AC360° Web Exclusive: All risks are not created equal

Dr. Nathan Wolfe
Special to CNN

Last week I was stranded in London by Eyjafjallajokull. As I waded through the throngs at St. Pancras station in London hoping to catch one of the few seats available on the train bound for Paris, I thought back to the fear and disruption during the first days of the swine flu (A/H1N1) epidemic roughly a year ago.

Natural threats, whether they be eruptions or epidemics, have the potential to disrupt our lives, and as I watched the media report on the eruption and heard disgruntled passengers complain, it became clear that many saw these distinct natural events in a very similar light.

Almost to a person, my fellow stranded travelers felt that both Eyjafjallajokull and swine flu were examples of government and media hyper-responsiveness. Two events, over-blown by scientists, politicians, and journalists either focused on advancing their careers or covering their backsides. Most felt that neither the eruption nor pandemic was deserving of the inconvenience, fear, and economic disruption that they had caused.

The desire to put these kinds of events in the same category must be tempting. While responding to true threats is clearly important, in a globally interconnected and instantly informed world, there is too much risk ‘noise’ and many of the events labeled as threats come to nothing, so the fact that busy people say ‘here we go again’ and continue with their days is not surprising and perhaps on some level even rational.

Yet all risks are not created equal. The worst scenario in the case of Eyjafjallajokull would have likely been a single downed airplane. And while the loss of hundreds of lives is tragic, the response to that loss would have been clear and definitive: all planes would have been grounded until safety was assured. The loss of those lives would not have been in vain; they would have prevented further deaths.

Swine flu, on the other hand was a very different beast. In the minds of those of us who study epidemics, it was an amazingly powerful force of nature. H1N1 was a virus that went from infecting no one to infecting perhaps a quarter of the human population. Viral fireworks! And while it certainly did kill, the fact that it didn’t kill on a massive scale was simply good luck. Had H1N1 been even nominally more deadly (even much less deadly for example than H5N1, the bird flu) it would likely have been the biggest catastrophe of the decade, killing hundreds of thousands if not millions.

The difference between these threats is nicely encapsulated by a concept in epidemiology called the basic reproductive number or Ro. For any epidemic, Ro is simply the average number of subsequent infections that each new case results in. If, on average, each case of a new epidemic leads to more than one subsequent infection, the new epidemic has the potential to grow and if, on average, each case leads to less than one subsequent infections it will peter out. The elegant concept helps epidemiologists distinguish between epidemics likely to ‘go viral’ and those likely to go extinct. It’s basically a measure of scalability, and a threat like swine flu is highly scalable while an eruption clearly is not. And that these sorts of risks are being conflated is not only surprising, but also dangerous.

How risks are perceived is not a trivial matter. Take Eyjafjallajokull, for example. If the maximum realistic loss associated with travel is a single airplane, it must be weighed against the maximum possible losses associated with road accidents that will certainly increase as people drive instead of using relatively safe air travel. In the case of swine flu, on the other hand, the potential costs of not rushing to develop a vaccine or working to decrease transmission could have been global and catastrophic.

And risk literacy, the ability to distinguish between different levels of risk severity, is not something only for policy makers. Effective response to natural disasters depends on people and how well they follow instructions. The constant barrage of threats articulated by the media has lead to chronic risk habituation and the only way to break that log-jam is for people themselves to understand risk, and be able to assess the differences between different kinds of disasters and how best to respond to them.

Officials responsible for dealing with natural disasters of all sorts bemoan the lack of scientific literacy among the general public, feeling that if only people better understood the way epidemics, volcanoes or hurricanes worked they might better heed warnings. And that is likely true. But despite the noble objective of broad scientific literacy, we cannot wait for it to occur. What’s needed urgently is a much more narrow effort to increase risk literacy: the capacity for all people to understand the basic features of threats associated with true risk so they can best interpret risk noise and understand how to respond.

If we cannot accurately distinguish between the highly divergent risks that Eyjafjallajokull and swine flu hold for humanity, we are not well placed to respond to the next real threat when it occurs.