1 genes, those genes that help the virus multiply.
These have been modified to match either those found in human influenza A viruses – the most common forms of influenza in humans – or those in the bird flu virus.
In the experiments, mice were infected with either the “human” version or the “bird” of the virus, and then they were kept either at room temperature or at a temperature that mimicked human fever.
Mice do not normally develop a fever in response to infection, but the researchers were able to mimic the fever by raising the ambient temperature to the level of a human fever, which also raised the rodent’s body temperature.
result
The results showed that rodents infected with the human flu-like version of the virus did not develop severe forms of the disease when exposed to 41C.
In contrast, rodents infected with the avian flu-like version developed severe disease even at this temperature.
Dr Matt Turnbull, a virologist at the University of Glasgow and first author of the study, said: “Monitoring bird flu strains is essential to help us prepare for possible outbreaks. Testing viruses with the potential to transmit to humans to assess how resistant they might be to the flu can help us identify more virulent strains.”
Experts warn that bird flu infections are more common in the autumn months as migratory birds – which can carry the virus – change their routes, spreading the virus to new areas.
There are still fears that the virus could mutate so that it can be transmitted between people, which could trigger a new outbreak similar to the Covid pandemic.
