Escherichia coli O157 Infection and Hemolytic Uremic Syndrome (HUS), 2006

During 2006, 147 culture-confirmed cases of Escherichia coli O157 infection (2.8 per 100,000) were reported. Although the number of reported cases represents a 16% decrease from the median number of cases reported annually from 1997 to 2005 (median, 175 cases; range, 110 to 219), it represents a 21% increase from the 121 cases reported in 2005 and the highest count since 2003. Seventy-one (48%) cases occurred in the metropolitan area. Eighty (54%) cases occurred during July through September. The median age of case-patients was 17 years (range, 7 months to 88 years). Sixty-one (41%) case-patients were hospitalized; the median duration of hospitalization was 4 days (range, 1 to 39 days).

Three E. coli O157 outbreaks were identified during 2006; all were food-borne. One outbreak occurred in July, resulting in 17 cases, four of which were culture-confirmed. Nine of the cases were hospitalized, three developed hemolytic uremic syndrome (HUS), and one died. The likely source of this outbreak was ready-to-eat foods served at a church smorgasbord that likely had been contaminated by ground beef used simultaneously to prepare meatballs for the event. Some of the cases likely were associated with restaurants that purchased ground beef from the same grocery store that supplied the church. E. coli O157:H7 of the rare outbreak PFGE subtype was isolated from beef trimmings from a USDA-inspected plant in the weeks prior to the outbreak, suggesting that the beef was likely already contaminated when received by the store. A second outbreak was identified in August, resulting in three cases, including one case that developed HUS. No deaths occurred. All three cases ate at the same restaurant in the week before their illness. No specific food vehicle was identified, but shredded iceberg lettuce was the only common menu item consumed by all the cases. The third outbreak was associated with shredded iceberg lettuce consumed at restaurants from a fast-food Mexican chain in Minnesota and Iowa in December. This outbreak resulted in 32 cases, including 12 that were culture-confirmed. Eight case-patients were hospitalized and one developed HUS. No deaths occurred. The outbreak strain of E. coli O157:H7 was recovered from environmental samples collected from dairy farms near the source fields for the contaminated lettuce in California.

In 2006, 19 HUS cases were reported. There was one fatal case, aged 73 years. From 1997 to 2006, the median annual number of reported HUS cases in Minnesota was 16 (range, 9 to 25), and the overall case fatality rate was 7.4%. In 2006, the median age of HUS case-patients was 5 years (range, 1 to 73 years); 13 of the 19 cases occurred in children. All 19 case-patients were hospitalized, with a median hospital stay of 11 days (range, 3 to 39 days). Eighteen of the 19 HUS cases reported in 2006 were post-diarrheal; one HUS case followed a Streptococcus pneumoniae infection. E. coli O157:H7 was cultured from the stool of 14 (74%) case-patients. E. coli O157 serology was positive in one HUS patient with a negative stool culture. E. coli O145:NM was isolated from one case-patient.

• 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, 2006