Epidemiology

Antibiotic resistance has contributed to more prolonged and widespread outbreaks. Accurate numbers for the annual incidence of shigellosis are difficult to obtain. Although Shigella is a common cause of diarrheal disease, it is not easy to isolate, and patients with milder symptoms often do not seek medical attention and are therefore missed.​

An estimated 188 million cases of shigellosis occurred globally in 2010, with 62.3 million of these in children ages <5 years.[6] In 2016, Shigella was the second most common cause of diarrhea-related mortality worldwide and was responsible for over 212,000 deaths.[3] Mortality rates are highest for children under the ages 5 years, and in countries with lower sociodemographic indices.​​[3]

Between 2013 and 2015, the incidence of Shigella increased by 7% in the US, and was estimated at 4.6 cases per 100,000.[7] In 2016, Shigella sonnei accounted for 80.5% of cases, followed by S flexneri with 12.6% of cases, S boydii with 0.2%, and S dysenteriae with 0.1%.[2] The majority of reported cases occurred in children between 1 and 4 years old.[2] Overall mortality in the US is very low (0.1% in 2016).[7] 

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