Sprouts linked to European E coli outbreak

Jun 5, 2011 (CIDRAP News) – German officials today announced that they have tentatively linked bean sprouts grown in the northern part of the country to a massive Escherichia coli outbreak, a development that US experts say could help explain some of the outbreak's puzzling elements.

At a news conference today, officials from Lower Saxony state said initial tests have confirmed that bean sprouts are the likely cause of the outbreak, the Associated Press (AP) reported.

In other outbreak developments over the weekend, German authorities are investigating if a Hamburg harbor festival that took place May 6 to 8, drawing more than 1.5 million visitors from Germany and other countries, may have played a role in the spread of the disease, Agence France-Presse (AFP) reported yesterday. Also, officials are investigating illness clusters at two restaurants in Lubeck, located 40 miles from Hamburg.

The European Centre for Disease Prevention and Control (ECDC) today said it has received reports of 1,605 enterohemorrhagic E coli (EHEC) O104:H4 infections and 658 cases of hemolytic uremic syndrome (HUS). HUS is a potentially fatal kidney condition that stands out in this outbreak because the proportion of cases has been far higher than typically seen in E coli outbreaks.

So far 22 deaths have been reported, 16 of which occurred in patients who had HUS.

The ECDC report also said that more than two thirds of cases have been in women. It said the "great majority" of cases have been in adults.

Gert Lindemann, the state's agriculture minister, told reporters that different kinds of sprouts grown at an organic farm near Uelzen have been linked to infected patients in five different German states. He said investigators are looking at 18 different sprout mixtures, such as bean, broccoli, pea, chickpea, lentil, and radish.

Officials have shut down the farm and recalled the rest of its products, which include fresh herbs, fruit, flowers, and potatoes. Lindemann said at least one of the farm's employees had an E coli infection, the AP reported.

He said definitive test results will be available tomorrow and warned Germans not to eat sprouts until further notice, according to the AP. Authorities have still not ruled out other possible sources of the E coli outbreak strain, so Lindemann urged the public to continue to avoid tomatoes, cucumbers, and lettuce.

Another agriculture official added that the sprouts were delivered to many restaurants that have been linked to illness clusters.

The investigation of the E coli outbreak involving the extremely rare O104:H4 subtype surfaced in mid May and has stumped German health officials, who originally linked the outbreak to Spanish cucumbers, lettuce, and possibly tomatoes. The identification of the outbreak strain also sparked scientific debate over whether E coli O104:H4 is a new or unique strain.

US experts weigh in
While food safety experts wait for further test confirmation and more information on the lab results, some said the sprout source could explain some of the more puzzling aspects of the outbreak. Craig Hedberg, PhD, a foodborne disease expert at the University of Minnesota, told CIDRAP News that sprouts, if definitively identified as the source, would fit well with much of the other available data.

"They are a fresh produce item that would be more commonly eaten by women, and they are produced and distributed over a limited geographic area," he said. "Also the conditions needed to grow sprouts are perfect for incubating pathogens like EHEC. If these are bean sprouts, they are relatively large, and could have carried a relatively high dose."

Hedberg said it's unfortunate that the sprout connection wasn't identified sooner.

In the United States, alfalfa sprouts have been linked to several foodborne illness outbreaks. In 2009 the federal officials warned consumers not to eat raw alfalfa sprouts, including sprout blends, because they suspected alfalfa seeds used by the nation's sprout growers could be contaminated with Salmonella.

Michael Osterholm, PhD, MPH, director of the University of Minnesota's Center for Infectious Disease Research and Policy, publisher of CIDRAP News, said he's not surprised that sprouts appear to be the culprit, and that they should have been explored early on as one of the possibilities.

The outbreak's potential link to the Hamburg festival might explain the large numbers of patients with HUS, he said. "A festival setting could lead to the rapid dissemination of a pathogen like E coli in food, he said."The denominator may be extremely large."

"The festival gives that possibility, and we may find out that the E coli subtype is not more virulent," Osterholm said.

In 1988 an uncooked tofu salad served at a 5-day music festival in Michigan sickened 3,175 people with shigellosis, according to a report on the outbreak that appeared in the Mar 15, 1991, issue of the American Journal of Epidemiology.  The illness onset peaked 2 days after the festival ended, and sick patients were turning up throughout the United States by the time the outbreak was identified.

See also:

Jun 5 ECDC update

1991 Am J Epidemiol abstract

Jun 3 CIDRAP News story "Four US cases may be tied to European E coli outbreak"

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