China study reveals swine flu virus may cause pandemic

Is humanity in new danger? Researchers have discovered a strain of swine flu virus in China with all the characteristics capable of causing a future pandemic, according to a study published Monday June 29 in the American scientific journal PNAS. The viruses are called G4 and are genetically descended from the H1N1 strain, which caused a pandemic in 2009: they “have all the essential traits showing high adaptability to infect humans”, write the authors, scientists from Chinese universities and the Center for Prevention and Control of Chinese Diseases.

The work presented is voluminous: from 2011 to 2018, 30,000 nasal swabs were taken from pigs in slaughterhouses in 10 Chinese provinces and in a veterinary hospital, making it possible to isolate 179 swine flu viruses. The majority were of the new variety, which has become dominant in pigs since 2016. The researchers then carried out various experiments in the laboratory and on ferrets, animals widely used in influenza research because their symptoms are comparable to those of humans: they have a fever, cough and sneeze.

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They observed that G4 viruses were more infectious, replicated in human cells and caused more severe symptoms in ferrets than other strains. In addition, according to in vitro tests, the immunity obtained after contact with human seasonal influenza viruses does not protect against G4.

Human-to-human transmission?

The other bad news is that workers and people working with pigs were relatively numerous to have been infected, 10.4%, according to blood tests which tested for the presence of antibodies to the virus. 4.4% of the general population also appeared to be infected. The virus has therefore already spread to humans, scientists say, but there is no evidence that it can be transmitted from human to human. Today is their fear. “Pandemics occur when influenza A viruses with a new HA surface antigen become capable of being transmitted from human to human,” the researchers conclude. The concern is that infections of humans with the G4 viruses do not lead to human adaptation and do not increase the risk of a human pandemic. “

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There is an urgent need, they say, to put in place surveillance of populations working in contact with pigs. “The work is a salutary reminder that we are constantly at risk of the emergence of zoonotic pathogens and that farm animals, with which humans are more in contact than with wild animals, are the source of important pandemic viruses Said James Wood, head of the department of veterinary medicine at the University of Cambridge. Asked about the virus, a spokesman for the Chinese Ministry of Foreign Affairs said during a regular press briefing on Tuesday, June 30, that China “will pay close attention to its development” and will take action. measures necessary to contain its spread.

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