Mônica de Avelar Figueiredo Mafra Magalhães

Spatial Evaluation and Modeling of Dengue Seroprevalence and Vector Density in Rio de Janeiro, Brazil

Background Rio de Janeiro, Brazil, experienced a severe dengue fever epidemic in 2008. This was the worst epidemic ever, characterized by a sharp increase in case-fatality rate, mainly among younger individuals. A combination of factors, such as climate, mosquito abundance, buildup of the susceptible population, or viral evolution, could explain the severity of this epidemic. The main objective of this study is to model the spatial patterns of dengue seroprevalence in three neighborhoods with different socioeconomic profiles in Rio de Janeiro. As blood sampling coincided with the peak of dengue transmission, we were also able to identify recent dengue infections and visually relate them to Aedes aegypti spatial distribution abundance. We analyzed individual and spatial factors associated with seroprevalence using Generalized Additive Model (GAM). Methodology/Principal Findings Three neighborhoods were investigated: a central urban neighborhood, and two isolated areas characterized as a slum and a suburban area. Weekly mosquito collections started in September 2006 and continued until March 2008. In each study area, 40 adult traps and 40 egg traps were installed in a random sample of premises, and two infestation indexes calculated: mean adult density and mean egg density. Sera from individuals living in the three neighborhoods were collected before the 2008 epidemic (July through November 2007) and during the epidemic (February through April 2008). Sera were tested for DENV-reactive IgM, IgG, Nested RT-PCR, and Real Time RT-PCR. From the before–after epidemics paired data, we described seroprevalence, recent dengue infections (asymptomatic or not), and seroconversion. Recent dengue infection varied from 1.3% to 14.1% among study areas. The highest IgM seropositivity occurred in the slum, where mosquito abundance was the lowest, but household conditions were the best for promoting contact between hosts and vectors. By fitting spatial GAM we found dengue seroprevalence hotspots located at the entrances of the two isolated communities, which are commercial activity areas with high human movement. No association between recent dengue infection and households high mosquito abundance was observed in this sample. Conclusions/Significance This study contributes to better understanding the dynamics of dengue in Rio de Janeiro by assessing the relationship between dengue seroprevalence, recent dengue infection, and vector density. In conclusion, the variation in spatial seroprevalence patterns inside the neighborhoods, with significantly higher risk patches close to the areas with large human movement, suggests that humans may be responsible for virus inflow to small neighborhoods in Rio de Janeiro. Surveillance guidelines should be further discussed, considering these findings, particularly the spatial patterns for both human and mosquito populations.

Temporal Distribution of Aedes aegypti in Different Districts of Rio De Janeiro, Brazil, Measured by Two Types of Traps

ABSTRACT Dengue dynamics in Rio de Janeiro, Brazil, as in many dengue-endemic regions of the world, is seasonal, with peaks during the wet-hot months. This temporal pattern is generally attributed to the dynamics of its mosquito vector Aedes aegypti (L.). The objectives of this study were to characterize the temporal pattern of Ae. aegypti population dynamics in three neighborhoods of Rio de Janeiro and its association with local meteorological variables; and to compare positivity and density indices obtained with ovitraps and MosquiTraps. The three neighborhoods are distinct in vegetation coverage, sanitation, water supply, and urbanization. Mosquito sampling was carried out weekly, from September 2006 to March 2008, a period during which large dengue epidemics occurred in the city. Our results show peaks of oviposition in early summer 2007 and late summer 2008, detected by both traps. The ovitrap provided a more sensitive index than MosquiTrap. The MosquiTrap detection threshold showed high variation among areas, corresponding to a mean egg density of ≈25–52 eggs per ovitrap. Both temperature and rainfall were significantly related to Ae. aegypti indices at a short (1 wk) time lag. Our results suggest that mean weekly temperature above 22–24°C is strongly associated with high Ae. aegypti abundance and consequently with an increased risk of dengue transmission. Understanding the effects of meteorological variables on Ae. aegypti population dynamics will help to target control measures at the times when vector populations are greatest, contributing to the development of climate-based control and surveillance measures for dengue fever in a hyperendemic area.

