Scientists 'must not become complacent' when assessing pandemic threat from flu viruses

Steven Riley from Imperial College London, an author of the study, says: "There are too many strains of influenza viruses out there in non-human hosts to make it feasible to make preparations against each one. Instead, we need to get better at assessing the pandemic risks so that we know where best to focus our efforts. At the moment, this assessment is largely driven by a simple idea: animal viruses that cause sporadic human infections pose a greater risk than viruses that have not been documented to infect humans. But in fact, none of the viruses that caused the major pandemics of the last century were detected in humans before they emerged in their pandemic form."

Writing in the journal eLife, the scientists set out the steps that they consider necessary to increase our ability to assess pandemic risk. As influenza virus genome sequencing becomes cheaper, faster and more readily available, the data it generates has the potential to transform the research community's ability to predict the pandemic risk. However, it remains extremely difficult to predict just from a virus's genome what symptoms it will elicit in its host -- and hence how deadly the virus is. The researchers call for better integration of experimental data, computational methods and mathematical models, in conjunction with refinements to surveillance methodology.

However, they say that scientific insights into non‐human influenza viruses must not give way to complacency that the most substantial threats have been identified and characterized. They point out that several recent strains including the 2009 H1N1 "swine flu" pandemic virus and the recently emerged H7N9 viruses in China highlight the importance of remaining vigilant against as-yet unrecognized high risk viruses and the value of surveillance for influenza viruses in humans.

"No one can say with anything close to a hundred percent certainty when or where the next pandemic will start or which virus will cause it," says Dr Colin Russell from the Department of Veterinary Medicine at the University of Cambridge. "We are getting much better at identifying and assessing potential threats, but we must be vigilant about surprises lurking around the corner.

"We need to be prepared for a swift response, with coordinated action, to help mitigate the spread of the next pandemic virus. Without developing this ability to respond, we will have spent billions building systems just for watching the next pandemic unfold."