Suspecting Foodborne Illnesses in Special Populations: Quick Facts for Providers

Christopher R. Braden, MD


December 17, 2012

Editorial Collaboration

Medscape &

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Hello. My name is Dr. Christopher Braden, medical epidemiologist and infectious disease specialist at the Centers for Disease Control and Prevention (CDC).

Thank you for watching this CDC Expert Video Commentary on Medscape.

Foodborne illness is common and can happen to anyone. CDC estimates that each year, roughly 1 out of 6 Americans (48 million people) become sick, 128,000 are hospitalized, and 3000 die of foodborne diseases.[1] But did you know that some people have a much higher risk for foodborne infection?

It is estimated that 20% of the US population has underlying conditions that put them at a greater risk of contracting a foodborne disease. The risk for infection varies at different ages and stages of health. Infections can be more severe, resulting in long-term health consequences or death.

Today I would like to share 3 facts about foodborne illness to help you recognize and diagnose those at greatest risk:

Fact 1. Pathogens that contaminate food can cause sickness, long-lasting health problems, or death in some groups. Young children, pregnant women and their newborns, patients undergoing transplants, and those who are immunosuppressed have an increased risk for infection associated with certain foodborne pathogens (Table 1)

Table 1. Pathogens Affecting Key High-Risk Populations[1]

High-Risk Populations Foodborne Pathogens
People with primary immunodeficiencies Giardia, Campylobacter, Salmonella
Transplant recipients Listeria monocytogenes, Cryptosporidium, Giardia, Salmonella, and others
People with diseases of the immune system Varies by disease
HIV Salmonella, Giardia
AIDS Listeria
Pregnant women Listeria monocytogenes, Toxoplasma gondii
Neonates, young infants Clostridium botulinum, Cronobacter, Salmonella, and Yersinia enterocolitica
Older adults (>60 years) Listeria, Campylobacter, Salmonella, Escherichia coli O157
People with chronic liver disease Vibrio


  • Young children. Recent data show that foodborne illness resulting from bacteria, such as Salmonella and E coli O157, occur more frequently in children under 5 than in any other age group.[2] Because young children have immature immune systems, infection can occur at lower levels of exposure to foodborne pathogens.[1]

  • Pregnant women and their newborns. The hormonal changes associated with pregnancy also make an expectant mother and her newborn more susceptible to foodborne pathogens like Listeria and Toxoplasma gondii.[3] In the United States, congenital toxoplasmosis occurs in 400-4000 newborns each year, and pregnant women are about 13 times more likely than the general population to acquire listeriosis.[4,5] Whereas a pregnant mother with infection may not become seriously ill, her fetus or newborn often does. Listeriosis can result in premature labor, neonatal sepsis, or meningitis.[6,7] Toxoplasmosis can result in mental disability, vision loss, or seizures. Both can cause miscarriage or death.[4,5]

  • Older adults. Adults 60 years of age or older are at greater risk for hospitalization and death from many foodborne illnesses, such as Salmonella and E coli O157. Moreover, listeriosis occurs more frequently in people age 65 or older than in any other age group.[8]

  • Pre-existing chronic conditions and the side effects of some medications can weaken the immune system, causing higher susceptibility to foodborne pathogens.[9]

  • Patients undergoing transplants. Although foodborne illness is rare in transplant patients, infection from a foodborne disease can cause severe illness in this population. In transplant patients, 20%-30% of Salmonella infections lead to bacteremia.[1]

  • People with other immunocompromising conditions. Those with primary immunodeficiencies, cancer, or other immune system diseases, such as AIDS, and people taking immunosuppressive drugs are at increased risk for many types of foodborne illness. People with chronic liver disease are 80 times more likely to develop Vibrio vulnificus infections than those without liver disease.[10]

Fact 2. Signs and symptoms can differ among diseases. Recognizing what to look for can guide providers to the most suitable treatment for high-risk patients.

  • Patients with foodborne illnesses typically present with gastrointestinal tract symptoms.