The spatial distribution of Aedes aegypti and Aedes albopictus in a transition zone, Rio de Janeiro, Brazil

Dengue fever has become the most important vector-borne viral disease in Brazil. Human facilitated transport of desiccation-resistant eggs has led to its two most important vectors, Aedes aegypti and Ae. albopictus, becoming widespread. In this paper, we report seasonal and spatial variation in larval abundances of Ae. aegypti and Ae. albopictus across a small-scale transition zone between an urban area and an urban wooded/forested area within Rio de Janeiro, Brazil. We installed 400 ovitraps across 10 sites with different human population densities and vegetation coverage. Eggs and larvae were collected for three weeks during the wet and dry seasons of 2002 and 2003. Ae. albopictus was predominantly found in the forested areas of the study site whereas in the urbanized area Ae. aegypti was more abundant. Both species peaked during the wet season. This distribution pattern, which may reflect adult flight range, may favor the co-occurrence of larvae of these species in a small-scale urban/urban forest transition zone.

Esporotricose urbana: epidemia negligenciada no Rio de Janeiro, Brasil

In the scientific literature, sporotrichosis has traditionally been associated with agricultural work, since the causative agent is found naturally in the soil. However, cases have been reported recently in an urban area, related to zoonotic transmission. The current study aimed to contribute to knowledge on sporotrichosis in an urban area through an exploratory analysis of its socio-spatial distribution in Rio de Janeiro, Brazil, from 1997 to 2007, identifying the areas with the heaviest transmission. The database from the Health Surveillance Service at the Evandro Chagas Institute for Clinical Research, Oswaldo Cruz Foundation, was used to estimate incidence rates and spatial distribution. During the study period, 1,848 cases of sporotrichosis were reported, predominantly in adult women not currently in the labor market. The leading source of infection was wounds caused by domestic cats, which contributed to the spread of sporotrichosis in this urban area. Georeferencing of 1,681 cases showed a transmission belt along the border between the city of Rio de Janeiro and the adjacent municipalities in the Greater Metropolitan Area.

Georreferenciamento de dados de saúde na escala submunicipal: algumas experiências no Brasil

This work describes experiences in geocoding health data in Brazilian municipalities, analyzed according to the availability and update of cartographic databases and the treatment given to addresses data in health information systems (SIS). The diversity of current geocoding strategies in Brazil results of local conditions on which these projects are developed, presenting variable efficiency and accuracy for health event location. The authors suggest strategies to capture and store addresses data in SIS, compatible with the existent street registries, as well as the development of programs and scripts to search and link these two databases.

Heterogeneidade espacial da dengue em estudos locais, Niterói, RJ

OBJETIVO: Analisar a ocorrencia espacial e temporal da dengue e sua associacao com a heterogeneidade de caracteristicas do ambiente urbano. METODOS: Foram georreferenciados 1.212 casos de dengue registrados no Sistema de Informacao de Agravos de Notificacao entre 1998 e 2006, no municipio de Niteroi, RJ, segundo setores censitarios. Os setores foram classificados em areas homogeneas para a ocorrencia da doenca: favela, estaleiro e urbano. Os casos foram agrupados em cinco periodos: dois interepidemicos 1998-2000 e 2003-2005; tres epidemicos 2001, 2002 e 2006 e analisados por meio de operacoes entre camadas em ambiente sistema de informacao geografica. Para identificacao de conglomerados com maior intensidade de casos, utilizou-se o metodo de kernel. O metodo de varredura espacial de Kulldorff foi usado para confirmacao estatistica desses clusters. RESULTADOS: Do total de casos, 57% eram do sexo feminino. As faixas etarias com maior concentracao de casos foram de 20-29 anos (20,5%) e de 30-39 anos (17,7%). O setor favela morro apresentou somente 11% dos domicilios atendidos por servico de coleta de lixo, o maior percentual de nao alfabetizados (8,7%) e de chefes de familia com rendimentos menores de 1 salario minimo (29,5%). Os casos permaneceram nos setores denominados favelas. No primeiro ano epidemico e nos periodos interepidemicos o maior numero de casos estava situado nos setores favelas morro e favela plana; no segundo e terceiro ano de epidemia, situavam-se no setor favela plana. CONCLUSOES: A parcela economicamente ativa foi a mais atingida na area de estudo. Os setores censitarios mostram heterogeneidade espacial em relacao as condicoes de vida e dentro de alguns setores, ha diferenciais na distribuicao espacial e temporal do risco de ocorrencia da dengue.OBJECTIVE To analyze the spatial and temporal occurrence of dengue fever and its association with the heterogeneity of urban environment characteristics. METHODS A total of 1,212 dengue cases, recorded in the Information System for Notifiable Diseases (Sinan) between 1998 and 2006, in the city of Niterói, Southeastern Brazil, were georeferenced according to census tracts. These tracts were classified into homogeneous areas for the occurrence of the disease: slum, shipyard and urban area. Cases were grouped into five periods--two inter-epidemic periods (1998-2000 and 2003-2005) and three epidemic periods (2001, 2002 and 2006)--and analyzed using operations between layers in a geographic information system (GIS) environment. The kernel method was used to identify clusters of cases. Kulldorffs spatial scan statistic was used to confirm these clusters statistically. RESULTS Of all cases, 57% were females. Age groups with the highest number of cases were 20-29-years (20.5%) and 30-39-years (17.7%). The hill slum sector showed only 11% of households covered by garbage collection service, the highest percentage of illiterate individuals (8.7%) and head of families with income lower than one monthly minimum wage (29.5%). Cases remained in the slum sectors. In the first epidemic year and in the inter-epidemic periods, the highest number of cases was found in the hill and flatland slum sectors; in the second and third epidemic years, in the flatland slum sector. CONCLUSIONS The economically active portion of the population was that most affected in the study area. Census tracts show spatial heterogeneity in relation to life conditions. In addition, in some tracts, there are differences in spatial and temporal distribution of the risk of occurrence of dengue fever.

