How to overcome the stagnation of the first dose vaccine coverage curve against coronavirus disease 2019 in Brazil?

BACKGROUND

A large percentage of the population has not yet started vaccination, for which the increase in coverage is almost null.

METHODS

We used segmented regression analysis to estimate trends in the first dose coverage curve.

RESULTS

There has been a slowdown in the application of the first doses in Brazil since epidemiological week 36 (average percent change [APC] 0.83%, 95% confidence interval [CI] 0.75-0.91%), with a trend close to stagnation.

CONCLUSIONS

It is important to develop strategies to increase access to vaccination posts. Furthermore, it is recommended to expand vaccination to children, thereby increasing the eligible population.

A Spatial Analysis of the Spread of Hyperendemic Sporotrichosis in the State of Rio de Janeiro, Brazil

Sporotrichosis is a subacute/chronic subcutaneous mycosis. Since the late 1990s, there has been a hyperendemic zoonotic transmission in the state of Rio de Janeiro, involving Sporothrix brasiliensis, the most virulent causative species, and a “belt” was described along the limits between the capital and its outskirts (“Baixada Fluminense”). This study analyzes the distribution of sporotrichosis using secondary data from the Notifiable Diseases Information System (Sinan) of the Rio de Janeiro State Health Department (SES/RJ) from 2011 to 2015 and from the INI Electronic Patient Record System (Sipec) from 2008 to 2015. Cases diagnosed since the onset of the hyperendemic exceed all previously reported case series of the disease and there is a progressive expansion in the state of Rio de Janeiro. The study suggests the spread of the mycosis to all regions of the state and the expansion of the previously described “belt”, despite public health measures and changes in its profile over the years, with great social impact.

Ecological and environmental factors affecting transmission of sylvatic yellow fever in the 2017-2019 outbreak in the Atlantic Forest, Brazil

BACKGROUND

Yellow fever virus (YFV) is an arbovirus that, despite the existence of a safe and effective vaccine, continues to cause outbreaks of varying dimensions in the Americas and Africa. Between 2017 and 2019, Brazil registered un unprecedented sylvatic YFV outbreak whose severity was the result of its spread into zones of the Atlantic Forest with no signals of viral circulation for nearly 80 years.

METHODS

To investigate the influence of climatic, environmental, and ecological factors governing the dispersion and force of infection of YFV in a naïve area such as the landscape mosaic of Rio de Janeiro (RJ), we combined the analyses of a large set of data including entomological sampling performed before and during the 2017-2019 outbreak, with the geolocation of human and nonhuman primates (NHP) and mosquito infections.

RESULTS

A greater abundance of Haemagogus mosquitoes combined with lower richness and diversity of mosquito fauna increased the probability of finding a YFV-infected mosquito. Furthermore, the analysis of functional traits showed that certain functional groups, composed mainly of Aedini mosquitoes which includes Aedes and Haemagogus mosquitoes, are also more representative in areas where infected mosquitoes were found. Human and NHP infections were more common in two types of landscapes: large and continuous forest, capable of harboring many YFV hosts, and patches of small forest fragments, where environmental imbalance can lead to a greater density of the primary vectors and high human exposure. In both, we show that most human infections (~ 62%) occurred within an 11-km radius of the finding of an infected NHP, which is in line with the flight range of the primary vectors.

CONCLUSIONS

Together, our data suggest that entomological data and landscape composition analyses may help to predict areas permissive to yellow fever outbreaks, allowing protective measures to be taken to avoid human cases.

Mortality of motorcyclists due to traffic injuries in Brasil: a population-based study in Brazilian capitals

OBJECTIVE

To analyze the mortality trend of young men who were victims of traffic injuries involving motorcycles in all Brazilian capitals from 2001 to 2015.

METHODS

A time-series study on all deaths of men aged 20-39 years old due to traffic injuries involving motorcycles in all 27 Brazilian capitals. We used the joinpoint regression model for temporal analysis and calculated the Annual Percent Change (APC) and Average Annual Percent Change (AAPC) to verify the mortality trends.

