March 11, 2015

expert reaction to new paper studying pandemic potential of second wave of H7N9 influenza in China

A paper published in the journal Nature has reported the spread of the H7N9 strain of avian influenza from eastern to southern China, and the establishment of distinct variations in different regions. The authors suggest that these findings have relevance for wider disease monitoring and control.

Prof. Wendy Barclay, Chair in Influenza Virology, Imperial College London, said:

“The work from Yi Guan and his team shows that H7N9 avian influenza virus is widespread in birds across the whole of China. By collecting and sequencing the huge amount of samples documented, they can say this virus is changing in the very same ways we know that all other influenza viruses do change; by accumulating mutations and switching gene segments with other viruses – in this case mainly from the H9N2 avian viruses that are also prevalent in the live poultry markets that have been surveyed. Because the H7N9 virus doesn’t kill the chickens the chances of reassortment are even higher than for other more pathogenic viruses.

“What we don’t know from this paper is the significance of all these mutations that are accumulating as the virus persists and spreads. This is especially relevant for human health – does any of this change the pandemic potential of the virus? There is no biological characterization here, just a description of the state of play. Without experiments to link the sequence changes to virus characteristics (like altered receptor binding, increased replication in human cells at cool temperatures, or increased environmental stability), how will we know if clade 1, 2, or 3 pose the biggest threat? Some of the second wave viruses are recorded as having some mutations in regions associated with antigenicity – does this affect the efficacy of any vaccine seeds that have been generated so far?

“This work sets the scene, lays out the available information today and implies that tomorrow it might all be different. But without the accompanying virological experiments, we are simply watching a car crash in slow motion.”

‘Dissemination, divergence and establishment of H7N9 influenza viruses in China’ by Tommy Tsan-Yuk Lam et al. published in Nature on Wednesday 11 March 2015. 

Declared interests

None declared