Geographical Scale Effects on the Analysis of Leptospirosis Determinants

Leptospirosis displays a great diversity of routes of exposure, reservoirs, etiologic agents, and clinical symptoms. It occurs almost worldwide but its pattern of transmission varies depending where it happens. Climate change may increase the number of cases, especially in developing countries, like Brazil. Spatial analysis studies of leptospirosis have highlighted the importance of socioeconomic and environmental context. Hence, the choice of the geographical scale and unit of analysis used in the studies is pivotal, because it restricts the indicators available for the analysis and may bias the results. In this study, we evaluated which environmental and socioeconomic factors, typically used to characterize the risks of leptospirosis transmission, are more relevant at different geographical scales (i.e., regional, municipal, and local). Geographic Information Systems were used for data analysis. Correlations between leptospirosis incidence and several socioeconomic and environmental indicators were calculated at different geographical scales. At the regional scale, the strongest correlations were observed between leptospirosis incidence and the amount of people living in slums, or the percent of the area densely urbanized. At the municipal scale, there were no significant correlations. At the local level, the percent of the area prone to flooding best correlated with leptospirosis incidence.

Relevance of differentiating between residential and non-residential premises for surveillance and control of Aedes aegypti in Rio de Janeiro, Brazil

Entomological surveys on Aedes aegypti (L.) often focus on residential premises, while ignoring non-residential premises. It has been proposed that the latter should be subject to specific monitoring strategies, since they have the potential to contribute a large proportion of the overall mosquito population. In this study, we used traps for ovipositing females to compare the levels of Ae. aegypti infestation in residential and non-residential premises and assess whether there was any evidence for a spatial association of infestation between non-residential premises and the surrounding homes. This information is important for designing specific surveillance programmes for these special sites and their surroundings. This study was conducted in three neighbourhoods of the city of Rio de Janeiro, Brazil, with distinct population densities, water services, dengue histories and vegetation coverage. Ae. aegypti abundance was measured using two types of traps (standard and sticky ovitraps) installed in five non-residential premises and 80 residential premises per neighbourhood. Mosquitoes were collected in the summer (January to March) and winter (June to September) of 2007. The distribution of captures per household per week did not differ significantly between the seasons, although larger numbers of eggs and adults were obtained during the summer. Most non-residential premises were not significantly more infested than homes, despite the larger quantities of containers. There were a few exceptions, including a transportation company, two recycling centres and a boat yard. These highly infested non-residential premises were also spatially associated with highly infested homes in the vicinity. Continuous monitoring with traps may be an effective way of evaluating non-residential premises as sources of dengue vectors for nearby communities.