RESULTS

A total of 12,058 deaths of young men were recorded in the Brazilian capitals during the period studied. The highest mortality rates were observed in Boa Vista/Roraima (34.0/100,000 population) and Palmas/Tocantins (29.80/100,000). Twelve of the 27 capitals showed an increasing trend in mortality, with the highest percentage increase being observed in Salvador (APC: 29.0%) and São Paulo (APC: 13.1%). None of the capitals showed a decline in the trend of mortality.

CONCLUSIONS

Overall, the mortality of young men from traffic injuries involving motorcycles shows an increasing trend in 12 of the 27 capitals, which represents a public health problem that requires the implementation of more effective public policies.

Mortality due to acquired immunodeficiency syndrome and associated social factors: a spatial analysis

OBJECTIVE

To analyze the spatial pattern of AIDS mortality and social factors associated with its occurrence.

METHODS

An ecological study that considered 955 AIDS deaths of residents in Piauí, reported in the Mortality Information System (MIS) from 2007 to 2015. Non-spatial and spatial regression models were used to identify social determinants of AIDS mortality, with a significance of 5%.

RESULTS

The predictors of AIDS mortality were illiteracy rate in males (p = 0.020), proportion of households with water supply (p = 0.015), percentage of people in households with inadequate walls (p = 0.022), percentage of people in households vulnerable to poverty and in whom no one has completed primary education (p = 0.000) and percentage of people in households vulnerable to poverty and dependent on the elderly (p = 0.009).

CONCLUSION

Social indicators related to education, job and income generation and housing were associated with AIDS mortality.

Modelagem espacial da hanseníase no estado da Bahia, Brasil, (2001-2015) e determinantes sociais da saúde

Resumo O trabalho analisa a distribuição espacial da hanseníase na Bahia e os determinantes sociais relacionados. Estudo ecológico com dados de hanseníase do período 2001-2015. Três indicadores epidemiológicos foram selecionados: coeficiente de detecção na população geral e em menores de 15 anos e a taxa de casos novos com grau II de incapacidade. Os indicadores foram suavizados pelo Modelo Bayesiano Empírico Local e aplicou-se estatística de Moran Global e Local. As variáveis independentes foram selecionadas a partir do Censo IBGE-2010. Regressões multivariadas foram empregadas, seguidas de regressão espacial. Observou-se distribuição heterogênea no estado, com concentração no eixo norte-oeste e região sul. Para o coeficiente de detecção geral, cinco variáveis compuseram o modelo: densidade demográfica, proporção da população urbana, renda per capita, proporção de extremamente pobres e domicílios com mais de três pessoas por dormitório. A proporção de analfabetismo compôs o modelo final para a taxa de grau II de incapacidade física. Não foram identificados determinantes da ocorrência da doença em menores de 15 anos. A modelagem utilizada contribuiu para demonstrar a heterogeneidade espacial e os determinantes sociais da doença na Bahia, colocando em evidência a complexidade do problema.

Is it time to talk about the end of social distancing? A joinpoint analysis of COVID-19 time series in Brazilian capitals

INTRODUCTION:

Monitoring coronavirus disease (COVID-19)-related infections and deaths in Brazil is controversial, with increasing pressure to ease social distance measures. However, no evidence of a sustained, widespread fall in cases exists.

METHODS

We used segmented (joinpoint) regression analysis to describe the behavior of COVID-19 infections in Brazilian capital cities.

RESULTS

All capitals showed an exponential or a near-exponential increase in cases through May. A decline in reported cases was subsequently noted in 20 cities but was only significant for 8 (29.6%) and was followed in two by a renewed increase.

CONCLUSIONS

Caution is warranted when considering the relaxation of restrictions.

