Identifying Source of Deadly E. Coli Remains a Challenge

When public health officials notice an unusual number of people coming down with food poisoning, the first thing they try to do is to find out what they all ate recently.  E. coli usually takes three or four days to make a person sick, but it may take a week or more. And that presents the first problem.
"Can you tell me what you ate for dinner on May 30?" asks David Weber, professor of epidemiology at the University of North Carolina at Chapel Hill. He says people often do not remember everything they ate over the past week. And even if they do, they may not know all the ingredients, or where they came from. For example, he says, a tomato condiment called salsa was one of the suspects in a 2008 Salmonella outbreak in the United States.