Will a G4 swine flu virus cause the next pandemic?

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Chinese researchers warn of the emergence of a new strain of virus, G4, genetically descended from the H1N1 strain that caused a swine flu pandemic in 2009. These viruses are said to have "all the essential characteristics of a pandemic virus."

"Pigs will be the main intermediate hosts for the next generation of pandemic influenza viruses," said a team of researchers from Chinese universities and the China Center for Disease Control and Prevention. A new strain of swine flu has just been discovered, which appeared in China and is potentially dangerous: the G4 viruses.

According to a study published Monday in the American scientific journal Proceedings of the National Academy of Science, these viruses have "all the essential characteristics" capable of causing a future pandemic. They would also show "high adaptability to infect humans." An announcement to say the least worrying, while many countries still face the Covid-19 epidemic.

What is this new strain of virus?

Between 2011 and 2018, researchers analyzed 30,000 nasal swabs taken from pigs in slaughterhouses in 10 Chinese provinces and a veterinary hospital. This work isolated 179 swine flu viruses, most of which were G4 viruses, which became predominant in pigs in 2016.

The researchers then conducted several laboratory experiments, as well as tests on ferrets (generally used in flu research because their symptoms are comparable to those of humans: fever, cough, sneeze). Thus, they noticed the ability of G4 viruses to replicate in human cells, in other words, to cling to it and reproduce there quickly.

The genotype of G4 viruses is very similar to that of H1N1 influenza, a virus that combines swine, avian, and human sequences and killed 280,000 people worldwide in 2009.

How are they transmitted?

According to the researchers, this type of virus is transmitted by the epithelial cells of the human respiratory tract. Pre-existing population immunity against seasonal flu does not provide protection against G4, they insist.

10.4% of Chinese workers are already contaminated

"There is an urgent need to closely monitor human populations, especially workers in the pig industry," say the scientists. A serological testing campaign for virus-specific antibodies established that 10.4% of workers and people working with pigs had already been infected with these viruses. This percentage rises to 20.5% among young people between 18 and 35 years old. And 4.4% of the general population would also be contaminated

"Such infectivity greatly increases the virus's ability to adapt to humans and raises concerns about the possible generation of pandemic viruses."

Raise awareness of the dangers of zoonoses.

For the time being, viruses have passed well in humans, but to date, no cases of person-to-person transmission (person-to-person contamination) have been identified. However, researchers fear that when exposed to humans, viruses adapt and mutate. "Pandemics occur when influenza A viruses with a new HA surface antigen can spread from human to human," they recall.

Scientists do not say that a new pandemic is about to emerge along with that of Covid-19. However, they want health authorities to take the risk seriously and call for close monitoring of these new viruses. "There is an urgent need to control the predominant G4 EA H1N1 viruses in pigs and closely monitor human populations, especially workers in the pig industry," they conclude.

"This work is a healthy reminder that we are constantly threatened by the emergence of zoonotic pathogens and that farm animals, with which humans are more in contact than wildlife, may be major pandemic viruses," says James. Wood, head of the department of veterinary medicine at the University of Cambridge.

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