INFLUENCE OF THE SOCIAL DETERMINANTS ON THE INCIDENCE OF AIDS IN PIAUÍ: AN ECOLOGICAL STUDY

ABSTRACT Objective: to identify the social factors that determine the incidence of aids in the Piauí territory. Method: an ecological study that uses geoprocessing techniques in which 2,908 aids cases of individuals residing in Piauí were considered, notified to the Notifiable Disease Information System (Sistema de Informações de Agravos de Notificação, SINAN), from 2007 to 2015. Gross and Bayesian incidence rates were calculated using the population of the central year (2011), multiplied by 100,000 inhabitants, with Bayesian statistics used to identify spatial clusters. The non-spatial Ordinary Least Squares Estimation (OLS) and spatial Geographically Weighted Regression (GWR) regression models were used to identify the social determinants of the incidence of aids in the state, with 5% of significance. Results: the highest rates of the disease are concentrated in cities near the capital Teresina, with a Bayesian incidence of over 11.27 cases/100,000 inhabitants. The predictor variables of the incidence of ADIS in Piauí cities were the following: the percentage of individuals in houses with inadequate walls (p=0.0139), the mean number of residents per household (p=0.0309), and the percentage of individuals in households vulnerable to poverty and in which no one has completed elementary school (p=0.0051). Conclusion: according to GWR, the social factors that influence the incidence of aids in the cities of Piauí are the percentage of individuals in houses with inadequate walls, the mean number of residents per household, and the percentage of individuals in houses vulnerable to poverty and in which no one has completed elementary school. Given the above, interventions on the health social determinants of a structural nature should be established as effective methods for the prevention of HIV/ aids.

Adesão às medidas de restrição de contato físico e disseminação da COVID-19 no Brasil

Resumo Objetivo: Analisar a adesão da população às medidas de restrição de contato físico e disseminação da COVID-19 no Brasil. Métodos: Inquérito de saúde, realizado pela internet, com amostragem em cadeia, no período de 24 de abril a 24 de maio de 2020. A intensidade da adesão à restrição de contato físico foi analisada segundo características sociodemográficas, utilizando-se modelos de regressão logística para investigar associações com ‘Nenhuma/pouca adesão’. Resultados: Dos 45.161 participantes, 74,2% (73,8-74,6%) relataram intensa adesão às medidas. O grupo que não aderiu às medidas foi composto homens (31,7%), com idade de 30 a 49 anos (36,4%), baixa escolaridade (33,0%), trabalhando durante a pandemia (81,3%), residentes nas regiões Norte (28,1%) e Centro-Oeste (28,5%) do país. Houve importante redução das taxas de crescimento diário, de 45,4 para 5,0%. Conclusão: Grande parte da população brasileira aderiu às medidas de restrição de contato físico, o que, possivelmente, contribuiu para reduzir a disseminação da COVID-19.

Spatial spread of malaria and economic frontier expansion in the Brazilian Amazon

The temporal and spatial evolution of malaria was described for the postfrontier phase of the Brazilian Amazon in 2003–2013. The current ecological study aimed to understand the relationship between spatial population mobility and the distribution of malaria cases. The study identified epidemiologically relevant areas using regional statistical modeling and spatial analyses that considered differential infections and types of work activities. Annual parasite incidence (API) in the region was highest in hotspots along the Amazon River and in the south and west settlement zone of Hiléia, with concentrations in environmental protection areas and açaí and Brazil nut extraction areas. The dispersal force decreased in the Central Amazon due to rapid urbanization and improved socioeconomic conditions for workers in consolidated settlement areas. The study characterized the spatial patterns of disease transmission according to the economic activity and regionalization of geographic areas, confirming that the incidence of infection by work activity and labor flow is linked to extractive activities and agricultural settlements.

Trends in tuberculosis mortality in Brazil (1990-2015): joinpoint analysis

The objective of this study was to analyze trends in the tuberculosis mortality rate in Brazil (1990-2015) in an ecological time-series analysis. The indicators were obtained from the Brazilian National Ministry of Health. A joinpoint regression model was applied for the temporal analysis, with a level of significance of 5%. During the period in question, there was a trend toward a reduction in mortality in the country as a whole (p < 0.001) and in each of its five regions. The states with the highest tuberculosis mortality rates were Rio de Janeiro (7.0/100,000 population) and Pernambuco (5.0/100,000 population). Eleven states and the Federal District of Brasília showed downward trends. Only the state of Alagoas showed a significant increase (p < 0.001). The temporal behavior observed indicates that tuberculosis continues to be a major public health problem in Brazil.

Spatial modeling of leprosy in the state of Bahia and its social determinants: a study of health inequities

BACKGROUND

Leprosy is a neglected disease caused by Mycobacterium leprae. Brazil has the second largest number of cases in the world.

OBJECTIVES

To analyze the spatial distribution of leprosy in the state of BAHIA, Brazil, and the association between his occurrence and the synthetic indicators of municipal socioeconomic performance, social vulnerability and income inequality.

