Escherichia coli O157 Infection and Hemolytic Uremic Syndrome (HUS), 2010

During 2010, 140 culture-confirmed cases of Escherichia coli O157 infection (2.7 per 100,000 population) were reported. The number of reported cases represents a 13% decrease from the median number of cases reported annually from 1997 to 2009 (median, 160 cases; range, 110 to 219) (Figure 2). During 2010, 67 (48%) cases occurred in the metropolitan area. One hundred twenty (86%) cases occurred during May through October. The median age of the cases was 15 years (range, 4 months to 80 years). Twenty-five percent of the cases were 4 years of age or younger. Fifty-three (38%) cases were hospitalized; the median duration of hospitalization was 3 days (range, 1 to 81 days). One case died.

In addition to the 140 culture-confirmed E. coli O157 cases, 117 cases of Shiga-toxin producing E. coli (STEC) infection were identified in 2010. Of those, culture-confirmation was not possible in 12, and therefore it is unknown if those were O157 or another serogroup. Among the remaining 105 cases of STEC other than O157, E. coli O26 accounted for 23 cases, E. coli O111 for 23, and E. coli O103 for 18. These three serogroups represented 61% of all non-O157 STEC.

In 2010, one outbreak of non-O157 STEC was identified among students in a high school class. In total, 29 cases were identified, including 6 laboratory-confirmed cases. Venison provided by students, and butchered and cooked on school grounds, was identified as the vehicle. E. coli O103:H2 and E. coli O145:NM were both isolated from ill students and leftover venison. This is the first documented non-O157 STEC outbreak associated with venison.

Six E. coli O157:H7 outbreaks were identified during 2010. Four outbreaks involved foodborne transmission, including two outbreaks with cases in multiple states, one involved waterborne transmission, and one involved person-to-person transmission. The six outbreaks resulted in a median of 4 culture-confirmed cases per outbreak (range, 2 to 9 cases).

An outbreak of E. coli O157:H7 infection associated with the consumption of raw milk from one farm occurred from May to June. Eight culture-confirmed cases with the same PFGE subtype were identified. One case developed HUS.

In July, 9 cases of E. coli O157:H7 infection with the same PFGE subtype occurred in Minnesota residents. The outbreak was most likely caused by an imported snack; however, the vehicle was not confirmed. One case developed HUS.

In July, 5 cases of E. coli O157:H7 infection were associated with swimming at a specific beach. The investigation resulted in the closure of the beach until water testing results became available. One case developed HUS.

In August, an outbreak of E. coli O157:H7 infection associated with person-to-person transmission occurred at a daycare in Stearns County. Two culture-confirmed cases were identified, and both cases developed HUS.

In October, 2 cases of E. coli O157:H7 infection in Minnesota residents were part of a multi-state outbreak that resulted in 8 cases in four states. Unpasteurized artisanal cheese was implicated as the vehicle. This investigation resulted in a recall of the implicated product.

From December 2010 through January 2011, 3 cases of E. coli O157:H7 infection with the same PFGE subtype occurred in Minnesota residents. One of these three cases occurred in December. These cases were part of a multi-state outbreak that resulted in 8 cases in three states. In-shell hazelnuts were confirmed as the vehicle, and the implicated product was recalled. This was the first documented E. coli O157:H7 associated with hazelnuts. Contamination likely occurred in the orchard as hazelnuts were collected from the ground.

Hemolytic Uremic Syndrome (HUS)

In 2010, 17 HUS cases were reported. There were no fatal cases. The number of reported cases represents a 6% increase from the median number of cases reported annually from 1997 to 2009 (median 16; range, 10 to 25). From 1997 through 2010, the overall case fatality rate was 5.2%. In 2010, the median age of HUS cases was 3 years (range, 1 to 62 years); 13 of the 17 cases occurred in children. All 17 cases were hospitalized, with a median hospital stay of 12 days (range, 4 to 57 days). All 17 HUS cases reported in 2010 were post-diarrheal. E. coli O157:H7 was cultured from the stool of 14 (82%) cases; 1 (6%) additional HUS case was positive for E. coli O157:H7 by serology. Enterotoxigenic E. coli (ETEC) was identified in the stool of 1 (6%) case. However, ETEC is not a known cause of HUS. In 2010, there were 5 outbreak-associated HUS cases.

• 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, 2010