Wednesday, April 3, 2013

H7N9 - Betting its not a pandemic in the making.

So the world is watching the emergence of H7N9 avian influenza - the H7 strain not usually infecting humans - causing severe illness and death in China. But I think it is this paper: Using Routine Surveillance Data to Estimate the Epidemic Potential of Emerging Zoonoses: Application to the Emergence of US Swine Origin Influenza A H3N2v Virus,  and reflecting on the emergence of the 2009 pandemic that causes me to doubt the pandemic potential of an influenza virus that, when we first hear about it, is apparently directly associated with zoonotic spill over - not in all cases but in significant numbers of cases. 

I think the chance of us “being there” in the early days or weeks of the next pandemic and actually seeing it spill from animals to humans is extremely remote and so when we see significant numbers of cases associated with chicken or pig exposure, as in the current H7N9 issue and the recent pig associated H3N2 clusters in the USA,  then I suspect it will more often then not stay that way.    I suspect most of the initial spill overs will escape our surveillance and arise in humans without any immediately recognised links to animals – as did the 2009 H1N1 pandemic.  But this is just a probabilistic argument which will fail sometimes - hence the need to remain watchful.

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