2011 E. coli o104 : h4 outbreak in Germany and in France : lessons learnt In May/June 2011, two outbreaks of shigatoxin-producing Escherichia coli O104 : H4 were reported mainly in Germany, but also in France, and to a lesser extent in about fifteen other countries. The relative rarity of this bacterial strain, the difficulties of tracing it back to the food source, and the serious impact on consumer health are addressed in this thesis. Mis-communication to the general public had major economical consequences for the agricultural sector, as the contamination was initially attributed to a source later exonerated. The most likely source, based on the investigation of 41 patient cohorts, and the similarity of the bacterial strains in the German and the French outbreaks, is a batch of fenugreek seeds imported at the end of 2009 from Egypt. Finally, all concerned authorities learned from this serious crisis, responsible for over than 900 cases of haemolytic uraemic syndrome (HUS) and 55 deaths.