*Rate per 100,000 population based on the U.S. Census Bureau’s population data as of July 1, 2003
Shigellosis is a bacterial disease transmitted by the fecal-oral route, usually through hands contaminated with feces. It can also be transmitted through contaminated food and water or through oral-anal sex practices. Shigellosis is highly communicable, as only 10-100 organisms must be ingested to establish infection. Shigella bacteria infect only humans.
In 2003, 201 cases of shigellosis were reported in Indiana, for a case rate of 3.2 per 100,000 population (Table 1). This represents an increase from the incidence rate in 2002 (2.2), although the rate is still below the incidence rate for 2001 (4.1). Figure 1 shows the number of reported cases per year for 1999-2003. The incidence of shigellosis peaked during the summer and fall months (Figure 2). As shown in Figure 3, age-specific rates were highest among preschoolers aged 1-4 years (12.1), followed by children aged 5-9 years (9.5), and infants aged less than 1 year (6.0). Females (3.6) were more likely to be reported than males (2.9). The rate of illness among blacks (12.8) was over eight times higher than whites (1.5) and five times the rate for other races (2.5).
The incidence rates were highest among the following counties reporting five or more cases:
Noble (21.2), Lake (13.1), and Marion (4.9). Figure 4 shows Indiana counties reporting five or more cases.
In 2003, the serotype was determined for 147 (73%) of the 201 reported shigellosis cases. Shigella sonnei accounted for 131 (89%) of the serotyped cases. Fifteen cases were serotyped as Shigella flexneri, and 1 case was serotyped as Shigella boydii. There were no reported cases of Shigella dysenteriae in 2003.
One outbreak of shigellosis was reported in 2003 in Tippecanoe County. At least nine children and one staff member of an in-home daycare center developed symptoms compatible with shigellosis over a period of several weeks. The symptoms were attributed to “flu” or underlying gastrointestinal conditions; and therefore, these cases were not initially reported or excluded. One child and the staff member were confirmed positive for Shigella sonnei. Any child or staff member testing positive for shigellosis was immediately excluded until five days of antibiotic therapy were completed or two negative stool specimens were submitted. Other prevention measures, such as hand washing, glove use during diaper changes, proper disinfection of surfaces and toys, were also implemented.