David Heymann
Head and Senior Fellow, Centre on Global Health Security

The current outbreak of a life-threatening strain of E. coli bacteria that is spreading across Europe and has ignited trade tensions is a reminder that the way we interact with animals can facilitate the emergence of dangerous infectious diseases, and that borders do not prevent their spread, nor the economic impact that can result.

The bacteria which scientists suspect may be a new variant of a rare strain, has killed 18 people so far and made more than 1,600 people in 12 countries ill, with many hospitalized and several requiring intensive care.

At the same time, economies in European countries that produce vegetables have felt the severe impact of trade barriers that have been imposed as initial precautionary measures based on understanding from similar outbreaks in the past.

While most E. coli bacteria are harmless and are commonly found in humans, a group called enterohaemorrhagic E. coli, which are normally found in the gut of animals such as sheep and cows, can produce toxins that damage human blood cells and kidneys. This type of E. coli is transmitted to humans primarily through consumption of contaminated foods such as raw or undercooked ground-meat products and raw milk, fresh fruits and vegetables, or through contaminated water, direct contact with animals or contact with infected people. Thorough cooking destroys the bacteria.

Investigators are working to identify the source of the outbreak and the World Health Organization is not recommending travel or trade restrictions, but is instead urging normal hygiene measures such as washing hands and food. But exports from Spain have markedly decreased because of an assumption German officials made that cucumbers grown in Spain were the culprits. Germany later rescinded that statement after tests cleared Spanish cucumbers, but the economic damage had been done and Spain is now seeking compensation and threatening to sue the German authorities.

Trade tensions have been exacerbated by Russia's banning of fresh vegetable imports from the EU, despite the UN health agency advising that no such measures are necessary - a move that senior EU health officials immediately objected to, saying such sanctions were unjustified, disproportionate and out of line with the principles of global trade agreements.

Precautionary measures are understandable -and advisable - when there is not enough evidence to allow authorities to match their responses to the level of threat. However, such measures should be adjusted once the evidence does become available. It is hoped this will be the case once investigators identify the source of the outbreak in Germany.

However, experience with past outbreaks shows that self-correction is difficult and often lags far behind the evidence. Far too often, precautionary measures imposed during times of uncertainty have not been adjusted when they are no longer appropriate from the health protection standpoint, and such failure has a severe impact on the economies and sectors affected.

For instance, banning British beef imports was a reasonable precautionary measure at the outset of the Mad Cow outbreak in the 1990s because it was unclear what the exact cause of the problem was. But even when experts had identified that cattle feeding and butchering practices were at fault, and the risk eliminated, the ban continued nonetheless, ravaging the beef industry for longer than was necessary.

Similarly, the slaughter of pigs in Egypt during the 2009-10 swine flu outbreak caused severe economic damage despite the evidence which clearly showed that the pandemic virus, could not be contracted by eating pork or touching pigs,

The E. coli outbreak in Germany will not be the last outbreak in which precautionary measures damage economies and industries, but it provides another test of our collective ability to appropriately adapt reactions according to the evidence so that the negative impacts on trade and industry are no greater than necessary.