Incidence
of foodborne illnesses increases with arrival of warm weatherMay 1997
ATLANTA — Picnics, baseball games and days at the shore are all associated with warm and sunny summer days, but so are foodborne gastrointestinal illnesses, according to Larry Slutsker, MD.
Epidemiological data reveal the incidence of foodborne GI illness increases in the late spring. This could easily be attributed to rising temperatures which cause bacteria to multiply, and to the desire to eat outside where food may be warmed by the sun, said Slutsker, a medical epidemiologist with the Centers for Disease Control and Prevention (CDC).
Foodborne infection is responsible for an estimated 6.5 million to 33 million cases of human illness and 9,000 deaths each year in the United States, according to the CDC. The figures, however, are only estimates because not everyone with a foodborne illness sees a doctor, and physicians do not always obtain stool cultures, he said.
The seven foodborne diseases reported for 1996 included: Campylobacter, Escherichia coli O157:H7, Listeria, Salmonella, Shigella, Vibrio, and Yersinia. Isolation patterns varied by season for several pathogens, but some were more prevalent during the summer months: 50% of E. coli O157:H7, 35% of Campylobacter and 33% of Salmonella, according to the CDC.
Distinguishing bacterial foodborne GI illness from sporadic viral illness not spread by food is sometimes a challenge. Patients with prolonged illness, particularly if the illness is associated with bloody diarrhea, is a good sign of bacterial foodborne infection, as well as a patient who was among others who became sick after eating food at a particular place or event, said Slutsker, of the CDC Foodborne and Diarrheal Diseases Branch.
The most common of the seven bacterial pathogens to cause foodborne illnesses are Campylobacter, Salmonella, and E. coli O157:H7.
Campylobacter is the most common foodborne illness in the United States, and erythromycin is the treatment of choice, Slutsker said.
Treatment for the infection usually is recommended for very young or very old patients and for patients experiencing severe illness, as indicated by bloody diarrhea and high fever. Treatment is also encouraged for patients with symptoms which have not improved or have worsened since the diagnosis, and for patients with persisting symptoms lasting more than a week.
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Fever, abdominal pain and diarrhea beginning 12 to 72 hours after eating contaminated food are classic symptoms of Salmonella. Illness usually lasts four to seven days, and most people recover without antibiotic treatment. Treatment is generally reserved for the elderly, infants, the immunosuppressed and any others at high risk for severe complications.
E. coli O157:H7 must be considered when children present with bloody diarrhea with severe abdominal cramps. Another classic symptom is abdominal tenderness, which occurs more frequently with E. coli O157:H7 than with other foodborne diseases.
Slutsker said pediatricians should specifically request laboratories to test for E. coli O157:H7 because it is sometimes confused with appendicitis, and not all laboratories test for the pathogen.
Antibiotic treatment has not proven effective, and most patients recover on their own within five to 10 days. Hemolytic uremic syndrome (HUS) develops in about 10% of children under age 10 who have E. coli O157:H7, according to Phillip I. Tarr, MD, a pediatric gastroenterologist with Children's Hospital and Medical Center, Seattle.
Antibiotics for preventing E. coli related HUS are not recommended, because in retrospective analyses, patient who received antibiotics had the same or greater risk for developing HUS than those who receive no antibiotics, Tarr said.
Although undercooked ground beef is most commonly associated with E. coli O157:H7, new vehicles such as apple cider, lettuce and salami have been implicated.
Tarr stressed the importance of rapidly report cases to public health authorities because children with E. coli O157:H7 infection could be part of an unrecognized continuing outbreak from a widely disseminated vehicle.
Based on surveillance data on culture-confirmed cases of the seven foodborne diseases for 1996, incidence rates were highest for campylobacteriosis (25:100,000 population), followed by salmonellosis, shigellosis, E. coli O157:H7, Yersinia, listeriosis and vibriosis, according to a recent Morbidity and Mortality Weekly Report. A total of 7,223 culture-confirmed cases of the seven foodborne diseases were identified from stool specimens or specimens from normally sterile sites.
For all diseases except salmonellosis, rates varied substantially among the testing sites.
Rates also varied by age. Among children younger than 1 year, the rate for salmonellosis ranged from 73 to 270:100,000. The rates ranged from 25 to 193:100,000 for campylobacteriosis.
The information was gathered by the Foodborne Diseases Active Surveillance Network (FoodNet). The program was developed by the CDC in 1994 to determine more precisely the burden of foodborne disease in the United States; to determine the proportion of specific foodborne diseases associated with certain contaminated foods or with other exposures; and to provide the framework to respond rapidly and collaboratively to emerging foodborne diseases.
For more information:
- CDC. Foodborne diseases active surveillance network, 1996. MMWR 1997; 46:258-261.
- Charnow J. Be alert for foodborne illnesses. Infectious Diseases in Children 1996;5:14.
- Richards C. Children with E. coli 0157:H7 should be monitored for HUS. Infections Diseases in Children 1996;12:16.
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