Virological Risk Assessment of Pandemic Potential - EFSA Call for proposalsArchived

ECDC comment

​The European Food Standard Agency has recently published a call for proposals for a methodological framework for potentially pandemic influenza strains. Details of the call are available at the EFSA website. Proposals, which have to meet the usual EU/EFSA requirements (including needing to come from at least three countries) have to be received by September 29th 2011.

The European Food Standard Agency has recently published a call for proposals for a methodological framework for potentially pandemic influenza strains. Proposals, which have to meet the usual EU/EFSA requirements (including needing to come from at least three countries) have to be received by September 29th 2011.

ECDC Comment: (15th July 2011)The term risk assessment has more than one meaning. When applied to animal influenza and virological risk assessment for human health it most usually means the likelihood of an animal influenza viruses or recombinants becoming a human pandemic influenza virus, i.e. a risk assessment of their pandemic potential and this is what is meant in the EFSA call for proposals. Most animal influenza viruses do not have such potential. The virological risk assessment talks about a situation when a set of viruses emerges that has that potential, and it is realised  the viruses are able to infect humans, cause some disease and transmit efficiently from person to person. In addition a significant proportion of the population has to lack immunity to the virus.  That is what happened with A(H1N1)2009 viruses, but as yet has not happened for A(H5N1)viruses. The latter viruses only occasionally infect humans and their transmission from one human to another is even rarer. What has made A(H5N1) viruses of such interest to public health officials is their unusually high pathogenicity in the few humans infected and their unusual persistence in domestic birds while still developing genetically.(1)   Once the pandemic potential of an influenza virus is realised, as happened in Mexico for A(H1N1)2009 swine origin viruses a different type of risk assessment takes over, describing the features of human infection and disease and dictating the specific countermeasures to be used.

There is no agreed format for influenza virological risk assessment and no simple tests for pandemic potential. Rather there are a series of biological characteristics which hint at the risk. These include human cell and tissue tropism for example using glycan arrays (5-7), genetic structure (is the virus close in coding and structure to viruses that already transmit between humans and  transmissibility between animals accepted to be good models for human infection (such as ferrets).

The reason for wanting to undertake virological risk assessment is not just academic, though it will be valuable to understand what leads to particular animal viruses emerging as pandemic viruses. Rather it is to select which are the animal viruses that represent the greatest danger, those that have the highest pandemic potential. Diagnostics can be developed and made ready and those viruses can be added to candidate vaccine libraries of high growth assortments. The early stages of vaccine development can be undertaken and early trials undertaken. This would mean that for future pandemics it might be possible to have vaccines available before rather than after initial waves. Though it would not necessarily make decisions on whether and how to deploy them any easier.