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 diarrhoeal 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 aged <5 years.[6] In 2016, Shigella was the second most common cause of diarrhoea-related mortality worldwide and was responsible for over 212,000 deaths.[2]​ Mortality rates are highest for children under the aged 5 years, and in countries with lower sociodemographic indices.​​​[2]

The notification rate of Shigella infection in England and Wales was 4.9 notifications per 100,000 in 2019, a total of 3270 infections.[7]​ Non-travel associated Shigella infection among adults has increased in the UK and accounts for the majority of reported cases.[8] This may be related to increased sexual transmission among men who have sex with men.[9]

Between 2013 and 2015, the incidence of Shigella increased by 7% in the US, and was estimated at 4.6 cases per 100,000.[10] 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%.[3] The majority of reported cases occurred in children between 1 and 4 years old.[3] Overall mortality in the US is very low (0.1% in 2016).[10]

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