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. There were 18,004 confirmed cases of giardiasis in the EU in 2019.[13]

It is the most common gut parasite in the UK. According to Public Health England there were 3342 laboratory reports of Giardia in 2008; this rose to 4793 in 2017.[14]

Nearly 15,000 cases of Giardiawere reported in the US in 2019.[15] Most cases are sporadic (non-outbreak). Outbreaks are increasingly less common in the US, and accounted for 241 cases in 2019.​[15]​​ 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.[16]

Those most likely to acquire giardiasis include:[1]​[16][17]​​​​[18]​​[19]

  • Children less than 4 years of age

  • Individuals in contact with children in nappies

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

  • International travellers

  • 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.[16][20]

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