Explained: What is G4 flu virus with ‘pandemic potential’ found by Chinese researchers?

Scientists report that the new strain (G4) has descended from the H1N1 strain that was responsible for the 2009 swine flu pandemic.

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The scientists identified the virus through surveillance of influenza viruses in pigs that they carried out from 2011 to 2018 in ten provinces of China. (File/AP Photo)

In a new research, scientists from China – which has the largest population of pigs in the world – have identified a “recently emerged” strain of influenza virus that is infecting Chinese pigs and that has the potential of triggering a pandemic. Named G4, the swine flu strain has genes similar to those in the virus that caused the 2009 flu pandemic.

The study was published Monday in the US science journal Proceedings of the National Academy of Sciences (PANS).

The scientists identified the virus through surveillance of influenza viruses in pigs that they carried out from 2011 to 2018 in ten provinces of China.

During this time, more than 29,000 nasal swabs were collected from slaughtered pigs and over 1,000 swabs or lung tissues were collected from farmed pigs that had signs of respiratory disease.

Out of these samples, the researchers isolated 179 swine flu viruses, the majority of which belonged to the newly identified G4 strain.

They also found that the G4 strain has the capability of binding to human-type receptors (like, the SARS-CoV-2 virus binds to ACE2 receptors in humans), was able to copy itself in human airway epithelial cells, and it showed effective infectivity and aerosol transmission in ferrets.

But why study pigs?

The scientists report that the new strain (G4) has descended from the H1N1 strain that was responsible for the 2009 flu pandemic. “Pigs are intermediate hosts for the generation of pandemic influenza virus. Thus, systematic surveillance of influenza viruses in pigs is a key measure for pre-warning the emergence of the next pandemic influenza,” states the study. It cannot be said if this new strain, if transmitted from pigs to humans, can transmit from one human to another.

The scientists suggest that controlling the prevailing G4 Eurasian-Avian like (EA) H1N1 viruses in pigs and closely monitoring human populations, especially workers in the swine industry, should be “urgently implemented”.

The 2009 swine flu pandemic

The WHO declared the outbreak of type A H1N1 influenza virus a pandemic in 2009 when there were around 30,000 cases globally. The US Centers for Disease Control and Prevention (CDC) defines swine flu as, “a respiratory disease of pigs caused by type A influenza viruses that regularly cause outbreaks of influenza in pigs. Influenza viruses that commonly circulate in swine are called “swine influenza viruses” or “swine flu viruses”. Like human influenza viruses, there are different sub-types and strains of swine influenza viruses”.