  • Key signs and symptoms can occur alone or in combination and include:

    • Bloody diarrhea;

    • Prolonged diarrhea (3 or more unformed stools daily and persisting for several days);

    • Diarrhea leading to dehydration;

    • Abdominal cramps;

    • Fever and chills; and/or

    • Sudden onset of nausea and vomiting.[11]

  • Stool culture is often the most appropriate test for diagnosis. Testing for specific pathogens, including E coli O157 and Vibrio, must be requested because they are not typically included on the routine test panel for enteric pathogens. Preferred specimens for specific foodborne infections for diagnosis in high-risk populations are shown in Table 2.

  • Although many signs and symptoms are gastrointestinal, neurologic involvement (paresthesias, motor weakness, or cranial nerve paralysis) can also result from foodborne intoxications such as botulism or shellfish poisoning.[11]

Table 2. Preferred Specimens for Foodborne Infections in High-Risk Populations

Pathogen Preferred Specimen
Campylobacter Stool sample
Clostridium botulinum Serum, stool, or food, or by culturing C botulinum from stool, a wound, or food
Cronobacter Blood or other samples
Cryptosporidium Stool sample
E coli Stool sample
Giardia Stool sample
Listeria Blood, cerebrospinal fluid (CSF) (if nervous system involvement), or amniotic fluid/placenta (if congenital)
Salmonella Stool sample
Shigella Stool sample
Toxoplasma Blood sample or other body fluids such as CSF, or amniotic fluid (if congenital)
Vibrio Stool sample, wound, or blood sample
Yersinia enterocolitica Stool sample


Fact 3. Astute providers can diagnose infections quickly and alert public health to potential outbreaks.

  • Recognizing foodborne illness can be challenging. Because these symptoms can indicate a variety of illnesses, clinicians should have a high index of suspicion and a low threshold for ordering diagnostic tests, especially when dealing with high-risk patients.

  • Salmonella, Shigella, E coli O157, other Shiga toxin-producing E coli, hemolytic uremic syndrome, and hepatitis A are among the many foodborne infections that are generally reportable everywhere in the United States.[12]

  • Healthcare providers are often the key to identifying outbreaks and mitigating further spread in the community.

  • It is important to recognize when multiple patients exhibit similar signs and symptoms and then communicate suspicions to public health officials.

Two final thoughts that I would like to leave you with are:

  • Be aware. Consider key signs and symptoms of foodborne illness in making the most appropriate diagnosis for high-risk patients; and

  • Be an advocate: Recognize patterns among patients and communicate suspicions of an outbreak to your local or state health department.

More detailed discussions about foodborne illness and prevention strategies for each of these high-risk groups will be presented in other CDC Expert Commentaries on Medscape.

Christopher R. Braden, MD, is a medical epidemiologist and currently serves as the Director of the Division of Foodborne, Waterborne, and Environmental Diseases at the Centers for Diseases Control and Prevention. Previously, Dr. Braden served as the Associate Director for Science in the Division of Parasitic Diseases and as Chief of Outbreak Response and Surveillance within the Enteric Diseases Epidemiology Branch in the Division of Foodborne, Bacterial, and Mycotic Diseases. He also served as a medical epidemiologist in the Division of Tuberculosis Elimination. Dr. Braden earned his BS at Cornell University and MD at the University of New Mexico School of Medicine. He completed his internship and residency in internal medicine and then completed his fellowship in infectious diseases at Tufts Medical Center in Boston, Massachusetts. Afterwards, he became an Epidemic Intelligence Service (EIS) Officer at CDC in 1993. He is a commissioned officer in the U.S. Public Health Service, a member of the American Society for Microbiology, and an associate editor for the Emerging Infectious Diseases journal. He has authored over 60 peer-reviewed publications and textbook chapters. His major areas of interest include molecular epidemiology of infectious diseases, infectious diseases surveillance and outbreak investigation, and national programs in food safety.