The Incidence of Shigella Infection
How common are Shigella infections and Shigella outbreaks?
The number of shigellosis cases reported annually to the Centers for Disease Control and Prevention (CDC) has varied over the past several years, from more than 17,000 during 1978–2003, to an all-time low of 14,000 in 2004, to almost 20,000 in 2007. [11, 19] But a majority of cases go undiagnosed or unreported. [12, 16, 37] In one study done in Oregon, 430 confirmed Shigella cases from July 1995 through June 1998 were examined.  Among the several findings about those most likely to fall ill was the following:
Of 430 isolates, 410 were identified to the species level: Shigella sonnei accounted for 55% of isolates, and Shigella flexneri, for 40%. The overall annual incidence of shigellosis was 4.4 cases per 100,000 population. Children aged [less than] 5 years (annual incidence, 19.6 cases per 100,000 population) and Hispanics (annual incidence, 28.4 cases per 100,000 population) were at highest risk.