When there was this outbreak in Germany in 2011, the finger of blame was naturally pointed first at this EHEC O157:H7 strain, which is still the most common. However, after two weeks of investigation, it was revealed that a new strain of E. coli, O104:H4 was to blame. This previously almost unknown strain, unlike EHEC O157:H7, can only attach itself to the cells of human intestines and is not present in animals. These properties show that it is of human origin (See below “A new nomenclature to better trace the origin of the disease”). “This information was quickly ‘forgotten’. As a veterinary bacteriologist, I was annoyed at the fact that, in the case of an epidemic, the finger of blame is systematically pointed at animals, particularly when the symptoms suggest infection by the E. coli bacteria. I will concede that in the case of the O157:H7 strain, animal origin is not to be doubted as the cause. In other cases, the source is very different. I was determined to contribute to this article after reading a comment by a member of the public on the website of a Belgian television channel. A short while after the outbreak of the epidemic, a journalist announced that several French people had also been infected, but that it involved another strain of the bacteria. The individuals concerned had indeed eaten hamburgers. Therefore the journalist was right, yet one of the readers of the article made the following comment. ‘Another strain, come on, the scientists are taking us for idiots’. This comment perfectly demonstrates the kind of incomprehension that prevailed due to the fact that the problem had not been properly explained to the wider public”, laments the researcher.

From human to human via raw vegetables

It was difficult to identify the source of the outbreak, that is to say the actual food concerned, despite the fact that it seemed to be confined to Germany. The fact that cucumbers from Spain were blamed outright for the outbreak was clear proof of the difficulty in finding the culprit. “Epidemiological surveys pointed to this type of cucumber as the source of the contamination. However, this was only a suspected cause which for no apparent reason soon became accepted as an established fact and this was the first big mistake in contributing to the general confusion surrounding the epidemic.”

From an epidemiological point of view and after focusing on several possible sources, attention was turned to fenugreek seeds, a medicinal plant often found in raw vegetable dishes that were produced in Egypt and transited through England before ending up in Germany. “The most likely hypothesis is that a man carrying the bacteria came into contact with the vegetables at some point in the production chain. The cultivation of the fenugreek seeds in a propitious climate (temperature, humidity and organic production) favored the proliferation of the O104:H4 strain which caused infection when consumed by humans. Yet, although the epidemic affected several thousand people, it should be pointed out that, from an epidemiological viewpoint, it was an isolated incident, a one-off  accident. Once the source of the outbreak was identified and removed from the food-chain, the epidemic slowed down and eventually ended”. The fenugreek vegetable was therefore the intermediary vector from human to human and not between animals and humans. “It is a bacteriological nuance which appears simple once it is known, yet it is not yet understood by everybody, even among the medical community. Some still think that the fenugreek seeds were infected by fecal matter from cattle, for example.”

What makes the job of bacteriologists even more difficult is the fact that, although fenugreek was almost certainly the cause of the outbreak, this will never be established with full certainty. “It will almost certainly not be possible to isolate the bacteria from the infected seeds because it is present in such small quantities in the beginning. In bacteriology, when a diagnosis is made, the quantity of the pathogenic microbe is very significant. It can be found in humans because it multiplies massively but it is difficult and probably impossible to find it in a food-source such as fenugreek, at least in this case”, the researcher declares.