Professor Chen and her colleagues deliberately mixed the H5N1 bird-flu virus, which is highly lethal but not easily transmitted between people, with a 2009 strain of H1N1 flu virus, which is very infectious to humans.
They warned there is a danger that the new viral strains created by mixing bird-flu virus with human influenza could escape from the laboratory to cause a global pandemic killing millions of people.
They claim they are doing this to help develop vaccines and such like.
Lord May of Oxford, a former government chief scientist and past president of the Royal Society, denounced the study published today in the journal Science as doing nothing to further the understanding and prevention of flu pandemics.
The study, which was carried out in a laboratory with the second highest security level to prevent accidental escape, resulted in 127 different viral hybrids between H5N1 and H1N1, five of which were able to pass by airborne transmission between laboratory guinea pigs.
“We don’t know the pathogenicity [lethality] in man and hopefully we will never know. But if the case fatality rate was between 0.1 and 20 per cent, and a pandemic affected 500 million people, you could estimate anything between 500,000 and 100 million deaths,” he said.