Scientists in China have discovered a new type of swine flu that is capable of triggering a pandemic, according to a study published Monday in the US scientific journal PNAS.
The name G4, it is genetically derived from the H1N1 strain that caused a pandemic in 2009.
It has "all important characteristics of being highly adapted to infecting humans," say the authors, researchers at Chinese universities and China's Center for Disease Control and Prevention.
From 2011 to 2018, researchers took 30,000 pigs from pigs in the slaughterhouses of 10 Chinese provinces and at a veterinary hospital to isolate 179 swine flu viruses.
The majority were of a new species that has been dominant among pigs since 2016.
The researchers then conducted various experiments, including ferrets, which are widely used in influenza studies because they experience similar symptoms as humans – mainly fever, coughing and sneezing.
G4 was observed to be highly contagious, replicating in human cells and causing more severe symptoms in ferrets than other viruses.
Tests also showed that any immunity humans get when exposed to seasonal flu does not provide protection against G4.
According to blood tests showing antibodies created by exposure to the virus, 10.4 percent of pig workers had already been infected.
The tests showed that as many as 4.4 percent of the population in general also appeared to have been exposed.
Therefore, the virus has already passed from animal to human, but there is no evidence that it can be transmitted from human to human – scientists' main concern.
"It is worrying that human infection with G4 virus will increase human adaptation and increase the risk of a human pandemic," the researchers wrote.
Asked about the virus on Tuesday, Chinese Foreign Ministry spokeswoman Zhao Lijian told a regular press release that China "has been closely monitoring developments" and will take all necessary measures to prevent proliferation and outbreaks.
The study authors asked for urgent measures to monitor people working with pigs.
"The work comes as a reminder that we are constantly risking new occurrences of zoonotic pathogens and that farmed animals, which humans have greater contact with than wildlife, can serve as the source of important pandemic virus," said James Wood, head of the Department of Veterinary Medicine at Cambridge University.
A zoonotic infection is caused by a pathogen that has jumped from a non-human animal to a human.