Epidemiology

There is a higher incidence of amoebiasis in developing versus developed countries. It occurs most commonly in areas of poor sanitation.[9]​ Most amoebic infections occur in Central and South America, Africa, and Asia.[2]​ Entamoeba histolytica infection in the US is seen most commonly in immigrants and travellers from endemic areas, with approximately 3000 cases seen annually.[4] In most cases, disease presents within the first year of return to or arrival in the country. Long-term travellers (duration >6 months) are much more likely than short-term travellers (duration <1 month) to develop infection.[9]

Intestinal infection with E histolytica affects all ages and both sexes equally. However, 90% of amoebic liver abscesses occur in men aged 20 to 40 years.[1][2][3][4][5]​​​​​ The increased risk of amoebiasis-related mortality in men may reflect the increased prevalence of amoebiasis among men who have sex with men (MSM), although it was previously reported that the non-pathogenic amoeba E dispar is more common in this setting than E histolytica.[1][2][10]​​​​​​[11]​ Other groups at greater risk for severe disease include people who are pregnant, immunocompromised, or receiving corticosteroids, people with diabetes, and those who consume alcohol.[9]

Outbreaks in institutions, particularly those for people who are intellectually disabled, have occurred.[1][2] MSM, oral-anal sexual contact, lower educational achievement, and older age were associated with increased risk for amoebiasis among people seeking voluntary counselling and testing for HIV infection in Taiwan.[12] Comorbid HIV infection and past history or positive serology of syphilis have also been associated with increased prevalence of amoebiasis. The reasons for these associations are unclear, but may reflect similar risk factors for these infections.[10][13][14][15]​​

Globally, E histolytica accounts for 2% to 4% of cases of diarrhoea presenting to a hospital or a clinic.[1][2][3][4][5][6][7]

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