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

Updated June 23, 2011

Today's Highlights

  • As of June 22, 2011, Germany’s Robert Koch Institute (RKI)* reports 823 patients with hemolytic uremic syndrome (HUS)–a type of kidney failure that is associated with Shiga toxin-producing E. coli, or STEC, infections–and 29 deaths associated with HUS.
  • In the United States, five confirmed cases and one suspect case of STEC O104:H4 infection have been identified. One death has been reported in an Arizona resident who had recently traveled to Germany. This case has not yet been confirmed to have STEC O104:H4 and is currently under investigation.
  • 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.

Introduction

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 June 22, 2011, case counts confirmed by Germany’s Robert Koch Institute* include 823 patients with hemolytic uremic syndrome (HUS)–a type of kidney failure that is associated with Shiga toxin-producing E. coli, or STEC, infections–and 29 HUS-associated deaths.

In the United States, five confirmed cases and one suspect case of STEC O104:H4 infections have been identified; one death has been reported. Of these six cases, five recently traveled to Germany, where they were likely exposed. The bacterial isolates from the three HUS cases reported in Massachusetts, Michigan and Wisconsin, and two cases with Shiga toxin-positive diarrheal illness reported in Michigan and North Carolina, have been confirmed as matching the outbreak strain. The Michigan case with Shiga toxin-positive diarrheal illness did not travel to Germany, but likely acquired this infection through close contact with the Michigan case with HUS. Arizona has reported one death in a HUS case with recent travel to Germany. This case has not yet been confirmed to have STEC O104:H4 and is currently under investigation.

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. Trace back 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.

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. More information about the characteristics of the STEC O104:H4 strain can be found in The Lancet (abstract) - “Characterisation of the Escherichia coli strain associated with an outbreak of haemolytic uraemic syndrome in Germany, 2011: a microbiological study” and in The New England Journal of Medicine - "Epidemic Profile of Shiga-Toxin–Producing Escherichia coli O104:H4 Outbreak in Germany — Preliminary Report".

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

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.

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