To understand what's going on behind the scenes in Germany - where about 16 people have died from E.coli related diseases, you can look at Chapter 2 of Numbers Rule Your World. Here is a decent report by the Wall Street Journal, summarizing what is currently known.
As in the E.coli outbreak investigations done here, the health body in Germany/Europe is hurriedly trying to determine which food product has spread the infections. They had initially suspected Spanish cucumbers. This has proven to be a false positive, as lab tests showed that these cucumbers had on them a different strain of E.coli than the one that killed people.
However, the false positive has temporarily wiped out the Spanish cucumber business. According to the report:
many nations have put partial bans on Spanish vegetables, including tomatoes and cucumbers. This has been a huge hit to Spain, where agriculture makes up about 15% of gross domestic product. The crisis is affecting 70,000 jobs in Spain, Fernando Marcen, head of Spain's Agricultural Cooperatives, said Tuesday.
The statistical challenge in this type of investigations is extremely small sample size, and wide exposure to the potential cause. We are talking about hundreds of cases of infections but millions of people who eat cucumbers, or whatever other food is that might be causing the outbreak. In other words, there are manyfold more people who are exposed to the source but have not fallen ill than those who have fallen ill.
Food for thought: What's missing from the picture in the WSJ report is the lack of government mandated "recalls" of suspected foods. That's a very different attitude than what we have here in the U.S. As I noted in the book, it is frequently true that by the time the investigation turns up a strong suspect leading to a recall, those batches of contaminated foods would have all been eaten or thrown away.