March 26, 2012

Public health 'detectives' tracked clues to illness' cause

By Meredith Goad
Staff Writer

(Continued from page 2)

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Cathy Dragoni, who manages the microbiology department at NorDx, holds control examples of salmonella cultures at the Scarborough laboratories late last month. NorDx offers a variety of testing services for salmonella and other pathogens.

John Ewing/Staff Photographer

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Dr. Stephen Sears, state epidemiologist: "Some people think there’s a case of salmonella today and we know about it tomorrow, and it doesn’t work that way.”

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The USDA has failed to require retailers to track what goes into hamburger meat -- even though better records would protect consumers from some food-borne illnesses.

Most retailers, including Hannaford, do not keep those detailed records and have chosen not to follow federal recommendations to do so.

Federal officials and food safety experts do not believe the salmonella contamination in last year's outbreak happened at Hannaford.

The USDA never found the source of contamination.

The state also assigns its own outbreak team to work on the investigation, Sears said, but "once this becomes a national issue, it really is taken over by the national folks, and we have a lot of conference calls."

Rea became the lead epidemiologist in the investigation, conferencing with the CDC and reporting to Sears and the deputy state epidemiologist.

Officials from the Food Safety and Inspection Service, the public health arm of the USDA, began visiting Hannaford stores, examining its logs for grinder use and talking to store employees.

Michael Norton, director of corporate communications at Hannaford, said the visits provided "some insight that something's going on, but not an epidemiologist saying 'Here's what we think we've got.' "

"They're not saying we've got an outbreak of illnesses associated with ground beef at Hannaford," Norton said.

Then, on Dec. 15, Hannaford officials joined federal and state public health officials on the conference call that declared an outbreak and launched a recall of Hannaford ground beef.

Once investigators know they have an outbreak on their hands, field epidemiologists from the Maine CDC begin contacting patients once again to inform them that they are part of a cluster of illnesses, and that they need to complete a second, more targeted questionnaire -- in this case, one that asks more specific questions about their exposure to ground beef.

Throughout the process of tracing the illnesses to their source, it was never a given that the salmonella originated in ground beef, even after that became the scientists' number one hypothesis. There have been salmonella outbreaks around the country connected to peanut butter, alfalfa sprouts, vegetarian snacks, chili sauce, cantaloupes, fresh produce, white pepper, salami and other foods.

It can take months to figure out the source and test it. But sometimes, investigators get lucky. In this case, they found that two of the sick patients, one in Maine and one in New York, still had ground beef at home. They were told not to throw it out, and not to eat it, though they probably didn't need any convincing on that point.

The meat went to a lab for testing, following a paper chain of custody.

Even when the source of contamination is believed to be in hand, sometimes they can't be sure. If a package of ground beef has been opened, there's always the potential for cross-contamination.

"The food that someone has left may not have been the source, but it may have been contaminated from the source," Sears said. "What it makes you do is be very careful about saying something is truly associated until you have strong statistical evidence, and that's often very challenging to come by."

The salmonella outbreak eventually sickened 20 people in seven states, according to the official tally. There could be more people who fell ill, but didn't feel sick enough to go to a doctor.

Maine health officials have kept watch for new cases, and also took a look in the rearview mirror.

"We went back and looked at all our salmonellas," Sears said. "Did we miss anything?"

On Feb. 1, the CDC issued a statement saying that the outbreak appeared to be over.

Sears said the relatively small number of cases documented during the investigation may suggest that a small number of organisms got into a limited amount of product.

"If you really had a significant amount of organisms, you probably would have seen more cases," he said.

Staff Writer Meredith Goad can be contacted at 791-6332 or at:


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