CDC Expert Commentary

Foodborne Illness: A Handy Overview

Barbara Mahon, MD, MPH


January 24, 2011

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Hello, my name is Barbara Mahon. I'm a pediatrician and infectious disease epidemiologist at CDC, and I'm happy to speak with you today as part of the CDC Expert Video Commentary Series on Medscape. Practicing clinicians know that foodborne disease is a common reason for people to seek medical care. CDC recently published new estimates showing just how big a problem foodborne disease really is. We estimate that almost 48 million illnesses, more than 125,000 hospitalizations, and more than 3000 deaths occur every year because of contaminated food consumed in the United States. That's a lot of illness.

Many different agents -- bacteria, viruses, parasites, chemicals, and toxins can contaminate food. These agents can cause many different clinical syndromes, from fever and bloody diarrhea with Salmonella or Shigella infection, to vomiting and watery diarrhea with norovirus infection, to sepsis or meningitis with Listeria infection -- to name just a few. Gastroenteritis symptoms are the most common presenting complaints in these illnesses, but systemic complications range from hemolytic uremic syndrome (HUS) with Shiga toxin-producing E. coli infection to Guillain Barré syndrome with Campylobacter infection to encephalitis with toxoplasmosis -- again, to name just a few.

The leading causes of foodborne illness are norovirus, Salmonella, Campylobacter, and Clostridium perfringens. Norovirus, Salmonella, and Campylobacter are also among the leading causes of death due to foodborne illness. Two other pathogens, Toxoplasma and E. coli O157, are among the top causes of death. Infections with these pathogens are relatively rare, but they commonly lead to severe complications.

CDC developed these estimates in large part to help policymakers direct resources to the areas where they will do the most good. The food regulatory agencies -- the US Food and Drug Administration and the US Department of Agriculture at the federal level -- as well as consumer groups and the food industry, need this information for their work on improving food safety.

For clinicians, the huge burden of foodborne disease is a reminder to counsel our patients about things they can do to help protect themselves. When you get right down to it, most foodborne diseases are caused by feces getting into food. Contamination can come either from animals -- which are the usual source of Salmonella, Campylobacter, E. coli O157, and many other pathogens -- or from humans, who are the usual source of norovirus.

Because it's relatively easy for feces to be on or in raw or undercooked foods of animal origin, these foods -- like eggs, poultry, meat, or fish -- are common sources of foodborne illness. Raw milk is a particularly hazardous food of animal origin, yet there seems to be a resurgence of interest in drinking it. We should warn our patients against it. Produce should be washed thoroughly and cross-contamination of foods should be avoided. Handwashing is such an important practice -- not only for preventing foodborne disease -- and it's worth reminding patients that they should wash their hands before handling food and, of course, after using the bathroom. And for infants, breastfeeding is probably the single most important practice to protect against foodborne disease.

There is a lot that could be said about diagnostic testing for all the agents that can be transmitted in food, but I want to mention just 1 issue that is particularly important and current, and that is diagnostic testing for Shiga toxin-producing E. coli (STEC), the bad actors that cause HUS. CDC recently published guidelines for clinical laboratories that recommend promptly and simultaneously testing for both the presence of Shiga toxin and for the presence of E. coli O157 in stools from all patients with community-acquired diarrhea or suspected HUS. This strategy will lead to the fastest and most complete identification of these pathogens. So it's important to find out what your lab is doing, and, if necessary, to request testing, if it's not done routinely.

Finally, remember that many infections that are transmitted commonly through food, including salmonellosis, campylobacteriosis, listeriosis, and Shiga toxin-producing E. coli infection, as well as others, are reportable; if you diagnose one of these infections, you should report it to your local health department. Outbreaks can only be detected and investigated if illnesses are reported.

We at CDC hope that this brief overview of foodborne illness has been helpful. For more information, visit the Web resources listed on this page. Thank you for watching.

Web Resources

Estimates of Foodborne Illness in the United States

Shiga Toxin-Producing Escherichia Coli Infections: What Clinicians Need to Know

Barbara Mahon, MD, MPH. Dr Mahon received her MD and clinical training in pediatrics from the University of California, San Francisco and her MPH from the University of California, Berkeley. She trained in CDC's Epidemic Intelligence Service (EIS). Dr. Mahon leads the FoodNet and Outbreak Surveillance Team in the Enteric Diseases Epidemiology and Surveillance Branch at the Centers for Disease Control and Prevention. The team is responsible for the FoodNet active foodborne disease surveillance system and for national surveillance for outbreaks of foodborne disease. It conducts epidemiologic studies of the burden, trends, and food source attribution of foodborne diseases caused by Salmonella, Listeria, and E. coli O157, among other pathogens. Dr. Mahon has a broad background in infectious disease epidemiology, having worked on foodborne diseases, vaccine-preventable diseases, and sexually transmitted diseases in academic and industry positions as well as in government. She also holds an adjunct faculty appointment at the Boston University School of Public Health.


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