Autochthonous Dengue Cases Research Articles

A cluster of autochthonous dengue transmission in the Paris region - detection, epidemiology and control measures, France, October 2023.

A cluster of three confirmed autochthonous dengue cases was detected in October 2023 in the Val-de-Marne department neighbouring Paris, France. This marks the northernmost transmission of dengue in Europe reported to date. The epidemiological and microbiological investigations and the vector control measures are described. This event confirms the need for early case detection and response to contain dengue in Europe, especially given the 2024 Summer Olympic and Paralympic Games, when millions of visitors will visit the Greater Paris area.

Autochthonous Dengue Outbreak, Paris Region, France, September-October 2023.

We describe clinical and laboratory findings of 3 autochthonous cases of dengue in the Paris Region, France, during September-October 2023. Increasing trends in cases, global warming, and growth of international travel mean that such infections likely will increase during warm seasons in France, requiring stronger arbovirus surveillance networks.

Species-specific climate Suitable Conditions Index and dengue transmission in Guangdong, China

BackgroundOptimal climatic conditions for dengue vector mosquito species may play a significant role in dengue transmission. We previously developed a species-specific Suitable Conditions Index (SCI) for Aedes aegypti and Aedes albopictus, respectively. These SCIs rank geographic locations based on their climatic suitability for each of these two dengue vector species and theoretically define parameters for transmission probability. The aim of the study presented here was to use these SCIs together with socio-environmental factors to predict dengue outbreaks in the real world.MethodsA negative binomial regression model was used to assess the relationship between vector species-specific SCI and autochthonous dengue cases after accounting for potential confounders in Guangdong, China. The potential interactive effect between the SCI for Ae. albopictus and the SCI for Ae. aegypti on dengue transmission was assessed.ResultsThe SCI for Ae. aegypti was found to be positively associated with autochthonous dengue transmission (incidence rate ratio: 1.06, 95% confidence interval: 1.03, 1.09). A significant interaction effect between the SCI of Ae. albopictus and the SCI of Ae. aegypti was found, with the SCI of Ae. albopictus significantly reducing the effect of the SCI of Ae. aegypti on autochthonous dengue cases. The difference in SCIs had a positive effect on autochthonous dengue cases.ConclusionsOur results suggest that dengue fever is more transmittable in regions with warmer weather conditions (high SCI for Ae. aegypti). The SCI of Ae. aegypti would be a useful index to predict dengue transmission in Guangdong, China, even in dengue epidemic regions with Ae. albopictus present. The results also support the benefit of the SCI for evaluating dengue outbreak risk in terms of vector sympatry and interactions in the absence of entomology data in future research.Graphical

Autochthonous dengue outbreak in Italy 2020: clinical, virological and entomological findings.

BackgroundIn August 2020, in the context of COVID-19 pandemics, an autochthonous dengue outbreak was identified for the first time in Italy.MethodsFollowing the reporting of the index case of autochthonous dengue, epidemiological investigation, vector control and substances of human origin safety measures were immediately activated, according to the national arbovirus surveillance plan. Dengue cases were followed-up with weekly visits and laboratory tests until recovery and clearance of viral RNA from blood.ResultsThe primary dengue case was identified in a young woman, who developed fever after returning from Indonesia to northern Italy, on 27 July 2020. She spent the mandatory quarantine for COVID-19 at home with relatives, six of whom developed dengue within two weeks. Epidemiological investigation identified further five autochthonous dengue cases among people who lived or stayed near the residence of the primary case. The last case of the outbreak developed fever on 29 September 2020. Dengue cases had a mild febrile illness, except one with persistent asthenia and myalgia. DENV-1 RNA was detected in blood and/or urine in all autochthonous cases, up to 35 days after fever onset. All cases developed IgM and IgG antibodies which cross-reacted with West Nile virus (WNV) and other flaviviruses. Sequencing of the full viral genome from blood samples showed over 99% nucleotide identity with DENV-1 strains isolated in China in 2014–2015; phylogenetic analysis classified the virus within Genotype I. Entomological site inspection identified a high density of Aedes albopictus mosquitoes, which conceivably sustained local DENV-1 transmission. Aedes koreicus mosquitoes were also collected in the site.ConclusionsAreas in Europe with high density of Aedes mosquitoes should be considered at risk for dengue transmission. The presence of endemic flaviviruses, such as WNV, might pose problems in the laboratory diagnosis.

Virome Diversity among Mosquito Populations in a Sub-Urban Region of Marseille, France.

