Today Wally Kennedy, a staff writer for the Globe, reported that when two cases of E. coli infection involving children emerged last month near Carthage, and a third case involving a St. Louis child who visited Jasper County occurred at roughly the same time, health officials immediately suspected a common link. That’s because E. coli infections are rare. Three of them happening at the same time signals to communicable-disease investigators that a common source of exposure is likely.
From the article:

“It was very suspicious,” said Tony Moehr, director of the Jasper County Health Department. “We suspected a link early on because the probability of one was great. But, the evidence did not show any link. It’s unusual to have two cases with similar onset dates without there being a link.”
“We looked at the ground meat they consumed and the grocery stores where it was purchased,” Moehr said. “The beef came from different sources. One of the children does not eat beef products, only chicken. We tracked every piece of information we could find about their foods and their activities.”
Investigators also checked beef-recall records. There was a beef recall shortly before the outbreak, but none of the suspect beef was shipped to this area based on shipping records, Moehr said.

The outbreak started in late May and apparently has ended, with no other cases having been reported. One of the children from the Carthage area was the index case for multiple cases that subsequently emerged at a Joplin day-care center. The index child from Carthage and four children at the day-care center developed hemolytic uremic syndrome or kidney failure that required hospitalization. They have since recovered.
The other child from the Carthage area also developed the syndrome, but had no connection to the other child from Carthage and was not enrolled in the Joplin day-care center.
The outbreak affected a dozen or so children in the day-care center. The serious cases in the center were confirmed through lab tests as E. coli.
Each year in the United States, an estimated 73,000 cases of infection and 61 deaths occur because of E. coli, according to the federal Centers for Disease Control and Prevention. Most illnesses are associated with eating undercooked ground beef. Person-to-person contact within families and child-care centers also is a factor.
Pekarek said it is likely that the source of the exposure involved the children’s environment. One of the more prominent possibilities is improperly cooked hamburger.