Outbreak of Shiga toxin-producing E. coli O104 (STEC O104:H4) Infections Associated with Travel to Germany (FINAL UPDATE)

Posted July 8, 2011

Outbreak Summary

CDC is monitoring a large outbreak of Shiga toxin-producing Escherichia coli O104:H4 (STEC O104:H4) infections ongoing in Germany. The responsible strain shares virulence characteristics with enteroaggregative E. coli (EAEC).  As of July 5, 2011, case counts confirmed by Germany’s Robert Koch Institute include 852 patients with hemolytic uremic syndrome (HUS)–a type of kidney failure that is associated with Shiga toxin-producing E. coli, or STEC, infections–and 32 HUS-associated deaths.

In the United States, six confirmed cases of STEC O104:H4 infections have been identified. Of these six cases, five recently traveled to Germany, where they were likely exposed. Bacterial isolates from four HUS cases reported in Arizona (1), Massachusetts (1), Michigan (1) and Wisconsin (1), and two cases with diarrheal illness reported in Michigan (1) and North Carolina (1), have all been confirmed as matching the outbreak strain. One death has been reported in the Arizona resident with HUS who traveled to Germany before becoming ill. The Michigan resident with diarrheal illness did not travel to Germany, but likely acquired this infection through close contact with the Michigan resident with HUS. 

Among U.S. military personnel and their dependents that are stationed in Germany, there are no confirmed cases at this time. Continuous monitoring has shown no increase in visits due to gastrointestinal illness at U.S. military medical treatment facilities in Europe.

CDC has alerted state health departments of the ongoing outbreak and requested information about any persons with either HUS or Shiga toxin-positive diarrheal illness, with illness onset during or after travel to Germany and since April 1, 2011. Additionally, CDC is working with state health departments to learn more about suspect cases and obtain bacterial isolates for further characterization. When a report of STEC infection is investigated, every effort is made to identify ill family members or other close contacts to determine if person-to-person spread has occurred. With this outbreak, only one instance of person-to-person spread has been documented in the United States.

Investigation of the Outbreak

RKI, the Federal Institute for Risk Assessment, and the Federal Office of Consumer Protection and Food Safety have found substantial epidemiologic and traceback evidence indicating that fresh sprouts produced by a farm in Lower Saxony are responsible for the current outbreak in Germany. German public health authorities currently recommend that people in Germany not eat raw sprouts of any origin. Traceback investigations of the food chain indicate that no sprouts or other food items from the implicated farm in Lower Saxony have been exported outside Germany. Travelers to Germany should be aware that the recommendation not to eat cucumbers, tomatoes and leafy salads in northern Germany was lifted. On June 10, 2011, RKI announced that contaminated raw sprouts from one farm in Germany are the likely source of the outbreak. This farm has been closed and the sprouts produced there are no longer in restaurants or store shelves in Germany. Over the past few weeks, the number of cases associated with this outbreak has markedly decreased. While some cases may still occur because of the time it takes between when a person becomes ill and when the illness is reported, it is likely that the number of cases will continue to decrease until the outbreak is over.

On June 24, 2011, France reported a cluster of E. coli O104:H4 infections among persons who attended an event in Bordeaux, France. Attendees reported eating sprouts served at the event. The sprouts were privately produced in small quantities by the organizer of the event from seeds purchased locally in Bordeaux.

The European Food Safety Authority (EFSA) initiated a comprehensive investigation to identify the source of the two outbreaks. On July 5, 2011, EFSA issued a report of its findings. Comparison of information from the outbreak investigations led to the identification of a single lot of fenugreek seeds, from an exporter in Egypt, as the most likely source of the sprouts linked with the two outbreaks. Given the possible severe health impact of exposure to a small quantity of contaminated material, and in the absence of information regarding the source and means of contamination and possible cross-contamination, all lots of fenugreek seeds from the identified exporter should be considered suspect.

Although rare, E. coli O104:H4 has been identified before. For example, in 2009 in the Republic of Georgia, culture of specimens from two patients who were part of a cluster of diarrheal illness yielded an E. coli O104:H4 strain that was similar to the current outbreak strain. That strain produced Shiga toxin, but had a different molecular fingerprint and was less resistant to antibiotics than the current outbreak strain in Germany. No clear outbreak was identified in the Republic of Georgia, and no food was identified as a source of infections.

The STEC O104:H4 responsible for the German outbreak has several genetic factors that contribute to its ability to cause illness. One is its ability to stick to cells in the intestine and another is its ability to make Shiga toxin. These factors are already well known and occur in various strains of E. coli in nature. E. coli, like many other bacteria, exchange genetic material and there is no evidence to think that this strain has been modified intentionally. Because of minimal person-to-person transmission associated with this strain, there is also no evidence to indicate that it will cause a pandemic or spread around the world.

Clinical Features/Signs and Symptoms

Any person who has recently traveled to Germany or has been in recent contact with an ill person who has recently traveled to Germany and has signs or symptoms of STEC infection or HUS, should seek medical care. He or she should tell the medical provider about the outbreak in Germany and the importance of asking the laboratory to test a stool specimen for STEC. Symptoms of STEC infection include stomach cramps, diarrhea (which is often bloody), and vomiting. If there is fever, it usually is not very high. Most people get better within 5-7 days, but some patients go on to develop HUS—usually about a week after the diarrhea starts. Symptoms of HUS include decreased frequency of urination, feeling very tired, and losing pink color of skin and membranes due to anemia.

Key Resources

• The Lancet (abstract): “Characterisation of the Escherichia coli strain associated with an outbreak of haemolytic uraemic syndrome in Germany, 2011: a microbiological study”
• CDC E. coli Resources for Clinicians
• E. coli: Key publications
• MMWR - “Recommendations for Diagnosis of Shiga Toxin–Producing Escherichia coli Infections by Clinical Laboratories”
• FoodSafety.gov

CDC's Role in Food Safety

CDC leads federal efforts to gather data on foodborne illnesses, investigate foodborne illnesses and outbreaks, and monitor the effectiveness of prevention and control efforts. CDC is not a food safety regulatory agency but works closely with the food safety regulatory agencies, in particular, with the Food and Drug Administration of the U.S. Department of Health and Human Services and the Food Safety and Inspection Service of the U.S. Department of Agriculture. CDC also plays a key role in building state and local health department epidemiology, laboratory, and environmental health capacity to support foodborne disease surveillance and outbreak response. Notably, CDC data can be used to help document the effectiveness of regulatory interventions.