African trypanosomiasis is an insect-borne parasitic infection of humans and other animals caused by protozoan parasites of the Trypanosoma brucei species complex, transmitted through the bite of an infected tsetse fly [1][2][3]. Two subspecies are responsible for human disease: T. b. gambiense, which accounts for over 92% of human cases and is primarily transmitted between humans, and T. b. rhodesiense, which is zoonotic with animals such as cattle serving as reservoirs [2][3].
Disease overview
ParasiticAfrican trypanosomiasis
非洲锥虫病
Evidence-backed informationEN 5/7 applicable sections · ZH 5/7 applicable sectionsUpdated Sep 3, 2026
Human African trypanosomiasis (sleeping sickness) is an insect-borne parasitic disease caused by Trypanosoma brucei gambiense or T. b. rhodesiense and transmitted by tsetse flies in sub-Saharan Africa [1][2][3]. The disease is almost invariably fatal without treatment and caused devastating epidemics during the 20th century, but sustained case detection, treatment, and vector control have reduced reported incidence to historically low levels [1][2]. Elimination as a public health problem has been achieved, with elimination of gambiense transmission targeted for 2030 [2]. Because sporadic cases are also reported from non-endemic countries, the disease should be considered in returning travellers, migrants, and expatriates with compatible exposures [1].
Read the full clinical and epidemiological profile6
During the first stage of disease, parasites replicate in the blood and lymph, producing fever, headache, itchiness, and joint pains roughly one to three weeks after the infective bite [3]. Weeks to months later the parasite crosses the blood–brain barrier, and the second stage is marked by neurological manifestations such as confusion, poor coordination, numbness, and disturbed sleep, progressing to brain dysfunction if untreated [4][3]. T. b. gambiense typically causes a chronic infection that may take months to years to become symptomatic, whereas T. b. rhodesiense produces symptoms within weeks to months; in the absence of treatment the disease almost always results in death [1][4][3].
African trypanosomiasis is endemic in parts of sub-Saharan Africa, where it remains a considerable burden on rural communities, most notably in central Africa, and has been recorded in 37 countries in the region [1][3]. Sustained control efforts reduced reported cases to fewer than 3,000 in 2015, an 86% reduction from the year 2000, and the disease is targeted for elimination by WHO, with elimination of gambiense transmission targeted for 2030 [1][2][3]. The disability-adjusted life-years lost due to sleeping sickness have been estimated at around 2.0 million, and an estimated 55 million and 6 million people were at risk for gambiense and rhodesiense disease respectively from 2010 to 2014 [3]. The epidemiology reflects the interaction between the trypanosome parasite, the tsetse fly vector, and the human or animal host, and animal reservoirs may contribute to persistence and resurgence in historic foci [3].
Human African trypanosomiasis is transmitted through the bite of an infected tsetse fly, the insect vector that maintains the Trypanosoma brucei parasite in sub-Saharan Africa [1][2][3]. T. b. gambiense is transmitted primarily between humans, which makes it largely anthroponotic, while T. b. rhodesiense is predominantly zoonotic, with accidental human spillover from animal reservoirs such as cattle [3]. Long-lasting infection in the mammalian host is required to sustain transmission, and the parasite has evolved mechanisms to evade host immunity while preserving host viability for vector uptake [4].
Because no vaccine is available, prevention and control rely on case detection and treatment, vector control, and individual protection against tsetse fly bites [1][2][3]. Population screening with blood tests for T. b. gambiense in at-risk communities helps to interrupt transmission and prevent progression to severe disease, and the introduction of simple rapid diagnostic tests has facilitated screening in primary health-care facilities [2][3]. Vector control measures—including spraying of insecticides, release of sterilized tsetse flies, and in some areas tiny target-based interventions—have substantially reduced incidence, while personal protection through insect repellents and protective clothing lowers individual exposure [1][2][3].
- 1Büscher P et al. Human African trypanosomiasis. Lancet. 2017 Nov 25. PMID: 28673422. doi: 10.1016/S0140-6736(17)31510-6.PubMed: https://pubmed.ncbi.nlm.nih.gov/28673422/
- 2Lejon V et al. Human African trypanosomiasis. Lancet. 2025 Mar 15. PMID: 40089378. doi: 10.1016/S0140-6736(25)00107-2.PubMed: https://pubmed.ncbi.nlm.nih.gov/40089378/
- 3Wikipedia contributors. African trypanosomiasis - Wikipedia [Internet]. Wikipedia. cited 3 Sept 2026.Available from: https://en.wikipedia.org/wiki/African_trypanosomiasis
- 4Pays E et al. The Pathogenesis of African Trypanosomiasis. Annu Rev Pathol. 2023 Jan 24. PMID: 36055769. doi: 10.1146/annurev-pathmechdis-031621-025153.PubMed: https://pubmed.ncbi.nlm.nih.gov/36055769/
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Clinical Microbiology and Infection
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