Time is running out for German investigators to find the source of the world's deadliest E. coli outbreak, which has left more than 2,000 in Germany ill according to the country's national disease control centre.
Infectious disease expert Dr. Neil Rau says it can be very difficult to find the source when foodborne illness outbreaks aren't traced to a single meal. As time goes on, the contaminated food can make its way through the food system and be gone forever, even while sick patients are just beginning to make their way to hospital.
It's then difficult to link patients to contaminated produce weeks after they first became infected, because new batches of the same food will test clean.
"With a lot of these outbreaks, by the time investigators get into the investigation mode, the evidence is rapidly disappearing," he told CTV News Channel Tuesday.
For that reason, he says, "We may not actually get the answer we're all waiting for."
The other reason food poisoning outbreaks are difficult to investigate is because the illness can incubate for 3 to 10 days before causing symptoms.
By the time patients are asked about what they recently ate, it becomes difficult to remember. And with the outbreak now in its fourth week, investigators could be re-interviewing people about foods they ate up to a month ago.
Dr. Guenael Rodier, director of communicable diseases expert at WHO, agrees that time is running out.
"If we don't know the likely culprit in a week's time, we may never know the cause," he told The Associated Press on Tuesday.
Tests are continuing on sprouts from an organic farm in northern Germany, but have so far come back negative. But Rodier said that doesn't necessarily exonerate the vegetables.
"Just because tests are negative doesn't mean you can rule them out," he said. "The bacteria could have been in just one batch of contaminated food and by the time you collect specimens from the samples that are left, it could be gone."
Meanwhile, the illnesses continue to mount. The number of people who have fallen ill in the E. coli outbreak in Germany rose Tuesday to 2,325, according to the country's national disease control centre.
The Robert Koch Institute says 94 more people have been infected. The death count remains at 22: 21 Germans and one Swede.
The institute says the latest figures suggest that the number of new cases is declining -- a sign the epidemic might have reached its peak. But it cautions that it is not certain whether the latest decrease will continue in the coming days.
The death count could still rise because 642 are currently suffering from a serious complication, called HUS (hemolytic uremic syndrome), which causes the kidney to shut down.
Women make up the majority of the cases. It's thought that that's because they tend to eat more of the fresh produce suspected in this outbreak.
EU health chief John Dalli is warning Germany against making inaccurate conclusions on the source of the contaminated food.
Dalli told the EU parliament in Strasbourg that information from health officials must be scientifically sound and foolproof before it becomes public.
"It is crucial that national authorities do not rush to give information on the source of infection that is not proven by bacteriological analysis, as this spreads unjustified fears (among) the population all over Europe and creates problems for our food producers," Dalli said.
Over the past few weeks, Germany has pointed a finger at Spanish cucumbers, then at local sprouts, before backtracking on both.
Germany's agriculture minister, Ilse Aigner, defended the country's warnings on Spanish cucumbers and local bean sprouts, saying both issues were suspicious enough to be alerted.
With reports from the Associated Press
