Foodborne illness on physicians' radar as cases rise

The CDC linked land animal products to the most outbreak-associated hospitalizations and deaths between 1998-2008. Bacterial illnesses were attributed most often to dairy and poultry.

By — Posted Feb. 11, 2013

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This winter, Chicago chronic disease pediatrician Ruby Roy, MD, has seen up to five children a week who are sick with norovirus.

She usually recommends that such patients stay hydrated and rest, the typical instructions physicians give to those with the illness. But Dr. Roy said she doesn't usually give much thought to the possible source of the gastrointestinal illness.

“I don't necessarily go back and think, 'I wonder where this [norovirus infection] came from. Did this come from food?' ” she said.

She now plans to consider such details after a recent Centers for Disease Control and Prevention report showed that norovirus caused a majority of the nation's foodborne disease outbreaks between 1998 and 2008. During the study period, norovirus triggered 1,419 outbreaks and 41,257 outbreak-associated illnesses. In those cases, food is not contaminated where it is grown, but rather is tainted by someone cooking or storing the products, the CDC said. The data were published online Jan. 29 in the CDC journal Emerging Infectious Diseases.

“It's not necessarily our responsibility as individual doctors to investigate” potential foodborne illness outbreaks, said Dr. Roy, who co-directs the Cerebral Palsy Medical Home Pilot Project at La Rabida Children's Hospital in Chicago. “But from my standpoint, I need to think of this more.”

Because primary care doctors often see patients who are sick with foodborne diseases, health experts encourage those physicians to be aware of clusters of illnesses, such as norovirus, and to contact local health departments when they think the incidents could be related.

For the CDC report, researchers for the first time organized the large number of foods implicated in the nation's outbreaks between 1998 and 2008 into 17 commodities. Those commodities fall into three broad categories: aquatic animals, which include fish and mollusks; land animals, including beef, dairy, eggs and poultry; and plants, which include fruits-nuts, grains-beans and leafy vegetables.

The CDC took on the task of estimating the food sources of all foodborne illness that occurred during the study period after publishing a 2011 report showing that about one in six Americans contracts foodborne illness in a year and that an estimated 3,000 die.

“As soon as we published [those estimates,] the next question was: Which foods make us ill?” said Robert V. Tauxe, MD, MPH, co-author of the latest CDC report. He also is deputy director of the agency's division of foodborne, waterborne and environmental diseases.

The new findings are a reminder about the prevalence of foodborne illness, said William Schaffner, MD, chair of the Dept. of Preventive Medicine at Vanderbilt University School of Medicine in Nashville, Tenn.

“Whenever we get these reports from the CDC, we're reminded that although we do have the safest food supply in the world, it's not completely safe,” he added.

Top culprit behind foodborne illness

Leafy vegetables top the list of food products that made people sick during a 10-year period.

During the study period, 13,352 foodborne disease outbreaks causing 271,974 illnesses were reported in the U.S., the CDC reported. But not all of the incidents had implicated food sources.

For the latest CDC study, researchers examined data from 4,589 outbreaks, each of which had an implicated food source and a single infectious agent. Topping the list of foods that made people sick were leafy vegetables. They were associated with 2.1 million, or 23%, of outbreak-related illnesses during the study period, more than any of the other commodities that were examined, the CDC said.

Contributing to the potential health risks of this food type is that it's grown above the soil, where it could be exposed to bacteria through contaminated water or animals that defecate nearby, said microbiologist Angela Shaw, PhD. “This is not an easily controlled environment,” said Shaw, assistant professor of food safety in the Dept. of Food Science and Human Nutrition at Iowa State University.

The Food and Drug Administration has recommended two new food safety rules pertaining to produce that are aimed at preventing foodborne illness. The proposals, which include requiring farms that grow or harvest produce to follow enforceable standards aimed at preventing contamination of the products, stem from the FDA Food Safety Modernization Act, which President Obama signed into law on Jan. 4, 2011.

Land animal commodities were linked to a plurality of annual outbreak-associated hospitalizations (46%) and deaths (43%), the report said. Within that food category, poultry was associated with the most deaths (19%), the CDC said. Many of those fatalities were caused by Listeria or Salmonella, the agency said.

Bacterial illnesses were attributed most often to dairy and poultry (18%), the CDC said. Much of the dairy-related illness was due to the increasingly common practice of consuming unpasteurized milk, Dr. Tauxe said. Drinking raw milk is a consumer trend the CDC is concerned about, he said. “The practice of pasteurizing milk is one of the greatest public health achievements of the 20th century.”

Dr. Tauxe acknowledged that most foods implicated in foodborne illness outbreaks are healthy products that doctors recommend patients eat more frequently. However, he said, “The findings don't mean people should stop eating one or another category of food.” He encouraged doctors to continue urging people to consume fresh produce and poultry.

Alert physicians are key

When Dr. Roy discusses nutrition with her patients' families, she plans to add a few sentences about food safety, including the need to rinse produce before eating it. She also intends to encourage patients to cook vegetables rather than always putting them into a salad, because the heat will kill much of the bacteria on the produce.

Shaw recommends that doctors sign up on the Food and Drug Administration's website to receive daily emails on food recalls.

“It gives you the latest information on what to be concerned with,” Shaw said. She encourages physicians to pass on this information to patients when relevant.

Doctors also play an important role in identifying foodborne disease outbreaks, because ill patients often come to them for care, Dr. Schaffner said. He recommends that physicians be alert to outbreaks and contact local health departments if they think such incidents are occurring in their communities.

Federal officials don't intend to burden physicians with investigating and identifying outbreaks, Dr. Schaffner said. “But so much of what we are able to do in public health depends on alert primary care physicians who look up and say, 'Wait a minute. This may be a problem beyond this single problem in front of me.' ”

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External links

“Attribution of Foodborne Illnesses, Hospitalizations, and Deaths to Food Commodities by using Outbreak Data, United States, 1998–2008,” Emerging Infectious Diseases, Centers for Disease Control and Prevention, published online Jan. 25, (link)

Food and Drug Administration on food recalls, market withdrawals and safety alerts (link)

Centers for Disease Control and Prevention on food safety and foodborne illness (link)

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