March 26, 2012

Public health 'detectives' tracked clues to illness' cause

By Meredith Goad mgoad@pressherald.com
Staff Writer

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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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KEY FINDINGS

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.

Meanwhile, on the ground, a much more low-tech investigation was going on.

"At the time when we first were investigating the individual cases, we did not know they were connected, especially because they were in four different counties and none of the people were related to each other," said Vicki Rea, a Maine CDC field epidemiologist based out of Bangor.

As soon as a new case of salmonella, or any other reportable disease, is reported to the state, an epidemiologist calls the physician who originally ordered the test to make sure the health care provider has informed the patient about the diagnosis.

"We like for the provider to tell the patient first, before we sort of call out of the blue," Rea said.

The epidemiologist gets the patients' contact information, and someone from the physician's office alerts the patient to expect a call from the state.

"When we call, we just introduce ourselves and basically try to say this is a routine investigation, we're trying to determine where you might have been exposed to this," Rea said.

In all, four local field epidemiologists were on the ground, working these cases.

The epidemiologist asks the patient questions using a five-page questionnaire that covers everything from demographic information and symptoms to exposures to foods, places and circumstances that might have made them sick.

Do you handle food for a living? Have you had contact with a diapered child or adult, or had contact with someone else who appears to have the same illness?

Have you been traveling? Did you eat at any restaurants during the exposure period, and where? What did you eat? Was it undercooked? Have you shopped at grocery stores, farmers markets or roadside stands during the exposure period? Have you had any contact with animals? What's the source of your drinking water?

A lot of people might find it difficult to remember what they had for dinner last night, much less 10 days ago. If the patient can't remember, the investigator may ask if a particular food is something they would generally eat in their diet.

"Some people say for sure they don't eat meat, or they don't eat fish, or that kind of thing," Rea said. "That helps a little bit."

Most of the time the interview is done over the phone, but epidemiologists will go to visit patients in the hospital if they are very ill.

In Maine, two of the salmonella victims were sick enough to be hospitalized.

"Generally speaking, people are hospitalized because they are dehydrated," Sears said. "They often have underlying illness that's made much worse (by the salmonella infection), so if they have heart disease, lung disease, diabetes, cancer, something like that, they're the ones that are most vulnerable to these conditions."

Usually when a salmonella case pops up in Maine, it's an isolated case that can't be linked to any other cases, Sears said. But when PulseNet starts making connections through genetic fingerprints, health officials know they have a potential outbreak on their hands.

"In this case, we found over time four organisms of salmonella that were the same PFGE pattern," Sears said. "They were in different geographic locations, and then those began to match some that were seen in several other states in New England. When that happens, you ask the question 'Is there a common vehicle for this?' Or is there some common contaminant somewhere along the way?"

By early December, the federal CDC epidemiologist looking for genetic fingerprint matches had connected the dots on PulseNet and identified a potential multi-state outbreak of salmonellosis. At this point in an investigation, the CDC dispatches its "OutbreakNet" team to lead the effort to track the disease, and to coordinate communication between public health officials in different states.

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