Escherichia coli O157:H7

Human stomachs are naturally full of E. coli bacteria. That's something that gets lost in most news reports about the current outbreak.

A majority of the infections have occurred in Wisconsin, where 29 people so far have contracted the disease. Utah had 11 cases, and New York and Ohio each had seven, Acheson said.

Other states where the infection has occurred are California, Connecticut, Idaho, Indiana, Kentucky, Maine, Michigan, Minnesota, New Mexico, Nevada, Oregon, Pennsylvania, Tennessee, Virginia, Washington and Wyoming, Acheson said.

The outbreak is part of a problem in the U.S. food supply that affects about 100,000 to 150,000 people each year. The bacteria can be spread by insufficiently cooked meat, sprouts, lettuce, unpasteurized milk and juice or contact with sewage-contaminated water. The last outbreak involving spinach was in California in 2003.

The bacteria can cause low-grade fever, vomiting and diarrhea, often with bloody stool, the FDA said. Most healthy adults recover within a week, though some people develop serious kidney damage.

The subspecific strain that is now causing problems is O157:H7, the same one that affected thousands of schoolchildren in Japan ten years ago.

To determine the cause of a July 1996 outbreak of Escherichia coli O157:H7 among factory workers in Kyoto, Japan, we conducted cohort and case-control studies. Eating radish sprout salad during lunch at the factory cafeteria had been linked to illness. The sprouts were traced to four growers in Japan; one had been associated with an outbreak of E. coli O157:H7 among 6,000 schoolchildren in Sakai earlier in July.

UPDATE: See the story behind the killer spinach on Carl Zimmer's science blog The Loom.