Scientists warning of rising threat from bird flu

Chinese scientists studying the evolution of H7N9 flu viruses have found that mutations of the virus pose increased threats to humans.

They spent four years doing their research, collecting more than 110,000 samples from poultry markets and slaughterhouses in over 20 provinces, Chen Hualan, director of the National Avian Influenza Reference Laboratory, told reporters.

They evaluated the evolution of H7N9 viruses isolated from avian species and found 23 different genotypes. Some of the viruses were not lethal in mice or ferrets, but, via replication in ferrets, mutated and became highly lethal. The viruses were easily spread among ferrets by breathing.

“Our study indicated that the new H7N9 mutations are lethal to chickens and pose an increased threat to humans, thus highlighting the need to control and eradicate H7N9 viruses to prevent a possible pandemic,” Chen said.

H7N9 was first reported in humans in China in March 2013 and is most likely to cause an epidemic in winter and spring.