E coli food-poisoning outbreak shows how fear can triumph over reality

The gulf between our fears and the facts of this E coli story may put us in greater danger, says risk consultant David Ropeik
E coli outbreak: Spaniards demonstrate that eating their cucumbers is safe
Inflated fears over E coli poisoning in Germany are endangering the livelihoods of farmers and future health of many more people. Photograph: Carlos Barba/EPA

The outbreak of foodborne disease in Europe offers an interesting lesson in the psychology of risk perception. To be sure, the danger from this outbreak is real. It has killed 18 people so far and infected more than 2,000, hundreds of whom may suffer lifelong kidney damage. Cases have been recorded in 10 countries, but all were infected in northern Germany. In addition, this appears to be a new and more dangerous strain, a reminder of the constant battle medicine and public health must wage against the phenomenal ability of germs to mutate to resist our controls.

Certainly this risk is far more real than, say, the hypothesised human health risks from GM foods, or the disproved risk that vaccines can cause autism – other threats that demonstrate how our response to risk is more emotional than evidence-based. The number of dead and ill from this foodborne disease outbreak is already higher than the likely long-term mortality and morbidity caused by the Fukushima nuclear power plant accident in Japan, based on what we know so far about the dosages of radiation released (though that event is still unfolding).

But the actual danger for any vegetable-eating European, even in Hamburg or other places where the cases have been concentrated, is low. Statistically. Scientifically. But then, we don't just use scientific evidence or statistical probabilities to figure out what's dangerous. Risk perception is a mix of facts and feelings, intellect and instinct, reason and gut reaction. And in many cases, the feelings/instinct/gut have the greater influence.

This is neither right nor wrong, smart or stupid, rational or irrational. It's simply the reality of how we go about protecting ourselves, using the few facts we have, and applying a set of instinctive risk perception "fear factors" that help us gauge, quickly and subconsciously, how scary those few hints and clues feel.

The problem is, as good a job as this instinctive system has done during human evolution, it can make mistakes. Dangerous mistakes. We can fear too much (vaccines), or too little (particulate pollution from coal-burning power plants), despite the available evidence, and our perceptions can create risks all by themselves. Excessive fear of vaccines is allowing diseases that had almost been eradicated to spread once more. Conversely, inadequate concern about coal-burning power stations has meant coal has been favoured over scarier nuclear power, risking sickness and death for thousands of people from particulate air pollution. Fukushima is now playing a powerful part in this retreat from nuclear power.

So watching this foodborne E coli outbreak unfold has been instructive. Why, if the actual risk for any given person is so low, does it feel so scary to so many? The study of risk perception has found that uncertainty raises fear. We are uncertain about this risk for two reasons. First, science doesn't have all the answers, about which foods are risky, where they came from and so on. Second, any invisible/odourless/tasteless risk like this that we can't detect with our own senses is scary because we don't know all we need to know to protect ourselves. And in this case there is great uncertainty because of the unknown nature of the organism, and the difficulty in tracking down where it originated. That's a lot of unknowns, which make the risk scarier.

If you think a risk can happen to you, it doesn't matter what the numbers say. Many risk communication experts work hard to find clearer ways to help people understand risk numbers, as though that will make us think about those numbers more rationally, but if a risk is only, say, one in a million, but you think you could be the one, you are likely to worry at least a little, because your job is to keep yourself alive, not the other 999,999.

High awareness also increases fear. Subconsciously, the danger-detection systems in the brain give extra weight to information that's coming in all the time, or that can be readily recalled. This "availability heuristic" then feeds on itself in a positive feedback loop. We pay more attention to information that could mean we are at risk, and the media, in fierce competition with each other to bring us the information we want, feed this appetite, and feed our fears.

These are just three among many specific components of our instinctive risk perception system that can lead to the "perception gap": the gap between our fears and the facts. This gap presents its own, very real risks. In this case there are a lot of people who aren't eating vegetables – any vegetables. That's not good for their health. Hundreds of thousands of people are more worried than necessary, and more worried than normal, and chronic worry produces the myriad damaging health effects of stress (including a weakened immune system, which makes us more vulnerable to the very bacterial infections about which people are worried in the first place).

In addition, this outbreak will cost a huge amount of money, and damage the livelihoods and lives of thousands of people engaged in the produce and food industries across Europe.

I am not criticising people for being irrational about risk. Science has taught us just how inescapably instinctive and emotional the system is. But it is valuable to observe that the way we perceive and respond to risk can itself put us at risk. Understanding that, and understanding the specific elements that make a given risk more or less frightening than the facts alone suggest, is the first step toward avoiding the dangers of the "perception gap", and making healthier choices for ourselves and for society.

David Ropeik is an instructor in the Harvard University Extension School and author of How Risky Is It, Really? Why Our Fears Don't Match the Facts