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May 5, 2009

Pandemics: more but less?

One of the advantages of having a fairly recent blog is that there is little readers to complain about the lack of update of the recent weeks.
That being said, this silence was not exactly planned, and I will try to post more often in the future.

The recent flu outbreak has captured the headlines, and I have wondering about the way scientific information is broadcast to the general population.
In particular, is it good practice to use, without further explanations, the notion of pandemic.

WHO scientists use technical terms, and rightly so, of course. It is easy to imagine the anger, were WHO (or any official organisation) to use ambiguous terms.

However, it must be noted that recent changes in our societies modified the implications of pandemics.
Up to a couple of decades ago, a pandemic really was bad news: you would need a large pool of infected individuals for the disease to spread globally, (in order to compensate for the limited exchanges between continents), and you would have to wait for a large number of casualties before a link could be made between these, (to compensate for the lack of efficient sequencing and monitoring resources).
In that sense, there was a strong correlation between what was identified as a pandemic (a disease outbreak spanning worldwide) and what corresponded to a very virulent infection.

The situation is quite different today. Population mobility implies a very rapid spread of any new disease (or strain thereof), as was observed in recent days. Similarly, a few serious cases are enough to draw very high attention and close monitoring of the outbreak.

A pandemic used to be identified a posteriori, and only in instances when the involved strain was virulent enough. In the general population pandemics of the past are, therefore, reminded by the thousands (or millions) of casualties they never failed to induce.
This is no longer the case, and an outbreak can reach level 5 (out of 6) in the WHO phases of pandemic alert before a thousand people are infected.

It would be very useful if media reports could explain that crucial change, so that we can prevent ourselves from excessive reactions.
In the current world, it is likely that we will regularly have outbreaks reaching high levels of alert, with only a fraction of them turning out to be as deadly as the ones we remember from the past.

This is the whole point of having an alert system, after all!