Spatial-temporal distribution of visceral leishmaniasis in Rio de Janeiro, Brazil, 2001-2020: expansion and challenges.

Background: Visceral leishmaniasis results from complex interactions among humans, dogs and environment. Brazil accounts for 97% of cases in the Americas.

Methods: Twenty years (2001-2020) of the endemic disease in the state of Rio de Janeiro were studied. Incidence, lethality, sociodemographic and clinical characteristics were investigated, complemented with spatial methodologies (kernel and clusters).

Results: Ninety-seven human cases and 625 dogs were reported. Of the 92 cities, 22 were human endemic areas. The state had a low incidence level (0.6 per 100 000). Lethality was higher compared with the Brazilian average. More than 90% of infections occurred in urban areas. Most cases (66%) occurred in men. The predominant age groups were 0-4 y (28.7%) and 20-39 y (32.9%). Fever (89.5%), splenomegaly (83.2%) and hepatomegaly (76.8%) were the main clinical manifestations. Spatial analysis showed a displacement of the human endemic: in the first decade (2001-2010), cases were concentrated in the Metropolitan region, and in the second decade (2011-2020) in the Médio Paraíba region of the state. Most of the endemic area (56.4%) had canine infections without reported human cases.

Conclusions: Disorderly urbanisation and precarious living conditions favour the transmission of the disease. Changes in the environment and migratory processes contribute to its expansion.