Spatial distribution pattern of new leprosy cases under 15 years of age and their contacts in Sobral, Ceará, Brazil.

This study's objective was to analyze the spatial distribution pattern of new leprosy cases under 15 years and their contacts. A cross-sectional descriptive study covering sociodemographic characteristics and spatial analysis was carried out. The participants were from the city of Sobral, Ceará and the study was conducted between August 2014 and September 2015. Contacts were identified by the persons responsible for the children. Seropositivity was determined with the NDO-LID antigen, and positive cases were plotted on Voronoi polygons. Nine new cases of leprosy under 15 years of age have been found. The average number of people living with the cases was higher than the number of people living with non-household contacts. All household contacts were aware of other leprosy cases and had a higher rate of seropositive tests than non-household contacts. The index cases lived in the poorest regions of the municipality and hyper-endemic areas. Spatial analysis revealed a cluster of subclinical infection within a radius of 102 meters, suggesting that non-household transmission is related to proximity with seropositive individuals. In conclusion, the search for new leprosy cases cannot be restricted to household contacts.

Spatial distribution pattern of new leprosy cases under 15 years of age and their contacts in Sobral, Ceará, Brazil / Distribuição espacial de novos casos de hanseníase em menores de 15 anos e de seus contatos em Sobral, Ceará, Brasil

Abstract This study's objective was to analyze the spatial distribution pattern of new leprosy cases under 15 years and their contacts. A cross-sectional descriptive study covering sociodemographic characteristics and spatial analysis was carried out. The participants were from the city of Sobral, Ceará and the study was conducted between August 2014 and September 2015. Contacts were identified by the persons responsible for the children. Seropositivity was determined with the NDO-LID antigen, and positive cases were plotted on Voronoi polygons. Nine new cases of leprosy under 15 years of age have been found. The average number of people living with the cases was higher than the number of people living with non-household contacts. All household contacts were aware of other leprosy cases and had a higher rate of seropositive tests than non-household contacts. The index cases lived in the poorest regions of the municipality and hyper-endemic areas. Spatial analysis revealed a cluster of subclinical infection within a radius of 102 meters, suggesting that non-household transmission is related to proximity with seropositive individuals. In conclusion, the search for new leprosy cases cannot be restricted to household contacts.

Resumo O objetivo deste estudo foi analisar o padrão de distribuição espacial de novos casos de hanseníase em menores de 15 anos e seus contatos. Estudo transversal, descritivo, abrangendo características sociodemográficas e análise espacial. Os participantes eram de Sobral, Ceará e o estudo foi realizado entre agosto de 2014 e setembro de 2015. Os contatos foram identificados pelos responsáveis pelas crianças. A soropositividade foi determinada com o antígeno NDO-LID e os casos positivos foram plotados em polígonos de Voronoi. Nove novos casos de hanseníase em menores de 15 anos foram encontrados. O número médio de pessoas que conviviam com os casos foi superior ao número de pessoas que conviviam com contatos não domiciliares. Todos os contatos domiciliares sabiam de outros casos de hanseníase e apresentaram maior taxa de testes soropositivos do que os contatos não domiciliares. Os casos índice residiam nas regiões mais pobres do município e em áreas hiperendêmicas. A análise espacial revelou um agrupamento de infecção subclínica em um raio de 102 metros, sugerindo que a transmissão não domiciliar está relacionada à proximidade com indivíduos soropositivos. Concluindo, a busca por novos casos de hanseníase não pode se restringir aos contatos domiciliares.

A social network approach for the study of leprosy transmission beyond the household.

BACKGROUND: Mycobacterium leprae was the first microorganism directly associated with a disease, however, there are still important gaps in our understanding of transmission. Although household contacts are prioritized, there is evidence of the importance of extrahousehold contacts. The goal of this article is to contribute to our understanding of the transmission of leprosy ex-household. METHODS: We compare co-location data of 397 leprosy cases and 211 controls drawn from the Centro de Dermatologia Sanitária D. Libânia in Fortaleza, Brazil. We collected lifetime geolocation data related to residence, school attendance and workplace and developed novel methods to establish a critical distance (Rc) for exposure and evaluated the potential for transmission for residence, school and workplace. RESULTS: Our methods provide different threshold values of distance for residence, school and workplace. Residence networks demonstrate an Rc of about 500 m. Cases cluster in workplaces as well. Schools do not cluster cases. CONCLUSIONS: Our novel network approach offers a promising opportunity to explore leprosy transmission. Our networks confirm the importance of coresidence, provide a boundary and suggest a role for transmission in workplaces. Schools, on the other hand, do not demonstrate a clustering of cases. Our findings may have programmatic relevance.