Why are pandemics so dangerous?

H1N1_influenza_virus1

It may have been four years ago, but the swine flu pandemic of 2009/10 is still fresh in our minds. For most of us, all we could do was watch from the outside as the pandemic unfolded – just keep reading the newspapers and washing our hands. That’s why it was so fascinating at the Imperial Festival to hear from someone who was working on the ‘inside’ of the H1N1 pandemic; someone who could give clear insights into the workings of the virus and the policy decisions it necessitated, as well as answer the key question of why the swine flu virus affected some people more than others.

If anybody could provide that level of insight, it would be Prof Peter Openshaw, who took to the floor on the Saturday of Imperial Festival 2014 to talk through what makes a pandemic so dangerous in his lecture entitled Spanish Flu to Swine Flu. Prof Openshaw is Director of the Centre for Respiratory Infection at the National Heart and Lung Institute, but despite his academic prestige he was quick to remind us that the “truth is never simple, even in science.”

He explained that pandemic flu remained the most significant civil emergency risk on the National Risk Register of Civil Emergencies in 2013 – even after the swine flu pandemic turned out be relatively mild. And while there has generally been a downward trend in mortality from pneumonia and influenza over the decades, the trend has flattened and mortality rates remain steady. Prof Openshaw explained that there has been an evolution of new flu strains – a “shuffling of the card deck” that has created new viruses.

Of course, it wouldn’t be a talk on pandemics without a few scary slides. The first scary slide was a fact about the 2005 H5N1 bird flu strain – of the 112 cases, 57 people died. That’s quite a concerning case fatality ratio, to say the least. The second scary slide was about a study by Ferguson et al. who used data from cell phones as a surrogate marker to trace how humans travelled around the UK. The study revealed potential human-to-human transmission and so modelled a hypothetical UK outbreak. Seeing the vast majority of the country covered in red markers by the end was certainly alarming!

But not to worry, for the UK has a phased pandemic plan in the event of such an outbreak – prepare and be ready, then contain the disease by slowing the spread and buying time, and finally treat the disease. This three stage plan was apparently put into practice in the 2009 swine flu outbreak, from the first case on 27 April 2009 through the first and second waves to the declaration that the pandemic was over in 2010.

While the swine flu pandemic is largely considered to have been mild, researchers noted something rather odd about it, and it was a key unknown that Prof Openshaw discussed in his talk: Why are some people affected mildly by the disease and others severely? The answer, explained Prof Openshaw, was found in the MOSAIC study, a large collaborative study he was involved in. The MOSAIC (Mechanisms of Severe Acute Influenza Consortium) study aimed to uncover the secrets of severe influenza by taking a huge range of factors into account – everything from the virus itself (including viral load and viral sequence) to factors to do with the host (the infected person). The study enrolled 255 patients with flu-like illness and, by collecting and examining extensive clinical information, discovered that the presence of a particular gene – IFITM3 – was a major risk factor for severe influenza. Bingo!

While Prof Openshaw made it clear that “the truth is rarely pure and never simple in influenza research,” the results of the MOSAIC study are certainly intriguing and one can only hope the findings will be put to good use as we prepare for what Prof Openshaw calls “the next big one.”

The talk ‘Spanish Flu to Swine Flu’ took place on 10 May 2014 at Imperial College London as part of the Imperial Festival. View a video of the talk below.

 

IMAGE: Wikicommons

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