Jun 1, 2011 (CIDRAP News) – The count of cases and deaths in Europe's Escherichia coli outbreak pushed higher today, with various news reports citing about 1,500 cases and 17 deaths, while the source of the epidemic remained a mystery.
Official figures from European authorities didn't all agree but remained considerably lower than those from news services. The European Commission (EC) in a May 31 release listed a total of 1,245 cases and 10 deaths in nine countries, with the vast majority of cases in Germany. It cited 399 cases of hemolytic uremic syndrome (HUS), the potentially fatal kidney disorder associated with some E coli infections.
Today, Germany's Robert Koch Institute (RKI) put the number of HUS cases in Germany at 470, with 9 deaths. The EC statement agreed that Germany had 9 fatal cases and said the other death was in Sweden.
The RKI repeated German authorities' advice not to eat raw tomatoes, cucumbers, and lettuce, especially those acquired in northern Germany, the center of the outbreak. The warning will remain "while the outbreak investigations continue as long as the source of the infection has not been identified," the institute said.
A case-control study by German officials last week pointed to cucumbers, tomatoes, and lettuce as possible sources of the outbreak, and pathogenic E coli was found on four cucumbers, three of them from Spain. But today the EC said further tests showed that the Spanish cucumbers did not carry the outbreak strain, E coli O104. "Despite the fact that some of the sampled cucumbers did test positive to STEC [Shiga toxin–producing E coli], the tests did not confirm the presence of the specific serotype . . . affecting humans," the EC said in a statement.
Of the 1,245 total cases listed by the EC, 1,169 were in Germany. Sweden had 41 cases and Denmark 14, with a few cases each in the Netherlands, France, the United Kingdom, Austria, and Switzerland. Spain, said to be the source of three of the contaminated cucumbers, had just one case.
In the United States, the Centers for Disease Control and Prevention (CDC) yesterday reported two HUS cases in people who had recently traveled to Germany. It was still unknown whether those patients had the outbreak strain, a CDC official told CIDRAP News today.
While the European outbreak is clearly one of the largest on record, it is smaller than at least one other outbreak. In a 1996 episode in Sakai, Japan, 8,355 schoolchildren were sickened by eating radish sprouts contaminated with E coli O157:H7, according to a 1999 report in the American Journal of Epidemiology. The report did not list the number of deaths.
Also, the E coli O157:H7 outbreak in Walkerton, Ont., in 2000 was of comparable size with the European epidemic. Medical journal reports on the Ontario outbreak cite 1,436 cases, including 27 HUS cases, with six deaths, but also say total estimated cases exceeded 2,300. The outbreak was blamed on a city well that was contaminated by farm runoff.
The Japanese and Canadian outbreaks were both localized, unlike the European one, with cases in at least nine countries.
In a statement yesterday, the World Health Organization (WHO) said all but two cases as of May 30 were in people who had been in northern Germany. "One laboratory-confirmed case of EHEC [enterohemorrhagic E coli] infection with no apparent link to Germany or to other known cases was reported in Denmark, and in Norway there was a case where the patient had a visitor from Germany," the WHO said.
Disease experts have been perplexed by the high number of HUS cases reported in the outbreak and the finding that most are in adults. The WHO said 88% of HUS cases in Germany as of May 30 were in people at least 20 years old, most of them women. The agency noted that HUS predominantly affects children and said that up to 10% of EHEC patients may experience HUS, with a mortality rate of up to 5%.
Phillip I. Tarr, MD, an HUS expert at the Washington University School of Medicine in St. Louis, told CIDRAP News today that it's not clear how many of the reported HUS cases in Europe really are HUS.
"This is the fog of an outbreak. It's not clear that we have stringent case definitions," said Tarr, who is the Melvin E. Carnahan professor of pediatrics and directs the Division of Pediatric Gastroenterology and Nutrition at the school.
He said the deaths leave no doubt that severe cases are occurring. "Below that, it becomes murky as to how many patients are really meeting the case definition of HUS. We generally have used a fairly definable cut point by lab testing, and I think in retrospect we'll be able to confirm" the cases. But for now, the situation isn't clear, he said.
"The other thing we're not clear about is the denominator: how many people are culture-confirmed, highly credibly infected versus not so credibly infected," Tarr said. He said it's not known how many patients have undergone appropriate diagnostic testing, adding, "In many outbreaks—Walkerton, for example, and Sakai in Japan—microbiologically confirmed cases were really a small minority of the putatively infected group."
Tarr also noted that in E coli cases, antibiotic treatment seems to bring an increased risk of HUS, but said he had no information on the potential role of antibiotic treatment in the European outbreak.
"What is most important though, even with avoidance of antibiotics, is that patients be profiled at the point of presentation and ideally be hospitalized and intravenously hydrated," in line with guidelines for treating children with suspected E coli infection, he said.
More generally, Tarr commented, "This is one of the most lethal outbreaks I can recall. . . . The serotype is not one we would've predicted would've been the cause of something like this, and we're hoping the epi curve peaks soon if it hasn't already. But it does demonstrate the importance of microbiologic vigilance on the foods that are not subjected to bactericidal processes and the critical importance of good, comprehensive point-of-presentation microbiology."
May 31 EC statement
Jun 1 EC statement
May 31 WHO statement