The World Health Organization said June 3 that the number of cases of hemorrhagic diarrhea and hemolytic uremic syndrome due to infection with a dangerous and possibly novel Escherichia coli serotype continues to climb, mainly in Germany.
Since the outbreak began in early May, 1,823 cases of enterohemorrhagic E. coli, or EHEC, have been reported altogether. There have been 552 cases of hemolytic uremic syndrome, or HUS, a dangerous nephrologic complication, and 18 fatalities.
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Germans have been advised not to eat raw tomatoes, cucumbers, or lettuce during the E. coli outbreak.
Most of the morbidity and mortality – 1,733 total cases, 520 HUS cases, and 17 deaths – has occurred in Germany alone, WHO said in an epidemiologic update published June 3.
At a separate June 3 briefing, U.S. health officials sought to reassure Americans that there is no reason to believe that the EHEC virus will spread to the United States.
The strain causing illness in Europe, STEC O104:H4, “is very rare,” said Dr. Chris Braden, director of Foodborne, Waterborne, and Environmental Diseases at the Centers for Disease Control and Prevention.
“The CDC is not aware of any confirmed cases of this infection ever reported in the United States," Dr. Braden said during a press briefing. "However, we have become aware of some similar strains that have been identified in other countries in the world in the past.”
There are currently four suspected cases of this infection in the United States, Dr. Braden said. Each suspected case has been identified in persons who traveled to Hamburg, Germany, in May 2011. “In the other countries outside of Germany in Europe and in the United States, the persons who became ill were exposed in Germany and became ill in their home countries after exposure,” he said. “We are continuing to monitor these cases closely. The risk of person-to-person transmission is low.”
The CDC is working with state health departments to learn more about these suspected cases and to obtain bacterial isolates “for further characterization.”
Dr. Braden noted that there are no confirmed cases of STEC infection among U.S. military personnel or their dependents at this time. However, two service members in Germany with diarrheal illness are being evaluated as suspect cases.
The CDC will provide updates on the situation at www.cdc.gov/ecoli.
The German case count jumped dramatically since the beginning of the week, with 50 new cases of HUS and 149 cases of EHEC reported to national health authorities since May 31; however, a public holiday June 2 may have depressed notifications, and officials at the Robert Koch Institute (RKI) in Berlin acknowledged that the true count may be higher.
The rare shiga toxin–producing strain of E. coli responsible for the outbreak has been variously reported as novel and previously isolated, though it is not known to be responsible for any prior outbreaks.
The Robert Koch Institute, Germany’s national epidemiologic agency, emphasized in a statement June 3 that the causative agent, the STEC O104:H4, was not entirely new, as has been reported, though it had never before been responsible for an outbreak.
The previous day, BGI-Shenzhen, a genomics institute based in Shenzhen, China, had claimed that its sequencing efforts, on samples received from European health agencies, had revealed the agent to be "an entirely new super-toxic E. coli strain."
The disease-causing strain, BGI said on its website, "shares 93% sequence similarity with the EAEC 55989 E. coli strain, which was isolated in the Central African Republic and known to cause serious diarrhea," but with new sequences that may be involved in the pathogenicity of hemorrhagic colitis and HUS. The serogroup, BGI said, "carries several antibiotic resistance genes, including resistance to aminoglycoside, macrolides and beta-lactam antibiotics."
Though cases have now been reported in 12 European countries and the United States, nearly all have occurred among people with recent travel to northern Germany or who received visitors from that region. As of June 2, a majority of patients were aged 20 years or older (88%) and female (71%), a pattern departing from typical E. coli outbreaks, according to a June 2 update by scientists at RKI (Euro Surveill. 2011;16(22):pii=19883).
RKI is now conducting seven studies on the outbreak, including case-control studies in heavily affected hospitals; investigation of human-to-human transmission and food purchases made, by analysis of receipts, within the setting of an outbreak site; cohort investigations of groups in which members developed symptoms after dinner in a restaurant; exploration of several events and festivities potentially related to cases; and collecting data from nephrologists treating HUS cases.