Escherichia coli O157 Infection and Hemolytic Uremic Syndrome (HUS), 2008

During 2008, 120 culture-confirmed cases of Escherichia coli O157 infection (2.3 per 100,000 population) were reported. The number of reported cases represents a 26% decrease from the median number of cases reported annually from 1997 to 2007 (median, 163 cases; range, 110 to 219) and the number of cases reported in 2007 (n=163). During 2008, 36 (30%) cases occurred in the metropolitan area. One hundred five (88%) cases occurred during May through October. The median age of case-patients was 11 years (range, 2 months to 91 years). Twenty-five percent of case-patients were 4 years of age or younger. Thirty-three (28%) case-patients were hospitalized; the median duration of hospitalization was 5 days (range, 1 to 20 days). None died.

In addition to the 120 culture-confirmed E. coli O157 cases, 69 cases of Shiga-toxin producing E. coli (STEC) infection were identified in 2008. Of those, culture-confirmation was not possible in 8, and therefore it is unknown if those were O157 or another serogroup. Among the remaining 61 cases of STEC other than O157, E. coli O103 accounted for 17 cases, E. coli O111 for 16, and E. coli O26 for 14. These three serogroups represented 77% of all non-O157 STEC.

Six E. coli O157:H7 outbreaks and one E. coli O111:NM outbreak were identified during 2008. Five of the outbreaks involved person-to-person transmission, one involved animal contact, and the mode of transmission was undetermined in one outbreak. All seven outbreaks occurred from May through October.

In May - June, an outbreak of E. coli O157:H7 infections occurred at a childcare center in Murray County. The investigation identified 21 children in four different age groups (infant, toddler, pre-school, and school age) with diarrheal symptoms over the course of the outbreak. Seventeen persons tested positive for E. coli O157:H7 with the same pulsed-field gel electrophoresis (PFGE) subtype, including one teacher, one family member of a child that attended the center, and four persons who reported not having a recent history of gastrointestinal symptoms. Four cases were hospitalized; one developed HUS. Transmission was person-to-person.

In June, an infection control professional from a Brown County hospital reported a hospitalized case of E. coli O157:H7 in a resident of a long-term care facility. Two additional residents of the same wing of the facility also were hospitalized with bloody diarrhea and onset of illness on the same day as the culture-confirmed case. One of those two persons died without being tested for E. coli O157:H7. Among the eight residents of one wing of the facility, five ultimately tested positive for E. coli O157:H7, and two were hospitalized. No cases were identified among the staff, the residents of the other wing of the facility, or in the community. The environmental health evaluation did not reveal any deficiencies in food storage, handling, or preparation. This was a point-source outbreak, but the source was not identified.

Two cases of E. coli O157:H7 infection with the same PFGE subtype from Fillmore and Winona Counties were identified in June. The cases had contact with cattle at a farm where one of the cases worked and the other one visited.

Three E. coli O157:H7 infections with the same PFGE subtype in children, including a case of HUS, were identified in Olmsted County in August. The cases occurred as a result of person-to-person transmission among acquaintance households subsequent to a pool party at the home of a child with diarrhea.

In September, six children became ill with E. coli O157:H7 infections of the same PFGE subtype as a result of person-to-person transmission in a childcare setting in Washington County. Among the remaining nine children that attended the childcare, three children reported gastrointestinal symptoms but tested negative for E. coli O157:H7. None of the children were hospitalized.

Three children that attended a small home childcare and a parent were infected with E. coli O157:H7 due to person-to-person transmission in Stearns County in September and October. None were hospitalized.

Also in September and October, two children who attended a home childcare in Dakota County were infected with E. coli O111:NM. A sibling of another child that attended the home childcare tested positive at a later date. The mode of transmission was person-to-person. None of the children were hospitalized.

Hemolytic Uremic Syndrome (HUS)

In 2008, 11 HUS cases were reported. There were no fatal cases. From 1997 to 2007, the median annual number of reported HUS cases in Minnesota was 18 (range, 10 to 25), and the overall case fatality rate was 6.0%. In 2008, the median age of HUS case-patients was 5 years (range, 2 to 45 years); 9 of the 11 cases occurred in children. All 11 case-patients were hospitalized, with a median hospital stay of 8 days (range, 3 to 20 days). All 11 HUS cases reported in 2008 were post-diarrheal. E. coli O157:H7 was cultured from the stool of five (46%) case-patients, and E. coli O11:H8 was cultured from the stool of one (9%) case-patient. In addition, two (18%) HUS case-patients were positive for E. coli O157:H7 by serology.

• For up to date information see:E. coli O157:H7 and HUS
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2008