Researchers Discover How Lethal Bird Flu Viruses Evolved And Started Harming Humans

Researchers of a new study found that the lethal H7N9 viruses evolved in a two step process from distinct H9N2 viruses, first affecting wild birds and then moving on to domestic birds and then humans.

Earlier this year, China reported H7N9 avian flu virus infections among humans for the first time. Scientists were left wondering how the bird virus evolved into a virus that proved to be harmful to humans as well. In a new study, researchers from Chinese Academy of Sciences found an answer to this dilemma.

They discovered that the deadly lethal H7N9 viruses evolved in a two step process from distinct H9N2 viruses. The virus first infected wild birds then moved on to domestic birds and finally through domestic birds started infecting humans too.

"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," said senior study author Taijiao Jiang of the Chinese Academy of Sciences.

The first H7N9 human infection was reported in March this year, followed by another 133 similar reports that resulted in approximately 44 deaths. The virus spread when people were exposed to infected poultry and contaminated environments rather than person-to-person contact. However, researchers have not ruled out the possibility of this virus evolving to such an extent that it can also be transmitted by person-to-person contact. Therefore, it is important to understand the evolutionary history of H7N9 so that appropriate strategies can be implemented to monitor and control any outbreaks.

For this, Jiang teamed up with Daxin Peng of Yangzhou University to analyze whole-genome sequences of avian flu viruses from humans, poultry and wild birds from China. They discovered that H7N9 viruses are genetically diverse, suggesting that complex genetic events were involved in their evolution.

They also found that H7N9 evolved by exchanging genetic materials with distinct viruses in a two-step process. The first step included mixing genetic material from H9N2 viruses and unspecified H7 and N9 viruses to create precursor H7N9 viruses. The next step involved the exchange of genetic material between the precursor H7N9 viruses and other H9N2 viruses to create new, genetically diverse H7N9 viruses.

"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 in a press statement.