Teams of scientists working around the clock across Germany, analysing food samples in the hunt to find the source of a deadly E coli outbreak, may labour for weeks only to hit a frustrating dead end.
Teams of scientists working around the clock across Germany, analysing food samples in the hunt to find the source of a deadly E coli outbreak, may labour for weeks only to hit a frustrating dead end.
Scientists say we may never know for sure whether it was mixed salad, Spanish cucumbers, organic bean sprouts or some other foodstuff that harboured a lethal strain of the bug that has infected more than 2,400 people and killed 23 of them.
Patience and caution are needed most. But they are in short supply given anxiety over the number of sick and with diplomatic and trade rows erupting across Europe.
"In the majority of cases in these outbreaks we never actually identify the source," said Brendan Wren, a microbiology professor at the London School of Hygiene and Tropical Medicine.
E coli bacteria thrive in nutrient-rich environments like the guts of humans or cows before being discharged. This strain has been found to be particularly sticky, making it likely to cling on to leaves, seeds and other foodstuffs.
But these bugs are also sensitive to the outside world, so a lack of nutrients or changes in temperature, salt concentration or PH levels could be enough to finish them off.
"It's a bit like a crime investigation -- it's very difficult to find the offending organisms because they can disappear as time goes on," said Wren.
Yet several factors in this outbreak, centred around Hamburg in northern Germany, give scientists a little more hope.
Those affected are many, and the infections are mostly in, or linked to, one area of Germany and mostly in younger women, which should make it easier for investigators to home in on common denominators.
Anthony Hilton, a microbiologist at Aston University, points out that because this particular E coli strain is rare, "that may actually help in the investigation to determine the origin".
"Nevertheless it may be some time, if at all, (before) we are able to pinpoint this with any certainty," he said.
For consumers, farmers and politicians, the damage to confidence and trade relations could linger for months if no precise source is found.
But Stephen Smith, a microbiologist at Ireland's Trinity College Dublin, said intense pressure on German authorities to come up with answers was unlikely to help.
He said officials appear to have jumped the gun again on Sunday by saying bean sprouts were the likely source.
As with an earlier suspicion about Spanish cucumbers, it might have been wiser to wait for data on test results -- although no suspect can be conclusively ruled out yet.
"It's a time for caution and it's also a time for patience," Smith said. "But obviously people are very ill, people are dying and there are diplomatic ramifications, so they''re eager to identify the vehicle of transmission sooner rather than later."
For scientists, success in the sleuthing directly affects their ability to help curb similar outbreaks in the future.
"In the detective work that we do, we like to find the offending organism and the organisms in the patient and then match the two up by DNA fingerprinting," said Wren.
"That can provide a lot of information about how it evolves and give us clues about future outbreaks. So from a microbiologist's point of view it's frustrating when you can't definitively link it to a source."
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