Researchers chart evolution of deadly H7N9 bird flu

Chinese researchers determined that new H7N9 avian flu viruses evolved from distinct H9N2 viruses as part of a two-step process, according to a study published on Thursday in Cell Host & Microbe.

Researchers from the Chinese Academy of Sciences and Yangzhou University analyzed whole-genome sequences of avian flu viruses from human, poultry and wild birds from China. They found that H7N9 viruses are genetically diverse, which suggested that complex genetic events resulted in their evolution.

The authors said that understanding the evolutionary history of the viruses could help in the development of appropriate strategies for monitoring and controlling outbreaks.

"A deep understanding of how the novel H7N9 viruses were generated is of critical importance for formulating proper measures for surveillance and control of these viruses and other potential emerging influenza viruses," Taijiao Jiang, the senior author of the study, said.

The researchers found that the new H7N9 viruses resulted from a two-step process involving the exchange of genetic material between different viruses. The first step occurred when genetic material from H9N2 viruses and unspecified H7 and N9 viruses mixed to create precursor H7N9 viruses in wild birds. The second step involved the exchange of genetic material between the precursor H7N9 viruses and other H9N2 viruses to create new and genetically diverse H7N9 viruses in domestic birds in eastern China early last year.

"Our work not only re-enforces the important role of wild birds in the emergence of novel influenza viruses but also highlights the necessity of integrating data from infections in humans, poultry and wild birds for effective influenza surveillance," Jiang said.

Since it was detected in March, H7N9 viruses led to more than 130 human infections and at least 44 deaths.