Immunologists today expressed concern about the "dangerous" work of scientists in China who created a hybrid bird flu virus that can spread in the air between guinea pigs, and now lives in a lab freezer.
The team from the Chinese Academy of Agricultural Sciences and Gansu Agricultural University wrote in the journal Science they had created a new virus by mixing genes from H5N1 "bird flu" and H1N1 "swine flu".
H5N1, transmitted to people by birds, is fatal in about 60 per cent of cases, but does not transmit between humans - a characteristic that has prevented a pandemic so far.
Since 2003, H5N1 has infected 628 people, killing 374, according to the World Health Organisation.
H1N1, which erupted in Mexico, is highly transmissible and infected a fifth of the world's population in a 2009-10 pandemic, but is about as lethal as ordinary flu.
The new mutant virus was easily transmitted between guinea pigs through respiratory droplets - which the Chinese team said proved the deadly H5N1 virus may need but a simple genetic mutation to "acquire mammalian transmissibility".
Flu hybrids can arise in nature when two virus strains infect the same cell and exchange genes in a process known as reassortment, but there is no evidence that H1N1 and H5N1 have done so yet.
But some observers fear that science is putting mankind at risk by preemptively creating such mutants.
"If there was ever an error (and) they got out or there was a leak... This could infect people and cause anywhere between 100,000 and 100 million deaths," virology professor Simon Wain-Hobson of France's Pasteur Institute told AFP.
There was, however, a view that the experiment was a valuable wakeup call, showing that the two viruses, both still infecting people around the world, can swap genes.
"I do believe such research is critical to our understanding of influenza. But such work, anywhere in the world, needs to be tightly regulated and conducted in the most secure facilities, which are registered and certified to a common international standard," Jeremy Farrar, director of the Oxford University Clinical Research Unit in Vietnam, was quoted as saying by Nature News.
