WASHINGTON • Researchers in China have discovered a new type of swine flu that is capable of triggering a pandemic, according to a study published early this week in the US science journal PNAS.
Named G4, it is 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 Centre for Disease Control and Prevention.
From 2011 to 2018, researchers took 30,000 nasal swabs from pigs at slaughterhouses in 10 Chinese provinces and at 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 researchers then carried out 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 serious symptoms in ferrets than other viruses. Tests also showed that any immunity humans gain from exposure to seasonal flu does not provide protection from G4.
According to blood tests which showed up antibodies created by exposure to the virus, 10.4 per cent of swine workers had already been infected. The tests showed that up to 4.4 per cent of the general population appeared to also have been exposed.
The virus has therefore already passed from animals to humans but there is no evidence yet that it can be passed from human to human - the scientists' main worry.
"It is of concern that human infection of G4 virus will further human adaptation and increase the risk of a human pandemic," the researchers wrote.
A World Health Organisation (WHO) spokesman yesterday said the findings underscored the importance of influenza surveillance during the Covid-19 pandemic.
"It also highlights that we cannot let our guard down on influenza and need to be vigilant and continue surveillance even in the coronavirus pandemic," said WHO's Mr Christian Lindmeier.
The tests showed that up to 4.4 per cent of the general population appeared to also have been exposed. The virus has therefore already passed from animals to humans but there is no evidence yet that it can be passed from human to human - the scientists' main worry.
Chinese Foreign Ministry spokesman Zhao Lijian said China "has been paying close attention to its development" and will take all needed action to prevent its spread.