Scientists have created a life-threatening virus that closely resembles the 1918 Spanish flu strain that killed an estimated 50m people in an experiment labelled as “crazy” by opponents.

US researchers said the experiments were crucial for understanding the public health risk posed by viruses currently circulating in wild birds, but critics condemned the studies as dangerous and called on funders to stop the work.

Scientists at the University of Wisconsin-Madison used a technique called reverse genetics to build the virus from fragments of wild bird flu strains. They then mutated the virus to make it airborne to spread more easily from one animal to another.

“The work they are doing is absolutely crazy. The whole thing is exceedingly dangerous,” said Lord May, the former president of the Royal Society and one time chief science adviser to the UK government. “Yes, there is a danger, but it’s not arising form the viruses out there in the animals, it’s arising from the labs of grossly ambitious people.”

Influenza viruses circulate freely in wild bird populations. Most remain in chickens, ducks and other birds, but occasionally strains mutate into a form that can infect humans. The H5N1 bird flu strain has killed at least 386 people since 2003, according to WHO figures. The Spanish 1918 flu is thought to have come from birds too.

Writing in the journal Cell Host and Microbe Yoshihiro Kawaoka describes how his team analysed various bird flu viruses and found genes from several strains that were very similar to those that made up the 1918 human flu virus. They combined the bird flu genes into a single new virus, making a new pathogen that was only about 3% different from the 1918 human virus.

The freshly made virus – the first of several the team created – was more harmful to mice and ferrets than normal bird flu viruses, but not as dangerous as the 1918 strain. It did not spread between ferrets and none of the animals died. But the scientists went on to mutate the virus, to see what changes could make it spread. Seven mutations later, they had a more dangerous version that spread easily from animal to animal in tiny water droplets, the same way flu spreads in humans.

Kawaoka, who led the research in a high-security lab at the University of Wisconsin-Madison, said the work highlighted how flu viruses found in wild bird populations had the potential to adapt to humans and cause a pandemic.

Follow-up experiments showed that the 2009 swine flu vaccine and the anti-viral drug tamiflu should be effective against the virus. “This is important information for those making decisions about surveillance and pandemic preparedness,” Kawaoka told the Guardian…. see more

source: Guardian UK