Thursday 10 October 2013

Low transmission potential for H7N9 that was....remains to be seen what will be

Chowell and colleagues mathematically model influenza A(H7N9) virus transmission in a new article in BMC Medicine.

They conclude that the basic reproduction number (R; the average number of new cases arising from each exiting case) remained much less than 1 (0.1) for H7N9 infections, indicating the virus from earlier this year did not have pandemic potential. I guess we also know that now because we're not the midst of a pandemic. Good test of the model I guess.

The authors note that their...

..very generic model only requires information on the date of symptoms onset and could be applicable to a variety of emerging infections that include spillovers from a putative reservoir and human-to-human transmission.

Unfortunately, one need only look at the MERS-CoV data to see that those dates can be as rare as hen's teeth (pardon the avian pun) in some instances. Models are wholly reliant on good data.

The authors link the decline in the H7N9 outbreak principally to live bird market closures; but if those controls are relaxed (as they have been, I believe)....we hold our breath to see what re-emerges as the weather turns colder, birds intermingle and humidity changes. If indeed any of those things are what might lure out a new round of animal-to-human infections.

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