The Pennsylvania Department of Health is investigating increased reports of Escherichia coli O157:H7 infections in Pennsylvania. This Alert is intended to notify clinicians to have increased awareness of such infections in patients with gastroenteritis, and to request laboratories to perform cultures to assist in the public health investigation.

E. coli O157:H7 and related Shiga toxin-producing E. coli (STEC) can produce severe bloody diarrhea and abdominal cramping, with or without vomiting. The diarrhea can be non-bloody. Fever is usually absent or not prominent. The incubation period can range from 1-7 days post-exposure, but is most often 3-4 days.

The major complication of E. coli O157:H7 infection is hemolytic uremic syndrome (HUS), which is the triad of microangiopathic hemolytic anemia, thrombocytopenia and renal insufficiency. HUS can occur during the acute phase of illness or when the patient appears to be recovering. HUS is more common as a complication of E. coli infection at the extremes of age (in children <10 years of age or the elderly). Because of the intense abdominal cramping, E. coli infections can be confused with appendicitis, ulcerative colitis or bowel necrosis.

Some clinical laboratories do not routinely test for E. coli O157:H7 or other STEC. Therefore, clinicians should specifically request testing for these organisms when submitting a stool specimen so that appropriate tests can be performed and selective culture media used. Questions about appropriate test methods for E. coli O157:H7 and other STEC should be directed to the Pennsylvania Department of Health Bureau of Laboratories. By regulation, all isolates of E. coli O157:H7 and other STEC must be submitted to the state public health laboratory for molecular subtyping (fingerprinting) such as pulsed-field gel electrophoresis and whole genome sequencing.

Most E. coli O157:H7 infections are foodborne, but waterborne outbreaks have also been recognized. E. coli O157:H7 can also be easily transmitted from person-to-person, especially among young children in child care settings and their caregivers. Care should be taken when handling and disposing of soiled items such as diapers. Food workers with STEC infections, and diarrhea of any cause, should be excluded from work and consultation made with local public health authorities.

Suspected cases should be reported to your local health department or to the Pennsylvania Department of Health at 1-877-PA-HEALTH (877-724-3258). Questions can also be directed to the Bureau of Epidemiology at 717-787-3350.