Lessons cited as Germany declares end to E coli outbreak

Jul 27, 2011 (CIDRAP News) – Germany's infectious disease institute has declared that the Escherichia coli O104:H4 outbreak is over, now that the incubation period for the most recently confirmed case with links to the sprout seed–related event has passed.

The Robert Koch Institute, the county's federal disease control agency, released a statement in German yesterday saying that the 3-week incubation period had passed since the latest illness onset date—July 4—for a patient with an epidemiologic link to the outbreak, the European Centre for Disease Prevention and Control (ECDC) said today in its outbreak update. The agency said German officials are considering cases with onsets later than Jul 4 as having no epidemiologic links to the outbreak or no lab confirmation.

Because of reporting delays, additional cases are still slowly trickling into the ECDC. Health officials are also still sorting out confirmed and probable cases. So far the ECDC has received reports of 3,910 infections, including 782 with hemolytic uremic syndrome (HUS), a serious kidney complication. So far 46 deaths have been reported.

A few cases, most with links to German travel, were also reported in the United States and Canada.

The ECDC, in a Jul 8 risk assessment, warned that sporadic cases and new clusters would likely continue to be reported, because some of the contaminated seeds could still be on the market or in people's homes, cross-contamination during food handling could occur, and foodborne transmission could be linked to people with asymptomatic infections.

Craig Hedberg, PhD, a foodborne disease expert at the University of Minnesota School of Public Health, said that though the outbreak might be considered "over," there are still concerns about fenugreek seeds from potentially contaminated lots that have not been accounted for.

He said the outbreak has taught some useful lessons and raised some issues that warrant follow-up discussion.

European officials seemed in a rush to publish preliminary data that suggested the outbreak involved an unusually virulent enterohemorrhagic E coli (EHEC) strain when the full extent of exposure to the implicated food wasn't known, Hedberg said. "If we don't know the size of the denominator, the numerator is just a number."

Omitting sprouts in the original case-control study was an error that German health officials made and that led to the spurious association with cucumbers, lettuce, and tomatoes, Hedberg said. The same mistake has been made in other outbreaks elsewhere, he said, which should be a lesson for future outbreak investigations.

Hedberg said the reason given for omitting sprouts from the first case-control study was that fewer than half of the sick patients reported eating them. "This is not acceptable, because sprouts are a known previous vehicle, thus should have been part of any case-control study," he said. "And although they were reportedly eaten by fewer than half of cases, they were eaten by a higher proportion of cases than would have been anticipated, based on background rates of sprout consumption in the population."

See also:

Jul 27 ECDC outbreak update

Jul 8 ECDC risk assessment

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