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Jeremy Laurance: Let down by the reality of swine flu

We have to explain that science deals in probabilities, not certainties

Forgive me if this sounds callous, but I am finding it hard to conceal my disappointment about swine flu. For years I have been writing about the "next flu pandemic" and its potential to cause catastrophe, on the basis of what virologists told me.

I went to Hong Kong in 2003 to report on the outbreak of Severe Acute Respiratory Syndrome – better known as SARS – because I thought that might be it. I followed the spread of avian influenza from the Far East across Europe to Britain in 2006 with, yes, eager anticipation. And when swine flu broke out in Mexico last April and the first flu pandemic in 40 years was declared, I sounded the alarm as loudly as anyone.

I didn't expect it to end with a whimper instead of a bang. But that is how it is looking now – for this year at least. New infections have plateaued for the last two weeks at levels only just above the baseline for seasonal flu. The official reason given is the "half-term effect": children off school slow the spread of the virus. But swine flu may well now be on a downward trend. Flu outbreaks happen in waves of up to 16 weeks, and more usually 10 weeks. We are already in week 10 of the current wave.

Of course, it is still early days. Even if we are over the worst for this year, the virus may mutate and come back in a third wave (the first happened in the summer) later this winter or next. But suppose it does not. What then? How will Sir Liam Donaldson, the Government's chief medical officer, and the virologists that advise him explain the enormous resources – £1bn plus – that have been devoted to fighting what will have turned out to be a not very great threat?

Swine flu is very nasty in a few people – especially under-fives, pregnant women and those with chronic illnesses. It has killed perfectly healthy young people. In this respect it is significantly different from seasonal flu which mainly kills the vulnerable elderly. Even so, the Government's worst-case scenario for this year – the worst case – is 1,000 deaths. When I wrote my first story warning of the threat of pandemic flu exactly 20 years ago, in the midst of the 1989-90 seasonal flu epidemic, 35,000 people died in Britain.

I have great sympathy for Sir Liam Donaldson. The one thing we know about flu is its unpredictability. Calling the odds on the extent and severity of a flu pandemic is an impossible task. Yet in speaking to virologists in recent days, I sense a certain defensiveness, a reluctance to accept that, potentially, we may have overdone it on flu.

That should not be surprising. If I feel disappointed – and, ghoulishly, I do – how much more disappointed must be those who have devoted their life's work to pandemic flu? They may feel relief at the lives spared, while grieving for the research grants lost, and for their missed moment in the sun.

If the retreat of swine flu is confirmed this week, I worry what impact it may have on public confidence in science. We were warned to prepare for a modern plague. If it does not arrive, how closely will we heed future warnings? There is surely, then, only one option. To explain that science deals not in certainties but probabilities, that when things do not turn out as we expect we will endeavour to discover why, and to admit – ministers, officials, researchers and those who, like me, report their research – that on this occasion we got it wrong.

Jeremy Laurance is Health Editor of 'The Independent'