Researchers have found that the one of the five strains of the H7N9 was able to spread and infect 100% through the air. The researchers used ferrets because a flu virus that transmits well between humans will also transmit well between ferrets; but ferrets aren’t a perfect model because they don’t take into account any pre-existing immunity in the human population. To test the five strains of the H7N9 virus. Some ferrets were directly infected and others were placed in nearby cages to see if the ferrets got sick by breathing the same air. Although all five strains spread through the air, only one was successful to infect all the ferrets. The researchers stated that the H7N9 strain is highly contagious between ferrets.

As of right now, there are no reports that show any sustained human-to-human transmission of the virus. But Dr. Richard Webby, a bird flu expert at St. Jude Children’s Research Hospital in Memphis, Tenn., said that if the virus undergoes a few more genetic mutations it is likely to be able to gain the ability to spread between humans. There more chances the virus gets to infect people, the more likely it will undergo the mutations needed to make it contagious to humans.

The H7N9 virus emerged in February in China, and has infected 132 people with 43 fatalities. The virus is believed to transmit from birds, specifically chickens, to humans. It’s difficult to see which chickens are infected because the virus doesn’t cause any symptoms in the chickens. In order to reduce human infection and exposure, the infected birds have to be identified first. Dr. Webby said that the spread of the virus is not inevitable.

The good news is that the outbreak is lowering this summer and there have been no cases since the end of May.