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Media reports are emerging of a new strain of flu which has the potential to become a pandemic.
It emerged recently in China and is carried by pigs, scientists say.
The BBC reports that, crucially, it can infect humans.
News of a potentially problematic flu strain is something the world does not want to contemplate as it struggles to deal with the Covid-19 coronavirus pandemic.
The BBC reports that researchers are worried the new virus could mutate so that it can spread easily between people.
They say it appears to be able to infect humans.
As with Covid-19, because it is new, people could have little or no immunity to the virus.
A swine flu outbreak in 2009 that began in Mexico was the last pandemic flu. It was less deadly than feared, largely because many older people had some immunity to it, probably because of its similarity to other flu viruses, the BBC reports.
The new flu strain, called G4 EA H1N1, is similar to 2009 swine flu. The scientists' research is in the journal Proceedings of the National Academy of Sciences.
Prof Kin-Chow Chang, who works at Nottingham University in the UK, told the BBC: "Right now we are distracted with coronavirus and rightly so. But we must not lose sight of potentially dangerous new viruses."
Professor Chang warned that although this virus was not an immediate problem, "we should not ignore it".
Professor James Wood from the University of Cambridge, told the BBC that the work "comes as a salutary reminder" that humans remain at risk of contracting new pathogens due to our reliance on farmed animals. we are constantly at risk of new emergence of pathogens, and that farmed animals.
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