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New epidemiological data corroborate existing recommendation on consumption by BfR

14/2011, 03.06.2011

Joint Press Release of the Robert Koch Institute (RKI) and the Federal Institute for Risk Assessment (BfR)

The Federal Institute for Risk Assessment (BfR) continues to recommend, by way of precaution, not to consume tomatoes, cucumbers and salads raw. This advice, which concerns more particularly products available in Northern Germany, is confirmed by the results of two new epidemiological studies of the Robert Koch Institute. The number of HUS patients per 100,000 inhabitants amounts in the Laender most severely affected to 5.5 for Hamburg, 5.1 for Schleswig-Holstein, 3.3 for Bremen and 1.8 for Mecklenburg-Vorpommern. In the cases in the other Laender a link to Northern Germany can be mostly observed.

Within the scope of the investigations on the EHEC/HUS outbreak event, the Robert Koch Institute conducts further epidemiological studies, including case control studies, online enquiries and a tracking and tracing of individual unusual outbreak events (cf Epidemiological Bulletin 22/2011). For two of these studies first results are now available.

In a case control study 46 female and male patients with HUS or EHEC infection were asked in Bremen, Hamburg and Lübeck from 29 May to 2 June 2011 to provide detailed information on foods consumed, including foods which had not yet been included in the study conducted in Hamburg and already published on 25 May 2011. These results were compared to those of 2100 healthy control persons of the same gender, age group and the same residential area. Whereas 84 % of the patients had consumed salad, this percentage amounted only to 47% for the healthy control persons. In the same way the share for the consumption of cucumbers was 75 % for patients versus 50 % for healthy controls, and for tomatoes the numbers were 80 % for patients versus 63 % for healthy controls. Overall, 95 % of the patients had consumed at least one of the three vegetable types. Statistical calculations of these data showed that the consumption of raw tomatoes, cucumbers and salads continues to be significantly associated with the HUS disease.

In a joint study on an accumulation of cases with the Frankfurt Health Office and the Hessian Land Testing and Investigation Office for the Health Care Sector in a company in Frankfurt, it was established that the employees who had consumed salad from the salad counter of the cafeteria suffered almost 7 times as often from bloody diarrhoea than employees who had not consumed salad. Other foods that were analysed did not show such a relationship.

The two independent studies, based on different methodologies, support the results of the first case control study whose results were presented on 26 May 2011. From an epidemiological point of view it can, therefore, be stated that the consumption of salads, tomatoes and/or cucumbers from Northern Germany continues to be the relatively highest risk for the cases of illness. The recommendation on consumption of the Federal Institute for Risk Assessment, therefore, continues to apply until epidemiological studies and investigations in foods will provide new information, the pathogen source has been identified or no new patients fall ill. 

Since the beginning of May 2011 an increasing number of persons have suffered from bloody diarrhoea and the so-called haemolytic-uremic syndrome (HUS). A total of 520 HUS cases have been reported to the Robert Koch Institute since the beginning of May 2011, including 11 cases of death (status: 2 June 2011, 3pm). 1,213 cases with an EHEC infection have been reported to RKI since the beginning of May 2011. Six of the patients died in the meantime.

HUS is a severe, under certain circumstances lethal complication, which can occur in connection with bacterial intestinal infections with so-called enterohaemorrhagic Escherichia coli (EHEC). Approximately 1,000 EHEC cases per year are reported to RKI. The complete clinical picture of the HUS is characterised by acute renal failure, anaemia due to the decomposition of red blood cells and a deficiency of blood platelets. In 2010 two cases of death were reported to the Robert Koch Institute.

The EHEC bacteria causing the HUS are transmitted directly or indirectly from animals to humans. Ruminants, mainly cattle, sheep or goats, are considered as reservoir. The transmission to humans occurs faecally-orally: the pathogen is taken up via the contact with animal faeces, via contaminated foods or water, but also via direct contact from humans to humans (smear infection).

Against the backdrop of the severe infection outbreak in May 2011, it is recommended, by way of precaution, not to consume non-heated types of vegetables which are suspected of being the cause of the infection (tomatoes, cucumbers and salads) and have been purchased in Northern Germany, until the identification of the precise cause of the outbreak. Already low germ counts are sufficient for an infection, so that a transmission is very easily possible.

Vegetable types, which are not suspected of being a cause of the infection, must be washed thoroughly prior to consumption (at least 30 seconds with strong rubbing, possibly with hot water) and, if necessary, be peeled. Washing and peeling of vegetables results in a reduction of the germ count and hence reduces the risk of infection.

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About BfR

The Federal Institute for Risk Assessment (BfR) is a scientific institution within the portfolio of the Federal Ministry of Food, Agriculture and Consumer Protection (BMELV). It advises the Federal Government and Federal Laender on questions of food, chemical and product safety. BfR engages in own research on topics that are closely linked to its assessment tasks.