During 2002, 222 culture-confirmed cases of Shigella infection (4.5 per 100,000 population) were reported (Figure 2). This represents a 55% decrease from the 493 cases reported in 2001, a 75% decrease from the 904 cases reported in 2000 (the largest annual number of cases ever reported in Minnesota), and a 33% decrease from the median number of cases reported annually from 1997 to 2001 (median, 331 cases; range, 138 to 904).
In 2002, Shigella sonnei accounted for 179 (81%) cases, S. flexneri for 32 (14%), S. boydii for two (1%), and S. dysenteriae for one (<1%); eight isolates were not serotyped. Case-patients ranged in age from 3 months to 77 years (median, 10 years). Forty-eight percent of case-patients were less than 10 years of age; children less than 5 years of age accounted for 26% of cases. Thirty-two (14%) case-patients were hospitalized. Seventysix percent of case-patients resided in the seven-county Twin Cities metropolitan area, with 45% of all case-patients residing in Hennepin County.
Six outbreaks of shigellosis were identified in 2002; all were person-toperson outbreaks due to S. sonnei. These outbreaks resulted in at least 75 illnesses, including 36 culture-confirmed cases (representing 20% of all reported S. sonnei cases). Four of the outbreaks occurred in child daycare settings, and two occurred in elementary schools. In addition, two culture-confirmed S. sonnei cases reported in 2002 were part of a S. sonnei outbreak in an elementary school that began in December 2001.
Every tenth Shigella isolate received at MDH was tested for antimicrobial resistance, but only one isolate from each outbreak was included. Twenty isolates were tested in 2002; 90% of isolates were resistant to ampicillin, and 20% were resistant to trimethoprim-sulfamethoxazole. Twenty percent of isolates tested were resistant to both ampicillin and trimethoprim-sulfamethoxazole.