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Scientists unravel bird flu virus’ propensity to infect humans

TV Jayan New Delhi | Updated on July 23, 2021

Though unconnected, it came out a few days after the first suspected human death

While authorities are struggling to ascertain how the 11-year-old boy who died of bird flu in Gurugram contracted the infection, a team of Indian researchers – in a totally unconnected work – has shown that some strains of bird flu virus are close to acquiring the ability to infect higher order animals such as mammals.

The study, carried out by researchers led by Richa Sood of the National Institute of High Security Animal Diseases (NIHSAD) in Bhopal, a constituent laboratory of the Indian Council of Agricultural Research (ICAR), assumes significance because this is one of the first studies to report mammalian adaptation markers in H9N2 virus isolated from birds found around five wetlands in Maharashtra.

Exposure to humans

The study, which appeared in Infection, Genetics and Evolution, is important because it showed that H9N2 viruses have already acquired adaptation markers – which might facilitate human infection – in case of direct exposure to humans or by way of mixing genes with other influenza viruses (through what is called genomic reassortment) such as highly pathogenic avian influenza H5N1, and H7N9, among others.

For the study, the NIHSAD scientists collected over 850 excreta samples from 10 avian species from around five wetlands in the State – Uran, Nadhur Madhyameshwar, Navegaon, Jayakwadi and Ujani. The scientists found the presence of H9N2 virus in around 4 per cent samples they tested.

Spread of virus

As these wetlands fall in the route of a major migratory route – Central Asian Flyway – the scientists said they are worried the mutation can spread to other geographies.

“Although on preliminary level the influenza viruses are quite distinct in terms of their host specificity, but when avian influenza viruses continue to circulate in different avian hosts, they might acquire some mutations (changes in their RNA), which facilitate their spillover to humans,” said Sushant Bhat, a post-doctoral researcher working with Pirbright Institute in the UK, who contributed to the study.

“India had been very lucky in the sense that although (various bird flu viruses such as) H9N2, H5N1 and H5N8 have repeatedly been detected in poultry birds and there have been some isolated reports of human infection, no death had been reported until recently,” Bhat told BusinessLine.

About two years ago, a one-and-a-half-year-old boy from a Maharashtra village is said to have contracted H9N2 infection, which could be the first reported case of an avian flu virus jumping to humans in the country. This was discovered during a community survey by the National Institute of Virology, Pune.

According to Bhat, an influenza virus has eight segments in its genome. When two influenza viruses infect the same cell, different segments can mix and match and theoretically lead to the emergence of 256 different viruses, with each virus having a different set of eight segments.

“In the view of the high endemicity of H9N2 viruses and recurrent reassortment events with other circulating AIVs, these viruses do pose a potential public health risk,” said the scientists in their report.

Published on July 23, 2021

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