H7N9 close to being transmittable to humans

May 23, 2013, Toronto, ON – A new study shows that the H7N9 flu virus can pass between ferrets, even sometimes spreading by airborne transmission.

While the airborne spread wasn’t highly efficient, the work suggests this virus is more closely adapted to spread among mammals than other bird flu viruses.

The research was done by researchers in China, Hong Kong, the United States and Toronto and is published in the journal Science.

Malik Peiris, one of the authors, says that the research is part of the process of assessing the risk posed by the virus, which has infected about 130 people in China and Taiwan since late February.

The researchers also experimentally infected pigs; but though they got infected, they did not spread the virus to uninfected pigs.

Peiris says that means this virus probably did not kill the thousands of pigs found in a river near Shanghai around the time the H7N9 outbreak was first spotted.

“So I think what these data would suggest is that it is pretty unlikely that this virus came from pigs. And by implication the dead pigs in Shanghai were probably not related to this story,” says Peiris, who is the head of microbiology at the University of Hong Kong.

Ron Fouchier, a flu virologist at Erasmus Medical Centre in Rotterdam, the Netherlands, says the work shows this virus can do something other bird flu viruses haven’t been able to do.

Scientists would not expect to see avian flu viruses spread among ferrets by airborne transmission unless they are genetically modified to do so, says Fouchier, who was not involved in this study.

“Other avian viruses don’t do this without further adaptation,” Fouchier says.

“You do this with H5N1 with a virus that comes out of humans or poultry, it won’t transmit. And you do this with any other avian virus, it won’t transmit. But this one does.”

Both Fouchier and Peiris say the work suggests H7N9 needs to be considered as a serious risk.

To date there has been no sign of sustained human-to-human spread of the virus, but there have been a number of clusters of cases which suggest the possibility of limited person-to-person spread.