The European Food Safety Authority (EFSA) has published its fast track risk assessment on consumer exposure to STEC/VTEC (Shiga toxin or verotoxin producing E.coli) through the consumption of raw vegetables and provided advice on options to mitigate the risks of possible food contamination and human infection. The strain (STEC O104:H4) responsible for the current outbreak in Germany, although rare, is similar to strains that have been previously reported.
Currently, the route of exposure for the STEC outbreak in Germany remains unknown. While contamination of fresh vegetables with STEC is rare, it has been associated with some severe outbreaks, including the current outbreak in Germany. The European Commission has therefore requested EFSA to provide advice on the relative exposure of humans to STEC from surface or internal contamination of vegetables and from the handling of vegetables from the farm to the consumer. Due to limited information available regarding STEC in vegetables, EFSA scientists were unable to estimate the relative human exposure through these routes. With respect to risk mitigation, EFSA scientists highlight the importance of preventing contamination before and after harvesting.
EFSA’s scientists assessed that the strain responsible for the outbreak in Germany is similar to strains that have been previously reported. However, in the current outbreak, this strain is responsible for an unusually high number of people affected and an increased severity of illness. Infection with STEC can cause bloody diarrhoea and can lead to cases of haemolytic uremic syndrome (HUS) in humans; a systemic disease which can in some cases result in acute kidney failure and fatalities.
Humans can be exposed to STEC and eventually become infected through contaminated food and water, direct or indirect contact with animals or human-to-human contact. In this report, EFSA has specifically assessed possible exposure through vegetables.
In its exposure assessment, EFSA considered bacterial contamination on the surface as well as inside the vegetable both before and after harvesting. While the overall prevalence of vegetable contamination with STEC at EU level is very low, there is a growing number of reports in the international scientific literature of STEC outbreaks associated with vegetables, particularly sprouting seeds and green, leafy salad vegetables. Contamination occurs mostly on the surface of plant tissues. However, internal contamination, such as through the root of the plant, cannot be ruled out although the data to support this are very limited and of an experimental nature.
As requested by the European Commission, EFSA’s scientists make recommendations for mitigating the possible risks of food contamination and human infection from STEC. EFSA confirms existing advice on the importance of following good agricultural practices, and good manufacturing and hygiene practices as laid down in internationally recognised guidelines.
In addition to this work, EFSA is supporting the STEC outbreak investigation by providing senior scientific staff with expertise in data collection, and epidemiological analysis including foodborne outbreaks. Furthermore, later today the Authority will publish a technical report jointly with the European Centre for Disease Prevention and Control (ECDC) on the prevalence and incidence of STEC in humans, food and animals. This work is based on data supplied by EU Member States annually to the European Commission, ECDC and EFSA as well as data from the current STEC outbreak investigation.
The main focus in mitigating risks of food contamination and human infection from STEC should be on the prevention of contamination before and after harvesting.
Advice on mitigation options include:
- pre-harvest -- Good Agricultural Practices include avoiding access of farm animals to immediate environment of fresh produce; use of irrigation water of adequate microbiological quality; control sourcing, handling, treatment of manure.
- post-harvest --, The application of mitigation strategies reflected in Good Manufacturing Practices and Good Hygiene Practices in line with codes available from international organisations is recommended. In particular, the use of water of adequate microbiological quality during further processing; basic training on food hygiene practices to food handlers; adequate design and hygiene management of food premises including pest control plans; and the correct management of the cold chain. When food contamination occurs, the only effective method of eliminating STEC is to introduce a bactericidal treatment, such as heating (e.g. cooking or pasteurisation) or irradiation.
- advice on good hygiene practices for caterers and in the home -- washing hands before and after preparing foods, washing all fruit and vegetables, avoiding cross contamination, keeping storage temperatures low for food. Peeling and cooking fruit and vegetables can also remove microbes.
For more information on consumer advice:
 A similar E.coli O104:H4 strain was previously observed in Germany 10 years ago in a patient suffering from haemolytic uremic syndrome (HUS) caused by STEC infection. The current outbreak shares characteristics of strains of STEC which usually originate from animals and of EAEC (Enteroaggregative E.coli) which usually originates from humans.
 Prevalence is defined as the total number of cases in a population over a certain period of time whereas incidence refers to the number of new cases in a given period of time.