Epidemiology

Giardia is one of the most commonly diagnosed intestinal protozoa.​​[11][12]​​​ It is commonly identified in tropical and temperate regions of the world and is more prevalent in rural areas, and in low- and middle- income countries where exposure is nearly universal. 

Nearly 15,000 cases of Giardiawere reported in the US in 2019.[13] Most cases are sporadic (non-outbreak). Outbreaks are increasingly less common in the US, and accounted for 241 cases in 2019.​[13] However, there is wide variation in surveillance efforts in the US; one analysis noted that at least 4 states, and up to 9 states, did not participate in giardiasis case reporting during the period 1995-2016.[14]

Those most likely to acquire giardiasis include:[1]​[14][15]​​​​[16]​​[17]

  • Children less than 4 years of age

  • Individuals in contact with children in diapers

  • Individuals drinking water from, or swimming in a, river, lake, or stream (e.g., campers, hunters, backpackers)

  • International travelers

  • Tourists to endemic areas

Travel destinations with higher risk include: Africa (North Africa and sub-Saharan Africa), the Caribbean, Central and South America, South-Central Asia, Eastern Europe, and the Middle East.[1]

In adults, exposure risks may vary between men and women, and males may be at greater risk of infection.[14][18]

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