The Influenza epidemic of 1918 created havoc amongst the population of the entire world. Designated the Spanish flu it killed an estimated 50 million people. It then went extinct.
But now, scientists at the University of Wisconsin-Madison created the virus anew from fragments of other existing wild bird flu strains. They then mutated the virus to make it airborne to spread more easily from one animal to another.
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 Influenza A(H5N1) has killed at least 386 people since 2003, according to WHO figures. The Spanish 1918 flu is thought to have come from birds too.
 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 potent version that spread easily from animal to animal in tiny water droplets - the same way Influenza spreads in humans.
The work is the latest in a series of controversial studies that have split the scientific community. In an article, one scientist argued that experiments like this could unleash a catastrophic pandemic if a virus escaped or was intentionally released from a high-security laboratory.
But, of course, Kawaoka defended the work, saying that critics failed to appreciate the impact of his and others' work on dangerous viruses. "There were discussions on the usefulness of stockpiling H5N1 [bird flu] vaccines until our H5N1 papers were published. Similarly, this paper strongly supports stockpiling anti-influenza drugs. If this is not a 'lifesaving benefit', what is?" he said.
 Watanabe et al: Circulating Avian Influenza Viruses Closely Related to the 1918 Virus Have Pandemic Potential in Cell Host and Microbe - 2014
 Lipsitch, Galvani: Ethical Alternatives to Experiments with Novel Potential Pandemic Pathogens in PLoS One - 2014