# Epidemiology of schistosomiasis
Schistosomiasis is a parasitic disease caused by blood flukes of the genus *Schistosoma*[2](https://www.who.int/en/news-room/fact-sheets/detail/schistosomiasis). It is endemic in 79 countries, and quantitative estimates of its scale differ sharply between estimation systems: the Global Burden of Disease (GBD) 2021 study modeled 151.38 million people infected in 2021, while WHO counted at least 253.7 million people requiring preventive treatment in 2024[1](https://www.sciencedirect.com/science/article/pii/S0001706X24003887) • [2](https://www.who.int/en/news-room/fact-sheets/detail/schistosomiasis). Both systems agree on the geography: roughly nine in ten cases are in Africa, with the remainder in Asia, and the Americas[1](https://www.sciencedirect.com/science/article/pii/S0001706X24003887).
| Key fact | Value |
|---|---|
| People infected (GBD 2021 model) | 151.38 million (95% UI 109.06–198.67 million) in 2021[1](https://www.sciencedirect.com/science/article/pii/S0001706X24003887) |
| People requiring preventive treatment (WHO 2024) | At least 253.7 million; 100.5 million reported treated[2](https://www.who.int/en/news-room/fact-sheets/detail/schistosomiasis) |
| Countries with transmission | 79 (Cabo Verde newly confirmed endemic)[2](https://www.who.int/en/news-room/fact-sheets/detail/schistosomiasis) |
| Global DALYs (GBD 2021) | 1,746,333 (95% UI 1,038,122–2,984,204)[1](https://www.sciencedirect.com/science/article/pii/S0001706X24003887) |
| Global deaths (GBD 2021) | 12,858 (95% UI 11,335–14,388); WHO estimates 14,353 per year, likely underestimated[1](https://www.sciencedirect.com/science/article/pii/S0001706X24003887) • [2](https://www.who.int/en/news-room/fact-sheets/detail/schistosomiasis) |
| Largest country burden | Nigeria, 44.19 million cases in 2021[1](https://www.sciencedirect.com/science/article/pii/S0001706X24003887) |
| Age peak | 15–29 years[8](https://doi.org/10.3390/tropicalmed10020042) |
| Countries validated by WHO for elimination as a public health problem | Zero, as of December 2023[4](https://mectizan.org/wp-content/uploads/2024/05/Global-report-on-neglected-tropical-diseases-2024.pdf) |
## Overview and definitions
Headline numbers for schistosomiasis measure different things. GBD's figure is a modeled estimate of current infection[1](https://www.sciencedirect.com/science/article/pii/S0001706X24003887). A third framing, "at least 230–260 million people estimated to be infected", appears in WHO-affiliated guidance and reviews[12](https://www.mdpi.com/2414-6366/2/3/36) • [13](https://espen.afro.who.int/sites/default/files/content/document/Draft%20manual%20on%20validation%20and%20verification%20of%20elimination%20of%20schistosomiasis%2027.05.25%20-%20Copy.pdf).
The gap between systems is large and unresolved. GBD 2019 estimated 140 million infected where WHO reported 240 million, and the GBD 2019 authors state this discrepancy explicitly[6](https://www.sciencedirect.com/science/article/pii/S147789392400067X). Diagnostic insensitivity is one driver: the Kato-Katz stool test detects only about half of *S. mansoni* infections with a single slide, so modeled and survey-based counts both miss a large "egg-negative/worm-positive" population[10](https://journals.plos.org/plosntds/article?id=10.1371%2Fjournal.pntd.0005953) • [11](https://link.springer.com/article/10.1186/s40249-017-0275-5).
Two clinical forms correspond to different species. Urogenital schistosomiasis is caused mainly by *S. haematobium*, found in Africa, the Middle East, and Corsica. Intestinal schistosomiasis is caused by *S. mansoni* (Africa and the Americas), *S. japonicum* (China, Indonesia, the Philippines), and *S. mekongi* and *S. guineensis*/*S. intercalatum* in more restricted areas[2](https://www.who.int/en/news-room/fact-sheets/detail/schistosomiasis). Around two-thirds of infections in sub-Saharan Africa are urogenital[13](https://espen.afro.who.int/sites/default/files/content/document/Draft%20manual%20on%20validation%20and%20verification%20of%20elimination%20of%20schistosomiasis%2027.05.25%20-%20Copy.pdf).
## Global distribution and species geography
Africa dominates the map. GBD 2021 attributed 84.25% of global cases to Africa (127.54 million), 10.54% to Asia (15.96 million), and 5.15% to the Americas (7.79 million)[1](https://www.sciencedirect.com/science/article/pii/S0001706X24003887); WHO puts at least 93.9% of those needing treatment in Africa[2](https://www.who.int/en/news-room/fact-sheets/detail/schistosomiasis), and the WHO AFRO guidance states about 91% of cases occur in sub-Saharan Africa[13](https://espen.afro.who.int/sites/default/files/content/document/Draft%20manual%20on%20validation%20and%20verification%20of%20elimination%20of%20schistosomiasis%2027.05.25%20-%20Copy.pdf).
