“It’s the bean sprouts,” said Reinhard Burger, head of the Robert Koch Institute (RKI), the German federal agency for disease surveillance in Berlin. The verdict, delivered earlier today, finally settles weeks of speculation about the source of the Escherichia coli outbreak which has swept across Europe over the past month (see ‘Microbe outbreak panics Europe’).

The European Centre for Disease Prevention and Control reports that as of today, the rare O104:H4 strain of enterohaemorrhagic E. coli (EHEC) has infected more than 3,000 people in 13 countries across Europe, killing 31. Of those cases, 795 include a complication called haemolytic uraemic syndrome (HUS), triggered by the Shiga toxin produced in the bacteria, which can cause kidney failure, neurological problems and death.

The bacteria were first thought to come from contaminated Spanish cucumbers – later proved to be false. Spain was furious, and there was talk of legal action to compensate farmers for lost sales until the German government agreed to help promote imported Spanish produce (Deutsche Welle).

As The Daily Telegraph notes:

During angry exchanges in the European Parliament, Francisco Sosa Wagner, a Spanish MEP, brandished a cucumber at Mr Dalli and demanded that the EU restore consumer confidence in salad vegetables. "We need to restore the honour of the cucumber,” he said.

On 5 June, authorities then blamed beansprouts grown on an organic farm in northern Germany – but changed their tune after a series of tests on the sprouts were negative.(The Guardian)

Now, investigators have linked people who have fallen ill with 26 restaurants which received produce from the farm. According to an Associated Press report, Andreas Hensel, the head of the country’s risk assessment agency, said: “They even studied the menus, the ingredients, looked at bills and took pictures of the different meals, which they then showed to those who had fallen ill.”

German authorities have been criticised for their handling of the outbreak, so nailing the culprit is a significant step. However, new cases continue to crop up, and there are growing calls for broader reform of Germany’s infection reporting system.

Questions are also being raised about why Shiga-toxin-producing bacteria have become far more common over the past few decades – with some scientists suggesting to Nature that agricultural use of antibiotics may be a factor.

Image courtesy of FotoosVanRobin via Flickr under Creative Commons.