Nasal swabs from more than 30.000 Chinese pigs over 7 years found an increase in the avian flu virus that replaced genes from several strains.
What we just don't need now is a new pandemic when we are already experiencing another. The discovery that Chinese pigs are increasingly infected with a strain of swine flu that has the potential to affect humans seriously worries infectious disease researchers around the world.
And it is yet another serious danger announced: the conditions of intensive breeding of Chinese pigs (and the planet in general) are there for all to see. Futuroprossimo.it also dealt with it some time ago.
Water on the fire
Robert Webster, a medical researcher, says that it is, for now, pure hypotheses. The fact that this variant of influence will easily pass on to and between humans is not an absolute certainty. “We just don't know that a pandemic will happen until it happens,” says Webster. It doesn't sound reassuring.
A combination of different viruses
When multiple strains of flu viruses infect the same pig, they can easily swap genes, a process known as 'reassortment'.
The new study, published today in the Proceedings of the National Academy of Sciences, focuses on a flu virus called G4. The virus is a unique blend of three lineages: the first is similar to strains found in European and Asian birds. The second is the H1N1 strain that caused the 2009 pandemic. The last is a North American H1N1 that has genes from avian, human and swine flu viruses.
The G4 variant is of particular concern because its core is an avian flu virus (to which humans have no immunity) with fragments of mammalian strains mixed in.
“From the data presented, it appears that this is a swine flu virus that is about to emerge in humans", he claims Edward Holmes, an evolutionary biologist at the University of Sydney who studies pathogens. "Clearly this situation needs to be monitored very carefully."
G4, as we discovered the swine flu variant that can trigger a new pandemic
As part of a project to identify potential pandemic influenza strains, a team led by Liu Jinhua of China Agricultural University (CAU) analyzed about 30.000 nasal swabs from pigs in slaughterhouses in 10 Chinese provinces and another 1000 swabs from pigs with respiratory symptoms observed at their school's veterinary teaching hospital.
The swabs, collected between 2011 and 2018, produced 179 swine flu viruses, most of which were G4 or one of the other five G strains of Eurasian avian ancestry. "The G4 virus has shown a sharp increase since 2016 and is the predominant circulating genotype in pigs detected in at least 10 provinces," they write.
Sun Honglei, the paper's first author, says the inclusion of G4 genes from the 1 H1N2009 pandemic "could promote virus adaptation" leading to human-to-human transmission. Therefore, "there is a need to strengthen surveillance" of Chinese pigs for influenza viruses, says Sun.
Because G4 is a real danger
Influenza viruses often jump from pigs to humans, but most are not passed on to humans. Two cases of G4 infections in humans have been documented and both were dead end infections that did not spread to other people.
"The likelihood of this particular variant causing a pandemic is low," he says Martha Nelson, an evolutionary biologist at the National Institutes of Health's Fogarty International Center who studies swine flu viruses and their spread in humans.
Nelson notes that no one knew about the H1N1 pandemic, passed from pigs to people, until the first human cases surfaced in 2009. “The flu may surprise us,” says Nelson. "And there is a risk that in times of Covid-19 we overlook threats of this type".
The new study offers only a small picture of the swine flu strains in China. A nation that has over 500 million pigs.
The "good" news is that the sample of research done does not show a very accurate snapshot. The bad thing is that we do not know if beyond G4 even worse preparations are made, 3 absolutely further sampling in Chinese pigs is needed.
"We need to be vigilant about other infectious disease threats even while COVID is happening because viruses don't care if we're already experiencing another pandemic," says Nelson.