Indian Institute of Science study warns of rising human infection risk from evolving bird flu strain

Time of India

a day ago

Bengaluru: Three decades after the H5N1 influenza virus was first detected in birds, scientists say a particular branch of the virus is inching closer to becoming a serious human threat.
Researchers at the Indian Institute of Science (IISc) in the city have identified specific genetic mutations in the currently circulating 2.3.4.4b clade that may be increasing its potential to infect people.
"This clade has infected many mammalian species and is adapting to [non-human] mammals, which is a concern for human adaptation…It is panzootic, causing unprecedented mortality in birds and mammals, along with several sporadic human infections," said Kesavardhana Sannula, assistant professor in IISc's department of biochemistry, who led the study.
H5N1's surface proteins — type 5 haemagglutinin (H5) for cell entry and type 1 neuraminidase (N1) for viral spread — are key to its infectivity. When the virus jumps to a new host, mutations in its genome can help it survive, and sometimes thrive, in the new environment. The IISc team set out to examine whether the 2.3.4.4b clade was evolving proteins that could make the leap to humans easier — and which animal hosts might be accelerating that shift, IISc said Tuesday.
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Using computational tools, the team analysed nearly 43,000 protein sequences: 7,000 from birds, 820 from non-human mammals, and 35,000 from human influenza strains H1N1 and H3N2. They looked for amino acids under "selection pressure"— rapidly changing regions — and tracked how these mutations were distributed across the viral polymerase complex, nucleoproteins, and haemagglutinin.
The mutations were then sorted into two categories: adaptive (helping the virus infect humans) and barrier (hindering cross-species spread).
Their model also ranked potential animal hosts by the risk their adapted viruses could pose to humans. Fox-adapted strains, surprisingly, appeared more dangerous than cattle-adapted ones.
"This clade is acquiring the same key mutations that pandemic human influenza strains possess, which could be a growing risk," said Ranjana Nataraj, the study's first author. The findings, the researchers argue, make a strong case for proactive, targeted surveillance — especially in mammals that can act as "stepping-stone" hosts for the virus's adaptation to humans.
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