Giardiasis

Giardiasis is a parasitic disease caused by the protozoan Giardia lamblia, also referred to in the sources as Giardia intestinalis ^[1][2]. One source characterizes the organism as a non-invasive protozoan infecting the upper small intestine ^[2]. The disease is presented in the literature as a common enteric infection with both symptomatic and asymptomatic forms, but the provided sources do not supply formal case-definition criteria ^[1][2].

The source material describes giardiasis as causing acute, watery diarrhea, and also notes that symptomatic cases may present with acute or chronic diarrhea ^[2][1]. Many infections are asymptomatic; one source states that approximately 50 to 75% of infected children have no symptoms ^[1]. Most symptomatic infections resolve spontaneously, but chronic disease can occur, and post-infectious sequelae including irritable bowel syndrome and food allergies have been reported after resolution ^[2]. Source-backed detail on other clinical manifestations, complications, or duration of illness is not yet available ^[1][2].

Giardiasis is described as an important cause of waterborne and foodborne diarrhea and is associated with daycare center outbreaks and traveler’s diarrhea ^[1]. One source gives an annual estimate of 280 million people affected by giardiasis worldwide ^[2]. The provided sources identify higher-risk contexts including daycare settings, childcare work, institutionalized living, travel in endemic areas, and exposure to contaminated or recreational water ^[1]. No additional geographic distribution, seasonality, or routine surveillance burden is stated in the source snippets beyond these outbreak and exposure contexts ^[1][2].

The sources identify fecal-oral transmission as the main route, frequently through ingestion of contaminated water or food, and also through person-to-person spread ^[1]. Exposure to recreational water is explicitly mentioned as a risk context, which is consistent with the contaminated-water pathway described in the sources ^[1]. Source-backed detail on environmental persistence, infectious dose, or other transmission mechanisms is not yet available ^[1].

The source snippets identify children in daycare settings, childcare workers, institutionalized individuals, travelers in endemic areas, and people exposed to contaminated or recreational water as groups with increased infection risk ^[1]. Additional risk factors named in the sources include immunodeficiency, cystic fibrosis, and oral-anal sex ^[1]. Asymptomatic infection is common, especially in children, so risk can be present even when overt illness is absent ^[1][2].

The provided sources do not give a formal prevention guideline or intervention schedule, so source-backed detail on specific preventive measures is limited ^[1][2]. The evidence base does, however, point to exposure control through avoidance of contaminated water and food and reduction of person-to-person spread in settings such as daycare and institutional care ^[1]. Because travel-related illness is highlighted, prevention in practice should be read as risk reduction in endemic travel and water-exposure contexts, but the snippets do not specify any particular public-health regimen ^[1].

In surveillance terms, giardiasis should be read as an enteric parasitic infection that may appear as sporadic waterborne or foodborne illness, clustered daycare outbreaks, or travel-associated diarrhea ^[1]. The large asymptomatic fraction and the possibility of chronic or post-infectious outcomes mean that detected case counts may underrepresent true infection burden ^[2][1]. Source-backed detail on reporting thresholds, laboratory confirmation algorithms, or case classification is not yet available ^[1][2].

1. 1 Leung AKC et al. Giardiasis: An Overview. Recent Pat Inflamm Allergy Drug Discov. 2019. PMID: 31210116. doi: 10.2174/1872213X13666190618124901. PubMed: https://pubmed.ncbi.nlm.nih.gov/31210116/
2. 2 Einarsson E et al. An up-date on Giardia and giardiasis. Curr Opin Microbiol. 2016 Dec. PMID: 27501461. doi: 10.1016/j.mib.2016.07.019. PubMed: https://pubmed.ncbi.nlm.nih.gov/27501461/
3. 3 McFarland LV et al. Systematic review and meta-analysis of Saccharomyces boulardii in adult patients. World J Gastroenterol. 2010 May 14. PMID: 20458757. doi: 10.3748/wjg.v16.i18.2202. PubMed: https://pubmed.ncbi.nlm.nih.gov/20458757/
4. 4 Giardiasis. Gastroenterology Nursing. 1992. doi: 10.1097/00001610-199206000-00009. DOI: https://doi.org/10.1097/00001610-199206000-00009
5. 5 Giardiasis. Netter’s Infectious Diseases. 2012. doi: 10.1016/b978-1-4377-0126-5.00076-8. DOI: https://doi.org/10.1016/b978-1-4377-0126-5.00076-8
6. 6 Giardiasis. Turkish Journal of Medical Sciences. 1996. doi: 10.55730/1300-0144.5257. DOI: https://doi.org/10.55730/1300-0144.5257

ICD-10

ICD-11

Total cases

161K

Peak month

2007-09

Coverage

3 reporting countries · 2012-09-14 → 2026-06-20