METHODS

An ecological study with secondary data obtained from the National System of Notifiable Diseases. Dependent variables: coefficient of detection in the general population and in the population under 15 years old and the rate of grade II of physical disability. Independent variables: Synthetic indicators of socioeconomic performance, social vulnerability and income inequality.

RESULTS

The highest coefficients of detection of new cases in the general population and in children under 15 years old are concentrated in the north-west axis and in the southern region of the state. On the other hand, the highest rates of degree II of physical incapacity are concentrated in the north, northeast and south regions. Only the Index of Social and Economic Performance(IPESE)-Economy and Finance composed the final regression model of the general detection coefficients and in children under 15 years old. The municipalities with the highest indexes had the highest detection coefficients, reflecting the capacity to diagnose new cases.

STUDY LIMITATIONS

The use of synthetic indicators is a limitation of the study.

CONCLUSIONS

Leprosy presents a heterogeneous spatial pattern in the state of BAHIA, and the IPESE-Economics and Finance indicator is the only one with explanatory potential of the disease.

Analysis of the spatial distribution of dengue cases in the city of Rio de Janeiro, 2011 and 2012

OBJECTIVE

Analyze the spatial distribution of classical dengue and severe dengue cases in the city of Rio de Janeiro.

METHODS

Exploratory study, considering cases of classical dengue and severe dengue with laboratory confirmation of the infection in the city of Rio de Janeiro during the years 2011/2012. The georeferencing technique was applied for the cases notified in the Notification Increase Information System in the period of 2011 and 2012. For this process, the fields "street" and "number" were used. The ArcGis10 program's Geocoding tool's automatic process was performed. The spatial analysis was done through the kernel density estimator.

RESULTS

Kernel density pointed out hotspots for classic dengue that did not coincide geographically with severe dengue and were in or near favelas. The kernel ratio did not show a notable change in the spatial distribution pattern observed in the kernel density analysis. The georeferencing process showed a loss of 41% of classic dengue registries and 17% of severe dengue registries due to the address in the Notification Increase Information System form.

CONCLUSIONS

The hotspots near the favelas suggest that the social vulnerability of these localities can be an influencing factor for the occurrence of this aggravation since there is a deficiency of the supply and access to essential goods and services for the population. To reduce this vulnerability, interventions must be related to macroeconomic policies.

OBJETIVO

Analisar a distribuição espacial dos casos de dengue clássico e dengue grave no município do Rio de Janeiro.

MÉTODOS

Estudo exploratório, considerando casos de dengue clássico e de dengue grave com comprovação laboratorial da infecção, ocorridos no município do Rio de Janeiro nos anos de 2011/2012. Foi aplicada a técnica de georreferenciamento dos casos notificados no Sistema de Informação de Agravos de Notificação, no período de 2011 e 2012. Para esse processo, utilizaram-se os campos "logradouro" e "número". Foi realizado o processo automático da ferramenta Geocoding do programa ArcGis10. A análise espacial foi feita a partir do estimador de densidade Kernel.

RESULTADOS

A densidade de Kernel apontou áreas quentes para dengue clássico não coincidente geograficamente a dengue grave, estando localizadas dentro ou próximas de favelas. O cálculo da razão de Kernel não apresentou modificação significativa no padrão de distribuição espacial observados na análise da densidade de Kernel. O processo de georreferenciamento mostrou perda de 41% dos registros de dengue clássico e 17% de dengue grave devido ao endereçamento da ficha do Sistema de Informação de Agravos de Notificação.

CONCLUSÕES

As áreas quentes próximas às favelas sugerem que a vulnerabilidade social existente nessas localidades pode ser um fator de influência para a ocorrência desse agravo, uma vez que há deficiência da oferta e acesso a bens e serviços essenciais para a população. Para diminuir essa vulnerabilidade, as intervenções devem estar relacionadas a políticas macroeconômicas.

