Jun 3, 2011 (CIDRAP News) – The case count in Europe's unprecedented Escherichia coli outbreak climbed steeply again today as the number of potentially related cases in the United States rose to four, while a scientific debate continued on whether the outbreak strain, E coli O104:H4, is new or unique.
The World Health Organization (WHO) today put the total case count as of yesterday at 1,823, which includes 1,271 cases of enterohemorrhagic E coli alone and another 552 cases with hemolytic uremic syndrome (HUS), a potentially fatal type of kidney failure. The new total is up more than 200 from yesterday's WHO figure of 1,614 cases with 16 deaths.
The vast majority of the illnesses—1,213 EHEC cases and 520 with HUS—were in Germany.
"Between 31 May and 2 June, there have been 56 new cases of HUS (2 fatal) and 156 new cases of EHEC (2 fatal) reported globally," the WHO said.
At a US press conference this afternoon, Chris Braden of the Centers for Disease Control and Prevention (CDC) said there are now four cases in the United States suspected to be linked to the European outbreak. All are in people who recently traveled to Hamburg, Germany, the outbreak's focal point.
In addition, two US military personnel in Germany have diarrheal illnesses and are being monitored, said Braden, the CDC's director of foodborne, waterborne, and environmental diseases. Of the four domestic patients, three—two women and one man—have HUS and remain hospitalized, while the fourth person had bloody diarrhea but was not hospitalized, he said.
"At this time we see no reason to believe and no expectation that this will spread in our country," Braden said.
The source of the outbreak remained unknown today, though case-control studies in Germany have suggested cucumbers, lettuce, and tomatoes sold there as possible culprits. German public health officials maintained their warning to their compatriots to avoid those items. Early tests suggested Spanish cucumbers as the source, but further tests showed the cucumbers didn't carry the outbreak strain.
US Food and Drug Administration (FDA) officials at today's press conference said that very little fresh produce is imported from Spain and Germany, and the FDA will test any shipments of the suspected vegetables from those countries before allowing them to reach US stores.
Germany and Spain account for less than 0.2% of all fresh produce imported into the United States, said David Elder, the FDA's director of regional operations. He said the FDA's testing method for E coli in and on fresh produce takes about 7 days.
Don Kraemer, deputy director of the FDA's Center for Food Safety and Applied Nutrition, noted that the FDA offers guidance to help the food industry reduce the risk of produce contamination and is working on stronger safeguards. The latter include a new requirement under the Food Safety Modernization Act for all food processing facilities to develop preventive controls, and a produce safety regulation based on the existing voluntary guidance. The preventive-controls requirement should be ready by the end of this year and the produce safety rule by the end of 2012, he said.
Braden offered some new details about E coli O104:H4, which a team of Chinese and German researchers yesterday described as "entirely new" and "super-toxic." He said it differs from many other pathogenic E coli strains but that similar strains have been seen a time or two before.
"This particular strain of Shiga toxin–producing E coli [STEC] does differ from many of the other strains . . . in its genetic markers and, in a related way, how it, for instance, attaches to the lining of the intestine," he said. He said it is similar to the strains known as enteroaggregative E coli [EAEA], which, according to other experts, cause diarrhea but not bloody diarrhea or HUS.
Clinically, the outbreak strain seems to have a longer incubation period than other STEC strains, Braden said. "We've seen incubation times of over a week and maybe up to 12 days," he said. Incubation times for pathogenic E coli strains usually range from 1 to 8 days, according to reference sources.
In 2009, Braden said, the CDC helped the ministry of health in the Republic of Georgia investigate an outbreak of HUS and bloody diarrhea. "The organism we think was responsible for that was very similar to this organism that we're seeing now in Germany," he said. "It had much the same virulence profile. We never were able to identify a source."
In addition, a case of HUS attributed to E coli O104:H4 was reported in South Korea in 2006, Braden said, adding, "We've seen similar strains in other parts of the world. It's rare and we haven't seen much of it."
The outbreak strain's normal host or reservoir remains unclear, he noted.
The claim that the outbreak strain is brand new and "super-toxic" came yesterday from BGI, or Beijing Genomics Institute, in China, which worked with a German team to analyze the organism. In a related development, a US company, Life Technologies Corp. of Carlsbad, Calif., also claimed yesterday that the pathogen is new.
The company said preliminary results of DNA sequencing of the pathogen strongly suggest that it "is a new hybrid type of pathogenic E. coli strain." The analysis shows that the organism has genes from both enteroaggregative and enterohemorrhagic types of E coli. The company said it collaborated on the research with the University Hospital Muenster in Germany.
In contrast, Germany's Robert Koch Institute (RKI) today quoted a German expert as saying that the outbreak strain is not new. The RKI said Professor Helge Karch, director of the HUS Consultant Laboratory in Muenster, published information stressing that "reports stating that the current pathogen is a completely new strain are not correct." The RKI offered no further details.
Detecting non-O157:H7 strains
In response to questions at today's press conference, David Goldman of the US Department of Agriculture (USDA) declined to say whether the current outbreak will speed up the USDA's move toward declaring non-O157:H7 E coli strains adulterants in meat. He acknowledged that such a rule is under review at the Office of Management and Budget (OMB) but said it does not cover the European outbreak strain.
Goldman said the administration doesn't comment on the status of rules before their release, but OMB "is working closely with USDA and other agencies on this pending rule." Food safety advocates have been urging the USDA for sometime to classify pathogenic non-O157 strains as adulterants and test for them.
Jun 3 WHO statement
Jun 2 CDC statement on the outbreak
Jun 2 Life Technologies press release (translated)
Jun 3 European Centre for Disease Prevention and Control statement