Bird flu — the next pandemic?

Since 2013, nearly 800 people have contracted avian influenza, mostly from poultry markets, but the infection has ended there as it is unable to spread from person to person.

Public health authorities are now concerned that the H7N9 strain of avian influenza is just a few genetic mutations away from being able to spread from human to human, which could lead to a pandemic. In order to be ready with a quick response to this potentially deadly scenario, an international team of scientists has been looking at the genetic mutations that could see ‘bird flu’ spread between humans.

Researchers headed by James Paulson of The Scripps Research Institute, in California, have been looking at the molecular structure of a particular protein found on the surface of the influenza virus, H7 hemagglutanin. This protein helps the flu virus latch onto host cells. Paulson’s team have focused their efforts on the gene that codes for the H7 hemagglutanin protein.

There are 16 different subtypes of hemagglutanin found in various influenza strains but thus far only three have been found in human flu strains — H1, H2 and H3. Avian influenza strain H7N9 specifically targets bird cells but a transition to human specificity is only a few genetic mutations away from causing a universal pandemic.

Molecular modelling was used to identify potential mutations that would make the leap from bird to human specificity, followed by experimental cell line testing. The mutant hemagglutanin proteins were then harvested to see how well they bound to human or bird receptors. It was found that triple-mutant H7 hemagglutanins had a preference for human trachea tissue.

While safety concerns prevented the researchers from introducing these triple-mutant H7 hemagglutanins into actual H7N9 viruses, the research team recommends authorities remain vigilant for such mutations in future bird flu outbreaks.

Research published earlier this year by the University of Hong Kong found that a single nucleotide, that was first identified in H9N2 strains in early 2000, is somehow involved in avian flu strains making the leap from birds to humans.

Published in PLOS Pathogens, this research was funded in part by National Institutes of Health Grants R56 AI11765 (to IAW), GM100058, GM103390 and U01-CA207824 (to RJW) and AI099274 and AI114730 (to JCP).

Image credit: ©stock.adobe.com/au/Dmytro Flisak