One strain of the H7N9 bird flu virus appears to spread easily through the air between ferrets, which are a good model for how the virus may spread in humans, a new study from China says.
Researchers tested transmission of five strains of H7N9, all taken from people who got sick with the virus.
Some ferrets were directly infected with the virus, and others were placed in cages nearby to see if they got sick simply by breathing the same air. All five strains of H7N9 were able to spread through the air between ferrets, but four of the strains did not transmit very well. However, one strain was able to spread very well — it infected 100 percent of the ferrets who were exposed to it through the air.
So far, there have been no reports of sustained human-to-human transmission with H7N9 bird flu. But the new findings add to growing evidence that the virus likely needs to undergo just a few genetic mutations to gain the ability to spread between people, said Dr. Richard Webby, a bird flu expert at St. Jude Children’s Research Hospital in Memphis, Tenn., who was not involved in the new study. Webby acknowledged that this is still his “best guess.”
H7N9 emerged in China in February, and so far has infected 132 people, including 43 who have died.
Researchers know that a flu virus that transmits well between humans will transmit well between ferrets, Webby said. But ferrets aren’t a perfect model. For example, they don’t take into account pre-existing immunity in the human population, Webby said.