The map is not static. Transmission of *S. haematobium* was newly confirmed in Cabo Verde, a country not previously considered endemic[2](https://www.who.int/en/news-room/fact-sheets/detail/schistosomiasis), and locally acquired cases have been reported in Corsica, France, where hybridization between human and animal schistosome parasites is also producing zoonotic infections[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC8293433/).
## By the numbers
GBD 2021 estimated 1,746,333 DALYs globally in 2021, of which Africa bore 87.92%, Asia 7.88%, and the Americas 4.12%[1](https://www.sciencedirect.com/science/article/pii/S0001706X24003887). Deaths were estimated at 12,858 in 2021, down from 20,293 in 1990, with the age-standardized mortality rate falling from 0.46 to 0.15 per 100,000[7](https://www.parasite-journal.org/articles/parasite/full_html/2025/01/parasite240186/parasite240186.html). WHO's own death estimate, 14,353 per year, is described by WHO as likely underestimated and needing reassessment[2](https://www.who.int/en/news-room/fact-sheets/detail/schistosomiasis).
Prevalence has fallen in relative terms even as absolute cases rose: global cases increased from 136.53 million in 1990 to 151.38 million in 2021, while the age-standardized prevalence rate fell from 2,473.94 to 1,914.30 per 100,000[7](https://www.parasite-journal.org/articles/parasite/full_html/2025/01/parasite240186/parasite240186.html). DALYs lost to schistosomiasis fell from over 2.2 million in 2000 to an estimated 1.6 million in 2019, as preventive chemotherapy coverage rose from about 5% to over 60%[9](https://journals.plos.org/plosntds/article?id=10.1371%2Fjournal.pntd.0010575).
## Regional epidemiology and hotspots
Western [Sub-Saharan Africa](https://www.edgepedia.org/sub-saharan-africa) had the most cases of any GBD region, 61.54 million, and the highest age-standardized prevalence, 13,433.55 per 100,000, in 2021[1](https://www.sciencedirect.com/science/article/pii/S0001706X24003887). Within Africa, West Africa had the highest regional prevalence rate (14,308.56 per 100,000) and North Africa the lowest (1,509.2 per 100,000)[8](https://doi.org/10.3390/tropicalmed10020042). Africa's overall age-standardized prevalence fell from 18,495.51 per 100,000 in 1990 to 9,461.76 per 100,000 in 2021[8](https://doi.org/10.3390/tropicalmed10020042).
Three countries dominate the country-level counts: Nigeria with 44.19 million cases in 2021, Ethiopia with 20.95 million and China with 11.46 million[1](https://www.sciencedirect.com/science/article/pii/S0001706X24003887). Mauritius had the highest age-standardized prevalence of any country, 30,746.27 per 100,000[1](https://www.sciencedirect.com/science/article/pii/S0001706X24003887). A systematic review of *S. mansoni* across 2010–2024 found pooled prevalence of 14.8%, with 15.3% in sub-Saharan Africa, 12.4% in South America, and 9.5% in the [Eastern Mediterranean](https://www.edgepedia.org/eastern-mediterranean) region[3](https://www.thelancet.com/journals/eclinm/article/PIIS2589-5370(24)00434-6/fulltext).
## Who is infected: age, sex and exposure
Infection concentrates in adolescents and young adults. GBD 2021 found the heaviest burden in people aged 15–24[1](https://www.sciencedirect.com/science/article/pii/S0001706X24003887), and the Africa-specific analysis found peak prevalence in the 15–29 age group, with male prevalence higher than female in every age group, attributed to more frequent water contact[8](https://doi.org/10.3390/tropicalmed10020042).
WHO describes the affected populations as poor rural communities, agricultural and fishing populations, women doing domestic chores in infested water, and children[2](https://www.who.int/en/news-room/fact-sheets/detail/schistosomiasis). In children the disease causes anemia, stunting, and reduced learning ability, usually reversible with treatment[2](https://www.who.int/en/news-room/fact-sheets/detail/schistosomiasis). The benefit of control has been uneven by age: the schistosomiasis DALY reduction from 2000 to 2019 was 31% in school-aged children and very small in preschool-aged children, who lacked approved treatment for most of that period[9](https://journals.plos.org/plosntds/article?id=10.1371%2Fjournal.pntd.0010575).
