Escherichia coli O157 Infection and Hemolytic Uremic Syndrome (HUS), 2001
During 2001, 219 culture-confirmed cases of Escherichia coli O157 infection (4.5 per 100,000 population) were reported. Ninety-eight (45%) cases occurred in the seven-county Twin Cities metropolitan area. The largest numbers of cases in greater Minnesota occurred in Stearns, Olmsted, Wright, and Douglas counties (13, 12, 11, and eight cases, respectively). One hundred sixty-six (76%) cases occurred during June through October. The median age of E. coli O157 case-patients was 13 years (range, 1 month to 87 years), and 123 (56%) were female. Eighty-one (37%) cases were hospitalized for a median of 3 days (range, 1 to 21 days).
Six outbreaks of E. coli O157:H7 were identified in 2001. One large outbreak involving 27 culture-confirmed cases and two smaller outbreaks with three culture-confirmed cases each were associated with person-to-person transmission in child daycare facilities. Five cases of HUS, including one death, resulted from the daycare outbreaks. A water-borne outbreak of E. coli O157:H7 at a swimming beach in the Twin Cities metropolitan area resulted in 10 culture-confirmed cases. MDH followed-up on five cases of the swimming beach outbreak who had reported attending daycare during or shortly after their illness; this resulted in identification of one of the aforementioned small daycare outbreaks. Monitored coliform levels in the lake remained above regulatory cut-offs for the remainder of the summer, and the beach was not reopened for the season. A food-borne outbreak in a Chinese buffet-style restaurant, identified through routine surveillance, resulted in five culture-confirmed cases. All five case-patients were hospitalized, and one developed HUS. The likely cause was cross-contamination of raw meats with vegetables and other ready-to-eat foods. Finally, an outbreak of infections with E. coli O157:H7 and other enteric pathogens occurred at a farm day camp for children. Transmission of the pathogens was associated with direct contact with calves.
In 2001, 22 cases of HUS were reported to MDH, resulting in four deaths in patients aged 3, 4, 6 and 73 years, respectively. The case fatality rate was 18%. During 1997-2001, the mean annual number of HUS cases reported was 16, and the mean case fatality rate was 11%. The median age of HUS case-patients in 2001 was 4 years (range, 9 months to 73 years), and 14 (64%) were female. All 22 case-patients were hospitalized, with a median hospital stay of 10 days (range, 2 to 46 days). Twelve (55%) cases occurred in August and September. Four of the six outbreak-associated HUS cases also occurred during these months.
All 22 HUS cases were post-diarrheal. E. coli O157:H7 was isolated from 15 (68%) cases, including two of the fatal cases. Three cases were due to E. coli O111; one of these cases was culture-confirmed, and all three were positive for serum antibodies. The E. coli O111 cases occurred in siblings, and one case was fatal. In 2000, one HUS case reported to MDH was due to E. coli O111. The HUS cases due to E. coli O111 in 2000 and 2001 represent the first post-diarrheal HUS cases in Minnesota with a documented etiology other than E. coli O157:H7.