While the latest official news from China says that the H7N9 bird flu outbreak is now under control, a new international study urges continued caution.
According to official Chinese figures, the virus has claimed 36 lives among 131 cases, mostly in people with exposure to poultry, and there have been no further human cases since May 8. There were some instances of multiple cases in families, suggesting the possibility of transmission between humans.
Published in the journal Science on May 23, a new paper emphasizes that the virus is “infectious and transmissible in mammals,” adding that human-to-human transmission may be possible “under appropriate conditions.”
“This is a more infectious virus—it has a higher intrinsic transmissibility [among mammals]—than most of the avian viruses we’ve seen in the past,: study co-author Dr. Richard Webby at St. Jude Children’s Research Hospital in Memphis told NPR.
“On a scale from 1 to 10—from an avian virus with no potential to infect humans to a fully human-adapted strain—we don’t know exactly where this H7N9 is,” Webby added. “But I think we can safely say from these data that it might be closer to 10 than the avian viruses we’ve seen infecting humans in the last decade.”
Using ferrets and pigs as mammalian models, the research shows that the virus spreads easily when ferrets are in close contact, namely by touching, coughing, and exchange of body fluids.
“This study was designed to give us clues about the transmission of H7N9 which has affected some humans in China,” explained study co-author David Kelvin at the University of Toronto in a press release. “The animals used in the study had very mild clinical symptoms as a result of their exposure to the virus and it was clear that very close contact was required for transmission. It also appears that this virus in its present form does not transmit very well through the air.”
Kelvin added that, although the research was conducted on animals, “health care workers are at risk for transmission as they are in close contact with the individuals.”
The researchers also noted that both the ferrets and pigs were shedding the virus before they showed clinical signs of infection, showing that the disease could spread even when animals appear to be healthy.
“There’s a bit of a worry in my mind that the urgency to do something about this will drop,” Dr. Webby told NPR.
“We really need to get on top of this virus and get it out of animal populations. Otherwise it’s just not going to go away.”