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Caution should be applied to predictions as well as to risks

Tim Black has an excellent article in Spiked about the
hypercautious European reaction to the Icelandic volcano in

We have since
that the maximum density of ash (100
micrograms of ash per cubic metre) over the UK during the ban was
one fortieth of that now
a safe threshold (4,000 micrograms of ash per cubic metre). In
other words, the ban was nowhere near justified by what is now the
official threshold.

He goes on to give some remarkable numbers from the similar
over-reaction to avian flu:

Take the response to the avian flu
outbreak in 2005. Dr David Nabarro, the UN systems coordinator for
human and avian influenza,
: ‘I’m not, at the moment, at liberty to give you a prediction on
[potential mortality] numbers.’ He then gave a prediction on
potential mortality numbers: ‘Let’s say, the range of deaths could
be anything from five million to 150million.’ Nabarro should have
kept his estimating prowess enslaved: the number of cases of avian

at a mere 498, of which just 294 have
proved fatal.

And swine flu:

On 11 June 2009, just over a month after
the initial outbreak in Mexico, the World Health Organisation
finally announced that swine flu was now worthy of its highest
alert status of level six, a global pandemic. Despite claims that
there was no need to panic, that’s exactly what national health
authorities did. In the UK, while the Department of Health was
closing schools, politicians were falling over themselves to
imagine the worst possible outcomes: second more deadly waves of
flu, virus mutation – nothing was too far-fetched for it not to
become a public announcement. This was going to be like the great
Spanish Flu pandemic of 1918-20. But worse.

However, just as day follows nightmares,
the dawning reality proved to be rather more mundane. By March
2010, nearly a full year after the H1N1 virus first began
frightening the British government, the death toll stood not in the
hundreds of thousands, but at 457. To put that into

the average mortality rate
for your common-or-garden
flu is 600 deaths per year in a non-epidemic year and between
12,000 and 13,800 deaths per year in an epidemic year. In other
words, far from heralding the imagined super virus, swine flu was
more mild than the strains of flu we’ve lived with, and survived,
for centuries. Reflecting on the hysteria which characterised the
WHO’s response to Mexico, German politician Dr Wolfgang Wodarg

the WHO last week: ‘What we experienced in Mexico City was very
mild flu which did not kill more than usual – which killed even
less than usual.’

In the same vein, I am wont to remind people of how `hundreds of
thousands’ of Britons were going to die of new variant CJD, the
human form of mad cow disease. In fact the number of deaths never
exceeeded 28 a year, has now fallen to 3 last year, one the year
before, and the total is just 168. By all means let us be cautious,
but can we not also treat extreme predictions about disease (or
climate or pollution or anything else) with a little caution


By Matt Ridley | Tagged:  rational-optimist