Spatial-temporal diffusion of dengue in the municipality of Rio de Janeiro, Brazil, 2000-2013

The city of Rio de Janeiro, Brazil, shows high potential receptiveness to the introduction, dissemination, and persistence of dengue transmission. The pattern of territorial occupation in the municipality produced a heterogeneous and diverse mosaic, with differential vector distribution between and within neighborhoods, producing distinct epidemics on this scale of observation. The study seeks to identify these epidemics and the pattern of spatial and temporal diffusion of dengue transmission. A model was used for the identification of epidemics, considering the epidemic peak years and months, spatial distribution, and permanence of epidemics from January 2000 to December 2013. A total of 495 epidemic peaks were counted, and the time scale showed the highest occurrence in the months of March, April, and February, respectively. Some neighborhoods appear to present persistent dengue incidence, and the pattern of diffusion allows identifying key trajectories and timely months for intervention.

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.

Mapping of the environmental contamination of Toxoplasma gondii by georeferencing isolates from chickens in an endemic area in Southeast Rio de Janeiro State, Brazil

The environmental contamination of Toxoplasma gondii in an endemic area in Brazil was mapped by georeferencing isolates from chickens in farms in the Southeast of the state of Rio de Janeiro. Tissue samples obtained from 153 adult chickens were analyzed by the mouse bioassay for T. gondii infection. These animals were reared free-range on 51 farms in the municipalities of Rio Bonito and Maricá. The ArcGIS kernel density estimator based on the frequency of T. gondii-positive chickens was used to map the environmental contamination with this parasite. A questionnaire was applied to obtain data on the presence and management of cats and the type of water consumed. Of the farms studied, 64.7% were found to be located in areas of low to medium presence of T. gondii, 27.5% in areas with a high or very high contamination level and 7.8% in non-contaminated areas. Additionally, 70.6% kept cats, 66.7% were near water sources and 45.0% were in or near dense vegetation. Humans used untreated water for drinking on 41.2% of the farms, while all animals were given untreated water. The intensity of environmental T. gondii contamination was significantly higher on farms situated at a distance &gt;500 m from water sources (P=0.007) and near (≤500 m) dense vegetation (P=0.003). Taken together, the results indicate a high probability of T. gondii infection of humans and animals living on the farms studied. The kernel density estimator obtained based on the frequency of chickens testing positive for T. gondii in the mouse bioassay was useful to map environmental contamination with this parasite.

Avaliação do dado sobre endereço no Sistema de Informação de Agravos de Notificação utilizando georreferenciamento em nível local de casos de tuberculose por dois métodos no município do Rio de Janeiro

O presente trabalho objetivou avaliar a qualidade dos dados referentes ao endereço dos casos notificados de tuberculose (TB) ao Sistema de Informação de Agravos de Notificação (SINAN), de 2005 a 2008, no município do Rio de Janeiro. Criou-se um indicador a partir da razão entre a taxa de incidência da TB calculada a partir do bairro de moradia declarado pelo paciente e a taxa de incidência do bairro obtida após o georreferenciamento do endereço do mesmo indivíduo, com o intuito de medir possíveis impactos que inconsistências no endereço podem causar nos cálculos de indicadores da doença por bairro. Foram utilizadas duas técnicas de georreferenciamento de dados a partir do endereço de residência. Foi realizada uma correção no campo endereço que modificou 27% dos registros. Houve uma diferença no resultado do georreferenciamento entre os dois métodos de 64 e 69%. Com o processo manual, chegou-se a 89% de localização. A partir do indicador criado, nota-se que apenas 28% dos bairros apresentaram um valor entre 0,85 e 1,15, considerado como razoável. O processo de localização pode ser mais rápido e eficaz após maior conscientização e treinamento dos profissionais responsáveis e utilização de algum cadastro oficial de logradouros. As diferenças apresentadas no indicador I podem auxiliar na tomada de decisões mais acertadas.

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.

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

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. Kulldorff's 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 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 household's 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.

Dengue is a major public health problem in many tropical regions of the world, including Brazil, where Aedes aegypti is the main vector. We present a household study that combines data on dengue fever seroprevalence, recent dengue infection, and vector density, in three neighborhoods of Rio de Janeiro, Brazil, during its most devastating dengue epidemic to date. This integrated entomological–serological survey showed evidence of silent transmission even during a severe epidemic. Also, past exposure to dengue virus was highly associated with age and living in areas of high movement of individuals and social/commercial activity. No association was observed between household infestation index and risk of dengue infection in these areas. Our findings are discussed in the light of current theories regarding transmission thresholds and relative role of mosquitoes and humans as vectors of dengue viruses.