Scientists find swine flu strain with pandemic potential

Researchers in China have discovered a new type of swine flu that is capable of triggering a pandemic, according to a study published on Monday in the US science journal PNAS.

Named G4, genetically descended from the H1N1 strain that caused a pandemic in 2009.

It possesses "all the essential hallmarks of being highly adapted to infect humans," say the authors, scientists at Chinese universities, and China's Center for Disease Control and Prevention.

From 2011 to 2018, researchers took 30,000 nasal swabs from pigs in slaughterhouses in 10 Chinese provinces and a veterinary hospital, allowing them to isolate 179 swine flu viruses.

The majority were of a new kind, which has been dominant among pigs since 2016.

The scientists then carried out various experiments, including on ferrets, which are widely used in flu studies because they experience similar symptoms to humans - principally fever, coughing, and sneezing.

G4 was observed to be highly infectious, replicating in human cells, and causing more severe symptoms in ferrets than other viruses.

Tests also showed that any immunity humans gain from exposure to seasonal flu does not protect G4.

According to blood tests that showed up antibodies created by exposure to the virus, 10.4 percent of swine workers had already been infected.

The tests showed that as many as 4.4 % of the general population also appeared to have been exposed.

The virus has, therefore, already passed from animals to humans, but there is no evidence yet that it can be transferred from human to human - the scientists' main worry.

"It is of concern that human infection of G4 virus will further increase the risk of a human pandemic," the researchers wrote.

The authors called for urgent measures to monitor people working with pigs.