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Newly identified swine flu could become a human pandemic
Researchers in China have identified an influenza virus called G4 that can infect both pigs and humans. While G4 is not yet able to spread from person to person, the scientists say that it has “all the essential hallmarks” of a future pandemic virus.
A newly discovered virus may have the potential to become a pandemic. Scientists have likened pigs to “mixing vessels” for generating pandemic influenza viruses because they host both mammalian and avian flu viruses.
When different strains of a virus occupy the same animal, they can swap genes to create new strains with the potential to infect new hosts.
Research led by Honglei Sun at China Agricultural University (CAU) in Beijing has identified such a strain in pigs that has already begun to infect humans.
Called G4, it incorporates genes from three distinct influenza strains:
a strain similar to viruses present in European and Asian birds
There is currently no evidence that G4 can pass from person to person. However, the presence of genes from the H1N1 pandemic strain suggests that it might develop this ability in the future.
Between 2011 and 2018, the research team analyzed about 30,000 nasal swabs taken from pigs at slaughterhouses in 10 Chinese provinces.
They also analyzed 1,000 swabs from pigs with respiratory symptoms that had received treatment at CAU’s veterinary teaching hospital.
The researchers identified a total of 179 swine influenza viruses, including G4, which began to predominate in the samples from 2016 onward. Describing their findings in the journal Proceedings of the National Academy of Sciences of the United States of America, the researchers say that G4 has “all the essential hallmarks of a candidate pandemic virus.”
They also detected antibodies to the virus in the blood of people who work at pig farms.
Out of 338 workers who underwent testing for G4, 35 (10.4%) received positive results. The infection rate was higher among younger workers aged 18–35, with nine out of 44 (20.5%) testing positive.
A household survey found antibodies to G4 in 4.4% of 230 people who underwent testing.
The scientists write that this level of infectivity “greatly enhances the opportunity for virus adaptation in humans and raises concerns for the possible generation of pandemic viruses.”