Nasal swabs from more than 30.000 Chinese pigs over 7 years found an increase in avian influenza virus that replaced the genes of several strains.
What we really don't need now is a new pandemic when we are already experiencing another one. The discovery that Chinese pigs are increasingly infected with a strain of swine flu that has the potential to affect humans seriously concerns infectious disease researchers around the world.
And it is yet another serious danger announced: the conditions of intensive breeding of Chinese pigs (and of 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, medical researcher, states that these are, for now, pure hypotheses. The fact that this variant of influenza will spread easily to and between humans is not an absolute certainty. “We just don't know a pandemic is going to happen until it happens,” Webster says. That doesn't sound reassuring.
A combination of different viruses
When multiple strains of influenza 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 mixture 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 influenza viruses.
The G4 variant is particularly concerning because its core is an avian influenza 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, how 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, yielded 179 swine flu viruses, most of which were G4 or one of five other G strains of Eurasian avian lineage. “The G4 virus has shown a strong 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, “it is necessary to strengthen surveillance” of Chinese pigs for influenza viruses, Sun says.
Because G4 is a real danger
Influenza viruses often jump from pigs to humans, but most do not then transmit between humans. Two cases of G4 infections have been documented in humans, 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, which jumped from pigs to people, until the first human cases emerged in 2009. “The flu can surprise us,” Nelson says. “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 precise snapshot. The bad news is that we don't know if things are getting worse after G4, 3 we absolutely need further sampling in Chinese pigs.
“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,” Nelson says.
