Escherichia coli O157 Infection and Hemolytic Uremic Syndrome (HUS), 2011

During 2011, 146 culture-confirmed cases of Escherichia coli O157 infection (2.8 per 100,000 population) were reported. The number of reported cases is similar to the median number of cases reported annually from 1997 to 2010 (median, 151 cases; range, 110 to 219). During 2011, 68 (47%) cases occurred in the metropolitan area. One hundred nineteen (82%) cases occurred during May through October. The median age of the cases was 19 years (range, 1 to 90 years). Twenty-one percent of the cases were 4 years of age or younger. Sixty (41%) cases were hospitalized; the median duration of hospitalization was 4 days (range, 1 to 61 days). One case died.

In addition to the 146 culture-confirmed E. coli O157 cases, 115 cases of Shigatoxin producing E. coli (STEC) infection were identified in 2011. Of those, culture-confirmation was not possible in 13, and therefore it is unknown if those were O157 or another serogroup. Among the remaining 102 cases of STEC other than O157, E. coli O26 accounted for 24 cases, E. coli O111 for 22, and E. coli O103 for 21. These three serogroups represented 66% of all non-O157 STEC.

In 2011, an outbreak caused in party by non-O157 STEC was identified among individuals who visited an apple orchard in October. In total, 14 cases were identified, including 5 laboratoryconfirmed E. coli O111:NM cases and 3 laboratory-confirmed Cryptosporidium parvum cases. Consuming samples of unpasteurized apple cider from a pressing demonstration was associated with illness. E. coli O111:NM was isolated from a calf at the orchard’s petting zoo.

Six E. coli O157:H7 outbreaks were identified during 2011. Four outbreaks involved foodborne transmission (including two outbreaks with cases in multiple states) one involved animal contact, and one involved person-toperson transmission. The six outbreaks resulted in a median of 3 culture-confirmed cases per outbreak (range, 2 to 8 cases).

An outbreak of E. coli O157:H7 infections associated with animal contact at a county fair occurred in August; both cases reported contact with goats. Two culture-confirmed cases with the same PFGE subtype were identified.

In July, 3 cases of E. coli O157:H7 infection were associated with a private event. Fresh fruit was associated with illness. The fruit was prepared in a household in which household members had recently visited a goat farm from which E. coli O157:H7 was isolated.

In July, 3 cases of E. coli O157:H7 infection were associated with person-to- person transmission in a day care. The index case had contact with goats at a farm from which E. coli O157:H7 with the same PFGE subtype was isolated.

During September - October, 4 cases of E. coli O157:H7 infection in Minnesota residents were part of a multi-state outbreak that resulted in 26 cases in 14 states. Pre-packaged romaine lettuce was implicated as the vehicle.

In October, 2 cases of E. coli O157:H7 infection in Minnesota residents were part of a multi-state outbreak that resulted in 58 cases in 9 states. Romaine lettuce was implicated as the vehicle. This investigation resulted in a recall of the implicated product.

Hemolytic Uremic Syndrome (HUS)

In 2011, 12 HUS cases were reported. The number of reported cases represents a 29% decrease from the median number of cases reported annually from 1997 to 2010 (median 17 cases; range, 10 to 25). In 2011, the median age of HUS cases was 4 years (range, 1 to 88 years); 10 of the 12 cases occurred in children. All 12 cases were hospitalized, with a median hospital stay of 14 days (range, 9 to 61 days). There was 1 fatal case. From 1997 through 2011, the overall case fatality rate was 5.3%. All 12 HUS cases reported in 2011 were post-diarrheal. E. coli O157:H7 was cultured from the stool of 9 (75%) cases; the remaining 3 (25%) HUS cases were positive for E. coli O157:H7 by serology. In 2011, there were no 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, 2011