Airborne H7N9

Chinese scientists confirm that the avian flu virus subtype can spread through the air between ferrets.

Kate Yandell
Jul 19, 2013

WIKIMEDIA, GUY HAIMOVITCHThe H7N9 flu virus can spread between ferrets via respiratory droplets, according to a study published in Science yesterday (July 18). The news strengthens concerns that the virus could spread between humans.

The H7N9 bird flu has killed 43 people and infected 133 since February, according to the World Health Organization. The bulk of the cases were reported in April, and no new cases have been reported since May.

The researchers tested three human strains of the virus, as well as one strain isolated from a chicken and one from a pigeon. They tested the viruses’ transmissibility between pairs of ferrets because the small mammals are considered a close proxy for humans.

The inoculated ferrets were placed in nearby cages and divided by nets from the non-inoculated ferrets. None of the three ferrets exposed to chicken H7N9 contracted the virus. Of the three ferrets exposed to the pigeon H7N9, one contracted it. Two of the strains of human H7N9 infected one ferret each. But the third strain of human H7N9, isolated from a patient in the Anhui province of China, infected all three of the ferrets exposed to inoculated animals. When the scientists repeated the experiment with the Anhui virus, they got the same results.

Scientific American pointed out that the new study contradicts experiments published in Nature earlier this month (July 10) indicating that the Anhui strain of H7N9 did not readily spread between ferrets without close physical contact.

Regardless, the researchers say that keeping more people from being infected is paramount, as every time the virus is allowed to replicate in a human, it has an opportunity to mutate so that it becomes more transmissible. “Our findings indicate nothing to reduce the concern that these viruses can transmit between humans,” the researchers wrote.