How lethal bird flu viruses evolved

September 19, 2013

Deadly H7N9 avian flu viruses infected people for the first time earlier this year in China, but little is known about how they evolved to become harmful to humans. In a study published by Cell Press on September 19 in Cell Host & Microbe, an in-depth evolutionary analysis of whole-genome sequences of different types of avian flu viruses has revealed that new H7N9 viruses emerged from distinct H9N2 viruses in a two-step process, first occurring in wild birds and then continuing in domestic birds.

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

First detected in people in late March, H7N9 viruses have resulted in more than 130 human infections and at least 44 deaths. Most of these infections occurred after exposure to infected poultry or contaminated environments rather than person-to-person contact, but these viruses could evolve to become more readily transmissible among humans. This possible threat highlights the importance of understanding the evolutionary history of H7N9 viruses for developing appropriate strategies to monitor and control outbreaks.

To address this problem, Jiang teamed up with Daxin Peng of Yangzhou University and their collaborators 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.

Their analysis revealed that the new H7N9 viruses emerged through a two-step process involving the exchange of genetic material between distinct viruses. In the first step, which took place in wild birds, genetic material from H9N2 viruses and unspecified H7 and N9 viruses was mixed to create precursor H7N9 viruses. The second step, which occurred in domestic birds in eastern China early last year, 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 says.
-end-
Wu et al.: "Sequential Reassortments Underlie Diverse Influenza H7N9 Genotypes in China"

Cell Press

Related Viruses Articles from Brightsurf:

Sorting out viruses with machine learning
Researchers at Osaka University created a machine-learning system to identify single viral particles that cause respiratory diseases, including coronavirus, using silicon nanopores.

The rafts used by viruses
The study may suggest new strategies to limit virus attacks and prevent or combat diseases like Sars and Covid-19 based on biomedical and engineering principles.

Animals keep viruses in the sea in balance
A variety of sea animals can take up virus particles while filtering seawater for oxygen and food.

Hundreds of novel viruses discovered in insects
New viruses which cause diseases often come from animals. Well-known examples of this are the Zika virus transmitted by mosquitoes, bird flu viruses, as well as the MERS virus which is associated with camels.

First video of viruses assembling
For the first time, researchers have captured images of the formation of individual viruses, offering a real-time view into the kinetics of viral assembly.

Plant viruses may be reshaping our world
A new review article appearing in the journal Nature Reviews Microbiology highlights the evolution and ecology of plant viruses.

Checkmate for hepatitis B viruses in the liver
Researchers at Helmholtz Zentrum M√ľnchen and the Technical University of Munich, working in collaboration with researchers at the University Medical Center Hamburg-Eppendorf and the University Hospital Heidelberg, have for the first time succeeded in conquering a chronic infection with the hepatitis B virus in a mouse model.

How viruses outsmart their host cells
Viruses depend on host cells for replication, but how does a virus induce its host to transcribe its own genetic information alongside that of the virus, thus producing daughter viruses?

Mobile, instant diagnosis of viruses
In a first for plant virology, a team from CIRAD recently used nanopore technology to sequence the entire genomes of two yam RNA viruses.

How ancient viruses got cannabis high
THC and CBD, bioactive substances produced by cannabis and sought by medical patients and recreational users, sprung to life thanks to ancient colonization of the plant's genome by viruses, U of T researchers have found.

Read More: Viruses News and Viruses Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.