Spatial heterogeneity of dengue fever in local studies, City of Niterói, Southeastern Brazil

OBJETIVO: Analisar a ocorrencia espacial e temporal da dengue e sua associacao com a heterogeneidade de caracteristicas do ambiente urbano. METODOS: Foram georreferenciados 1.212 casos de dengue registrados no Sistema de Informacao de Agravos de Notificacao entre 1998 e 2006, no municipio de Niteroi, RJ, segundo setores censitarios. Os setores foram classificados em areas homogeneas para a ocorrencia da doenca: favela, estaleiro e urbano. Os casos foram agrupados em cinco periodos: dois interepidemicos 1998-2000 e 2003-2005; tres epidemicos 2001, 2002 e 2006 e analisados por meio de operacoes entre camadas em ambiente sistema de informacao geografica. Para identificacao de conglomerados com maior intensidade de casos, utilizou-se o metodo de kernel. O metodo de varredura espacial de Kulldorff foi usado para confirmacao estatistica desses clusters. RESULTADOS: Do total de casos, 57% eram do sexo feminino. As faixas etarias com maior concentracao de casos foram de 20-29 anos (20,5%) e de 30-39 anos (17,7%). O setor favela morro apresentou somente 11% dos domicilios atendidos por servico de coleta de lixo, o maior percentual de nao alfabetizados (8,7%) e de chefes de familia com rendimentos menores de 1 salario minimo (29,5%). Os casos permaneceram nos setores denominados favelas. No primeiro ano epidemico e nos periodos interepidemicos o maior numero de casos estava situado nos setores favelas morro e favela plana; no segundo e terceiro ano de epidemia, situavam-se no setor favela plana. CONCLUSOES: A parcela economicamente ativa foi a mais atingida na area de estudo. Os setores censitarios mostram heterogeneidade espacial em relacao as condicoes de vida e dentro de alguns setores, ha diferenciais na distribuicao espacial e temporal do risco de ocorrencia da dengue.OBJECTIVE To analyze the spatial and temporal occurrence of dengue fever and its association with the heterogeneity of urban environment characteristics. METHODS A total of 1,212 dengue cases, recorded in the Information System for Notifiable Diseases (Sinan) between 1998 and 2006, in the city of Niterói, Southeastern Brazil, were georeferenced according to census tracts. These tracts were classified into homogeneous areas for the occurrence of the disease: slum, shipyard and urban area. Cases were grouped into five periods--two inter-epidemic periods (1998-2000 and 2003-2005) and three epidemic periods (2001, 2002 and 2006)--and analyzed using operations between layers in a geographic information system (GIS) environment. The kernel method was used to identify clusters of cases. Kulldorffs spatial scan statistic was used to confirm these clusters statistically. RESULTS Of all cases, 57% were females. Age groups with the highest number of cases were 20-29-years (20.5%) and 30-39-years (17.7%). The hill slum sector showed only 11% of households covered by garbage collection service, the highest percentage of illiterate individuals (8.7%) and head of families with income lower than one monthly minimum wage (29.5%). Cases remained in the slum sectors. In the first epidemic year and in the inter-epidemic periods, the highest number of cases was found in the hill and flatland slum sectors; in the second and third epidemic years, in the flatland slum sector. CONCLUSIONS The economically active portion of the population was that most affected in the study area. Census tracts show spatial heterogeneity in relation to life conditions. In addition, in some tracts, there are differences in spatial and temporal distribution of the risk of occurrence of dengue fever.

Spatial distribution and socioeconomic context of tuberculosis in Rio de Janeiro, Brazil

OBJECTIVE To analyze the spatial distribution of risk for tuberculosis and its socioeconomic determinants in the city of Rio de Janeiro, Brazil. METHODS An ecological study on the association between the mean incidence rate of tuberculosis from 2004 to 2006 and socioeconomic indicators of the Censo Demográfico (Demographic Census) of 2000. The unit of analysis was the home district registered in the Sistema de Informação de Agravos de Notificação (Notifiable Diseases Information System) of Rio de Janeiro, Southeastern Brazil. The rates were standardized by sex and age group, and smoothed by the empirical Bayes method. Spatial autocorrelation was evaluated by Moran’s I. Multiple linear regression models were studied and the appropriateness of incorporating the spatial component in modeling was evaluated. RESULTS We observed a higher risk of the disease in some neighborhoods of the port and north regions, as well as a high incidence in the slums of Rocinha and Vidigal, in the south region, and Cidade de Deus, in the west. The final model identified a positive association for the variables: percentage of permanent private households in which the head of the house earns three to five minimum wages; percentage of individual residents in the neighborhood; and percentage of people living in homes with more than two people per bedroom. CONCLUSIONS The spatial analysis identified areas of risk of tuberculosis incidence in the neighborhoods of the city of Rio de Janeiro and also found spatial dependence for the incidence of tuberculosis and some socioeconomic variables. However, the inclusion of the space component in the final model was not required during the modeling process.