By the time most of Michigan learned of the 42-state salmonella outbreak declared last week, the worst of the spike was over.
About 400 people -- 20 in Michigan -- fell ill between Sept. 3 and Dec. 29 after eating food contaminated with the insidious bacteria. Seven Michiganders have landed in the hospital. One death in Minnesota may be linked to the outbreak.
By now, as federal and state health officials track down the offending food source, almost all those people are back to normal, as are the hundreds more who health officials say likely fell ill with salmonella that was never confirmed by laboratory tests.
Declaring a salmonella outbreak months after the first infections are reported may seem to have little value, but it illustrates the deliberate process needed to determine whether there is cause for concern. And it often serves as a warning that another wave could be on the way -- and that infections are largely preventable.
"This is a long, slow process, unfortunately," said Dr. Melinda Wilkins, communicable disease director for the Michigan Department of Community Health.
Declaring an outbreak is subject to a chain of events dependent on individual actions that take anywhere from hours to weeks. On top of that is finding peaks and patterns in laboratory-confirmed salmonella cases above the 800 to 900 sporadic confirmed infections that happen in Michigan each year.
"It takes two to three weeks minimum to know if it's part of an outbreak, based on molecular work," she said, referring to the DNA tests that allow public health officials to link salmonella infections in Michigan with salmonella infections in Texas, for instance. But the detective work has started long before then, she said.
It starts with the onset of symptoms -- nausea, vomiting, intestinal cramping and diarrhea -- severe enough to lead a person to go to a hospital, where a doctor might call for a salmonella test.
It can then take up to two weeks from the time a stool sample is collected until a series of tests can identify and link salmonella in different parts of the country.
"It's historical information, trying to remember what they did a week ago," said Dr. Herbert Smitherman, assistant dean of community and urban health at the Wayne State University School of Medicine. "It just takes a while to compile the data."
Weeks can pass before the U.S. Centers for Disease Control and Prevention gets involved, interviewing patients and raiding their refrigerators, freezers and cupboards for items that might harbor salmonella.
The current salmonella culprit is Typhimurium, which is brutal to the human digestive tract.
It was the third salmonella outbreak of 2008. The first was traced to Honduran cantaloupes and the second, which affected nearly 1,500 people, was first traced to tomatoes, then to jalapenos. The mistake was costly.
"It just destroyed the tomato industry," said Smitherman.
The investigation continues into the current outbreak and an announcement regarding further infections and possibly a source is expected this week. Minnesota health officials announced Friday that they suspect peanut butter is involved.
Wilkins said she couldn't discuss details of what she called a "fairly slow moving outbreak," but said the culprit was likely something widely distributed and with a long shelf life.
Contact MEGHA SATYANARAYANA at 313-223-4544 or megha@freepress.com. To see more of the Detroit Free Press, or to subscribe to the newspaper, go to http://www.freep.com Copyright (c) 2009, Detroit Free Press Distributed by McClatchy-Tribune Information Services. For reprints, email tmsreprints@permissionsgroup.com, call 800-374-7985 or 847-635-6550, send a fax to 847-635-6968, or write to The Permissions Group Inc., 1247 Milwaukee Ave., Suite 303, Glenview, IL 60025, USA.
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