What’s G4 virus?

What is the G4 virus? Why does it have “pandemic potential” as some scientists say?

Simply put, it’s a new strain of the influenza or flu virus, it’s carried by pigs and can infect humans—much like its predecessor that caused the swine flu outbreak of 2009.

Researchers call the virus G4 EA H1N1. It is descended from the H1N1 strain and can grow and multiply in the cells that line the human airways—much like the current novel coronavirus that has brought the world to its knees.

The US Centers for Disease Control and Prevention defines swine flu as “a respiratory disease of pigs caused by type A influenza viruses that regularly cause outbreaks of influenza in pigs.

Like human influenza viruses, there are different sub-types and strains of swine influenza viruses, the CDC noted.

Chinese scientists found evidence of recent infection in people who worked in abattoirs and the swine industry in China when they looked at data from 2011 to 2018, the British Broadcasting Corp. (BBC) reported on its website.

Current flu vaccines do not appear to protect against it, although they could be adapted to do so if needed. However, researchers are concerned it could mutate further so that it can spread easily from person to person -- and trigger another global outbreak.

While it is not an immediate problem, they say, it has “all the hallmarks” of being highly adapted to infect humans and needs close monitoring. As it’s new, people could have little or no immunity to the virus, the BBC reported.

Scientists wrote in the journal Proceedings of the National Academy of Sciences that measures to control the virus in pigs, and the close monitoring of swine industry workers, should be swiftly implemented.

“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,” the study states.

The 2009 swine flu outbreak was the last pandemic flu the world encountered. It was less deadly than initially feared, largely because many older people had some immunity to it – probably because of its similarity to other flu viruses that had circulated years before, scientists said.

So far, the G4 strain hasn’t posed a big threat, but Prof. Kin-Chow Chang and colleagues who have been studying it told BBC health editor Michelle Roberts it is one to keep an eye on.

Chang, who works at Nottingham University in the UK, said: “Right now we are distracted with coronavirus and rightly so. But we must not lose sight of potentially dangerous new viruses.”

While this new virus is not an immediate problem, he said: “We should not ignore it.”

Scientists collected more than 29,000 nasal swabs from slaughtered pigs and over 1,000 swabs or lung tissues 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 that causes COVID-19 binds to ACE2 receptors in humans).

It was able to copy itself in human airway epithelial cells, and it showed effective infectivity and aerosol transmission in ferrets, the scientists said.

In theory, a flu pandemic could occur at any time, but they are still rare events, Roberts noted for BBC. Pandemics happen if a new strain emerges that can easily spread from person to person.

Although flu viruses are constantly changing - which is why the flu vaccine also needs to change regularly to keep up - they do not usually go pandemic.

The World Health Organization declared the outbreak of type A H1N1 influenza virus a pandemic in 2009 when there were around 30,000 cases globally.

A WHO statement said: “Eurasian avian-like swine influenza virus are known to be circulating in the swine population in Asia and to be able to infect humans sporadically.”

Prof James Wood, head of the Department of Veterinary Medicine at the University of Cambridge, said the Chinese scientists’ work “comes as a salutary reminder” that people are “constantly at risk of new emergence of pathogens.”

Wood also noted that farmed animals – with which humans have greater contact than with wildlife -- “may act as the source for important pandemic viruses.”

“It also highlights that we cannot let down our guard on influenza; we need to be vigilant and continue surveillance even during the COVID-19 pandemic.”

Topics: flu virus , G4 virus , US Centers for Disease Control and Prevention , swine flu
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