## Disease burden and sequelae
Most of the burden is morbidity rather than death: years lived with disability contribute more than years of life lost to the DALY total[6](https://www.sciencedirect.com/science/article/pii/S147789392400067X). Mortality estimates nevertheless span an order of magnitude. GBD puts global deaths at about 12,858 and WHO at 14,353 per year, while a specialist review estimates 280,000 deaths annually in sub-Saharan Africa alone[7](https://www.parasite-journal.org/articles/parasite/full_html/2025/01/parasite240186/parasite240186.html) • [2](https://www.who.int/en/news-room/fact-sheets/detail/schistosomiasis) • [5](https://pmc.ncbi.nlm.nih.gov/articles/PMC8293433/). WHO notes that deaths are hard to estimate because of hidden pathologies such as liver and kidney failure, bladder cancer, and ectopic pregnancies[2](https://www.who.int/en/news-room/fact-sheets/detail/schistosomiasis).
**Female genital schistosomiasis** is a major and contested component of the burden. One review estimates it affects up to 20 million women in sub-Saharan Africa and the Middle East and is linked to increased HIV risk through genital mucosal lesions[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC8293433/); a GBD 2021 Africa analysis estimates up to 56 million affected women, with nearly 20 million new cases projected over the next decade if untreated[8](https://doi.org/10.3390/tropicalmed10020042). The sources do not reconcile these figures. Chronic *S. haematobium* infection also causes squamous cell bladder cancer, with an estimated incidence of 3–4 cases per 100,000 infections[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC8293433/).
## How it compares with other helminth infections
Schistosomiasis and soil-transmitted helminthiases share endemic geography and control strategy. Combined, DALYs lost to the two fell from 6.4 million per year in 2000 to 3.6 million in 2019, a cumulative gain of over 26 million DALYs, as preventive chemotherapy coverage rose from about 5% to over 60%[9](https://journals.plos.org/plosntds/article?id=10.1371%2Fjournal.pntd.0010575). Schistosomiasis alone accounted for roughly 1.6 million of those DALYs in 2019[9](https://journals.plos.org/plosntds/article?id=10.1371%2Fjournal.pntd.0010575). The burden is strongly graded by development: in 2019 the age-standardized DALY rate was 0.9 per 100,000 in high-SDI regions versus 89.4 in low-SDI regions[6](https://www.sciencedirect.com/science/article/pii/S147789392400067X).
## References
1. Global trends of schistosomiasis burden from 1990 to 2021 across 204 countries and territories: Findings from GBD 2021 study. https://www.sciencedirect.com/science/article/pii/S0001706X24003887
2. WHO Schistosomiasis Fact Sheet. https://www.who.int/en/news-room/fact-sheets/detail/schistosomiasis
3. Prevalence of human Schistosoma mansoni infection in endemic regions (2010–2024): a systematic review and meta-analysis. https://www.thelancet.com/journals/eclinm/article/PIIS2589-5370(24)00434-6/fulltext
4. WHO Global report on neglected tropical diseases 2024. https://mectizan.org/wp-content/uploads/2024/05/Global-report-on-neglected-tropical-diseases-2024.pdf
5. Schistosomiasis with a Focus on Africa. https://pmc.ncbi.nlm.nih.gov/articles/PMC8293433/
6. Burden of schistosomiasis in global, regional, and national 1990–2019: GBD 2019 systematic analysis. https://www.sciencedirect.com/science/article/pii/S147789392400067X
7. The impact of schistosomiasis on the Global Disease Burden: a systematic analysis based on the 2021 GBD study. https://www.parasite-journal.org/articles/parasite/full_html/2025/01/parasite240186/parasite240186.html
8. Schistosomiasis Burden and Trend Analysis in Africa: Insights from the Global Burden of Disease Study 2021. https://doi.org/10.3390/tropicalmed10020042
9. Reduction in DALYs lost due to soil-transmitted helminthiases and schistosomiasis from 2000 to 2019. https://journals.plos.org/plosntds/article?id=10.1371%2Fjournal.pntd.0010575
10. Estimating sensitivity of the Kato-Katz technique for the diagnosis of Schistosoma mansoni and hookworm in relation to infection intensity. https://journals.plos.org/plosntds/article?id=10.1371%2Fjournal.pntd.0005953
11. Schistosomiasis is more prevalent than previously thought. https://link.springer.com/article/10.1186/s40249-017-0275-5
12. Neglected Tropical Diseases: Epidemiology and Global Burden. https://www.mdpi.com/2414-6366/2/3/36
13. Draft manual on validation and verification of elimination of schistosomiasis (WHO AFRO ESPEN). https://espen.afro.who.int/sites/default/files/content/document/Draft%20manual%20on%20validation%20and%20verification%20of%20elimination%20of%20schistosomiasis%2027.05.25%20-%20Copy.pdf
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*Topic: Encyclopedia › Life and health › Animals › Invertebrates › Other invertebrate lineages › Flatworms › Trematoda (flukes) › Schistosomiasis › Epidemiology and geography*
*Initially written Sep 17, 2026 · Edited: Oct 11, 2026; Oct 15, 2026; Oct 21, 2026*
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License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license