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A new virus capable of causing a pandemic has been discovered in pigs in China

It is a strain called G4 and descending from H1N1 which in 2009 had pandemic spread. It is believed that it has already passed to humans, but there is no evidence that it can be transmitted from man to man

AGI – Researchers have discovered a strain of the swine flu virus in China with all the characteristics capable of provoking a future pandemic. A study published in the American scientific journal Pnas reports this.

The viruses, called G4, are genetically descended from the H1N1 strain that caused a pandemic in 2009. “They have all the essential traits that show a high adaptability to infect humans,” write the authors, scientists from Chinese universities and Central China. for disease prevention and control.

The work presented is voluminous: from 2011 to 2018, 30 thousand nasal swabs were collected from pigs in slaughterhouses in 10 Chinese provinces and in a veterinary hospital, allowing to isolate 179 swine flu viruses. Most represented 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 flu research because their symptoms are comparable to human ones: fever, cough and sneezing. They observed that G4 viruses are more infectious, replicable in human cells and cause more severe symptoms in ferrets than other strains. Furthermore, according to in vitro tests, immunity obtained after contact with human seasonal flu viruses does not protect against G4.

The other bad news is that the percentage of workers and people infected because of contact with pigs was relatively high, 10.4%, according to blood tests that tested the presence of antibodies against the virus. At the general population level, the infection rate is 4.4%.

It is therefore believed that the virus has already passed to humans, scientists say, but there is no evidence that it can be transmitted from man to man. And that’s the main fear. “Pandemics break out when influenza A viruses with a new HA surface antigen become able to be transmitted from man to man,” the researchers conclude.

There is an urgent need, researchers write, to implement surveillance of people who work in contact with pigs. “At work there is a constant risk of the emergence of zoonotic pathogens. Farm animals, with which humans are more in contact than wild animals, are an important source of pandemic viruses,” said James Wood , head of the veterinary medicine department of the University of Cambridge.

When asked about the virus, a spokesman for the Chinese foreign ministry said during a daily press conference that China “pays close attention to its development” and that it will take the necessary measures to contain its spread.

The expert’s analysis

“The study represents a wake-up call, mainly because it is not the only pathogen with potentially pandemic characteristics, but we cannot make predictions.” Giovanni Maga, director of the Molecular Genetics Institute of the National Research Council (Cnr-Igm), told the AGI, commenting on the study published in the journal Proceeding of the National Academy of Sciences, in which experts from the University of Nottingham describe a new “pandemic potential” virus identified in a pig farm.

According to the statements of the British researchers, the virus, called G4, would have already made the leap inter species, but should not cause immediate concern although it should not be underestimated. “First of all, we must consider that the flu viruses, which are hundreds, find their main natural reservoir in migratory aquatic birds, but to pass to the human organism they need an incubator, or an intermediate species in which the genetic mixing takes place thanks to which the virus is able to transmit to humans, “explains Maga, adding that influenza pandemics in history, including that from H1N1 in 2009, have often been spread thanks to pigs, which in addition to the viruses of the species, have avian and human viruses .

“What happens is a remixing in the genes of pathogens, for which what are defined as reassorting are produced, that is, new viruses that can occasionally pass to humans. For this reason British researchers have asked themselves the problem of verifying whether in these years H1N1, which is now in circulation as a seasonal flu virus, had been scrambled.

The extended study on different farms has allowed to identify different viral strains that actually showed mixing of genes, including this G4 “, continues the director of the Institute of Molecular Genetics.” The strain is considered interesting for three reasons mainly: first of all, seen that the genetic characteristics of this virus could suggest that it could return to humans, the researchers conducted a serum prevalence study on breeders, in order to trace the presence of antibodies suitable to fight G4, and, according to the published results, the 10 percent of breeders had contracted the virus in the past, albeit without serious consequences, “says Maga.

“Secondly, by examining the existing literature, two studies were found according to which this virus had infected a child, who had recovered without consequences, and an adult man, whose symptoms instead led to death”, continues the researcher, specifying that these indications suggest the possibility that the virus is suitable for infecting the human organism, albeit with not serious consequences in almost all cases.

“The research team also used a culture to demonstrate that G4 has the ability to recognize receptors in the human body and to replicate within human cells. Using ferrets, it was possible to note that infected individuals could infect healthy ones. All this leads to the conclusion that the considered virus is actually able to transmit to the human organism “, the researcher continues, specifying that, although the pandemic potential is actually a concrete possibility, it does not necessarily result in an immediate danger, especially analyzing the documented cases.

“The literature indicates that some people have already been infected, but without serious consequences or particularly acute symptoms. The study, however, represents a wake-up call,” Maga continues, explaining that the presence of viruses in the animal world, and in particular among pigs, which can represent the main means of spreading new flu pandemics, it has led to a succession of five flu pandemics from the end of the 19th century to today.

“The last of 2009 had no particularly serious consequences, but it is absolutely unpredictable what could happen with the next”, concludes the expert.

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