Epidemiology

Globally, an estimated 700,000 to one million new cases occur annually; 600,000 to one million new cases of cutaneous leishmaniasis, and 50,000 to 90,000 new cases of visceral leishmaniasis.[14]

Leishmaniasis occurs in 99 countries or territories in the tropics and subtropics, including the southern US, southern Europe, and most of Central and South America. Fewer than 100 autochthonous cases have been reported in the US in the past 100 years.[15] Leishmaniasis is a major health problem in four regions:[16]

  • The Americas

  • East Africa

  • North Africa

  • West and South-East Asia.

Cutaneous leishmaniasis (CL)

  • CL is the most common leishmanial syndrome worldwide. In 2023, 272,098 new cases of CL (271,705 autochthonous and 393 imported) were reported globally. Cases have varied from as few as 185,454 in 2014 to the highest peak of 280,679 in 2019. The number of cases dropped during the COVID-19 pandemic, with levels approaching pre-COVID-19 levels again in 2023.[16]

    • Ninety countries are endemic for CL. The majority of cases were reported from the Eastern Mediterranean region (81%) and the region of the Americas (13%). The two epidemiological hotspots were the Eastern Mediterranean region and Algeria.

    • Eleven countries represented 91% of CL cases: Afghanistan; Algeria; Brazil; Colombia; Iran (Islamic Republic of); Iraq; Pakistan; Peru; Sri Lanka; Syrian Arab Republic; and Yemen.

    • Most cases occurred in females (56%) and children aged <5 years (51%).

  • The global number of cases has been increasing, due to the adaptation of transmission cycles to peridomestic environments; the spread to previously non-endemic areas due to urbanisation and deforestation; limited or non-existent vector or reservoir control programmes; improved diagnosis and case notification; increased detection of leishmaniasis associated with opportunistic infections (e.g., HIV infection); and the emergence of antileishmanial drug resistance.[17][18]

  • CL is the form that is most likely to be seen in the US. It has been reported in increasing numbers in the US and UK, most likely due to increased travel to endemic areas as a result of tourism, military duty, or professional work.[19][20][21][22]

  • Large outbreaks (i.e., >200,000 cases) have been associated with sustained periods of conflict and the resulting collapse of health services (e.g., Afghanistan, Syria).[23][Figure caption and citation for the preceding image starts]: Distribution of new cases of cutaneous leishmaniasis (CL) worldwide, 2022WHO https://www.who.int/publications/i/item/who-wer9840-471-487; used with permission [Citation ends].com.bmj.content.model.Caption@25acff6b

Visceral leishmaniasis (VL)

  • VL is the most serious form of the disease and is fatal in most cases if left untreated. In 2023, 11,922 new cases of VL (11,762 autochthonous and 160 imported) were reported globally. The number of cases reported has decreased by 62% overall since 2014.[16]

    • Eighty countries are endemic for VL. The majority of cases were reported from the Eastern Mediterranean region (42%) and the African region (37%). The three epidemiological hotspots were East Africa, Brazil, and the Indian subcontinent.

    • Four countries represented 60% of cases: Brazil; Ethiopia; Kenya; and Sudan. Most cases occurred in males (62%) and people aged ≥15 years (50%).

  • In the US, symptomatic VL is a rare disease found in returning US military service members from Iraq or Afghanistan, or in migrants or visitors from endemic areas.[24][25][26] However, surveillance for asymptomatic Leishmania infantum (synonym: Leishmania chagasi) infection among Iraq-deployed US service members identified a 19.5% infection rate.[27] Foxhounds have been found to be infected by L infantum in eastern states, but autochthonous transmission to humans has yet to be described in the US.[28]

  • VL mainly affects resource-poor people in rural areas in endemic countries. However, several reports have documented its expansion into urban areas (e.g., Brazil).[29]

  • VL has been eliminated in Bangladesh, and it is the first country in the world to be validated for eliminating it as a public health problem.[30][Figure caption and citation for the preceding image starts]: Distribution of new cases of visceral leishmaniasis (VL) worldwide, 2022​WHO https://www.who.int/publications/i/item/who-wer9840-471-487; used with permission [Citation ends].com.bmj.content.model.Caption@dfc09c9

Post-kala-azar dermal leishmaniasis

  • In 2023, 483 new cases of post-kala-azar dermal leishmaniasis were reported globally from seven countries, with 67% of cases reported from India.[16]

Co-infection with leishmaniasis (predominantly VL) and HIV has been reported in at least 42 countries.[15][16]

  • In the period 2014-2023, 3902 cases of VL-HIV co-infection were reported.

  • The introduction of antiretroviral therapy has caused the incidence to decrease substantially in developed countries, but co-infection with HIV is growing in parts of Asia, Latin America, and Africa.

WHO: leishmaniasis country profile Opens in new window

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