Some mosquito species have significant public health importance given their ability to transmit major diseases to humans and animals, making them the deadliest animals in the world. Among these, the Aedes (Ae.) genus is a vector of several viruses such as Dengue, Chikungunya, and Zika viruses that can cause serious pathologies in humans. Since 2004, Ae. albopictus has been encountered in the South of France, and autochthonous cases of Dengue, Chikungunya, and Zika diseases have recently been reported, further highlighting the need for a comprehensive survey of the mosquitoes and their associated viruses in this area. Using high throughput sequencing (HTS) techniques, we report an analysis of the DNA and RNA viral communities of three mosquito species Ae. albopictus, Culex (Cx.) pipiens, and Culiseta (Cs.) longiareolata vectors of human infectious diseases in a small sub-urban city in the South of France. Results revealed the presence of a significant diversity of viruses known to infect bacteria, plants, insects, and mammals. Several novel viruses were detected, including novel members of the Rhabdoviridae, Totiviridae, Iflaviviridae, Circoviridae, and Sobemoviridae families. No sequence related to major zoonotic viruses transmitted by mosquitoes was detected. The use of HTS on arthropod vector populations is a promising strategy for monitoring the emergence and circulation of zoonoses and epizooties. This study is a contribution to the knowledge of the mosquito microbiome.

Emerging and Neglected Viruses of Zoonotic Importance in Croatia.

Several arboviruses have emerged in Croatia in recent years. Tick-borne encephalitis is endemic in continental counties; however, new natural micro-foci have been detected. Two autochthonous dengue cases were reported in 2010. West Nile virus emerged in 2012, followed by emergence of Usutu virus in 2013. Although high seroprevalence rates of Toscana virus have been detected among residents of Croatian littoral, the virus remains neglected, with only a few clinical cases of neuroinvasive infections reported. Lymphocytic choriomeningitis virus is a neglected neuroinvasive rodent-borne virus. So far, there are no reports on human clinical cases; however, the seroprevalence studies indicate the virus presence in the Croatian mainland. Puumala and Dobrava hantaviruses are widely distributing rodent-borne viruses with sporadic and epidemic occurrence. Hepatitis E virus is an emerging food-borne virus in Croatia. After the emergence in 2012, cases were regularly recorded. Seropositivity varies greatly by region and population group. Rotaviruses represent a significant healthcare burden since rotavirus vaccination is not included in the Croatian national immunization program. Additionally, rotaviruses are widely distributed in the Croatian ecosystem. A novel coronavirus, SARS-CoV-2, emerged in February 2020 and spread rapidly throughout the country. This review focuses on emerging and neglected viruses of zoonotic importance detected in Croatia.

Molecular Characterization of Mosquito Diversity in the Balearic Islands.

Several outbreaks of mosquito-borne diseases have taken place in Europe in recent years. In Spain, both active and passive surveillance have demonstrated that dengue and West Nile viruses are currently circulating, and seven autochthonous dengue cases have been reported in the last 2 yr. The effectiveness of vector control programs largely depends on the accuracy of the taxonomic identification of the species. However, in Spain, identification almost completely relies on the use of morphological keys to characterize the mosquito fauna. This study investigates the congruence between molecular and morphological species boundaries in 13 Spanish mosquito taxa. The Cytochrome c oxidase subunit I (COI) gene region was sequenced from 60 adult specimens collected in Mallorca, plus several representatives from other Spanish regions for comparative purposes. Phylogenetic relationships were established using Bayesian and maximum-likelihood approaches. Using three species delimitation algorithms (ABGD, mPTP, and GMYC), we found strong evidence for cryptic speciation within Anopheles algeriensis Theobald, a widespread mosquito in the Mediterranean basin. We also delimited the Mallorcan rock pool mosquito Aedes mariae (Sergent & Sergent), from mainland European populations. Finally, we found difficulties in the use of wing characters in species keys to distinguish Culiseta annulata (Schrk) from Culiseta subochrea (Edwards). Given that these species are vectors of pathogens of medical relevance and have veterinary importance, their accurate taxonomic identification is essential in European vector surveillance programs.

Autochthonous dengue in two Dutch tourists visiting Département Var, southern France, July 2020.

We report dengue virus (DENV) infection in two Dutch tourists who visited Département Var, southern France, in July and August 2020. As some autochthonous dengue cases have occurred in Europe in recent years, awareness among physicians and public health experts about possible intermittent presence of DENV in southern Europe is important to minimise delay in diagnosis and treatment. Quick diagnosis can lead to timely action to contain the spread of vector-borne diseases and minimise transmission.

Descriptive profile of the occurrence of arboviruses in Governador Valadares, Minas Gerais, Brazil

Objective: The objectives of this study were to analyse the clinical-demographic profile of arbovirus cases in Governador Valadares, Minas Gerais, Brazil, between 2015 and 2016, and the incompleteness of notifications. Methods: A descriptive and cross-sectional study of arboviruses was performed using secondary data. All reported autochthonous probable cases (confirmed and suspected) of Dengue, Chikungunya and Zika were included. Results: In total, 4,207 cases (dengue), 3,310 (zika) and 130 (chikungunya) were reported; the annual incidence rates (per 100,000 inhabitants) were 752.1 cases (dengue), 24.3 (chikungunya) and 591.8 (zika). February was the month with the highest notification for 3 arboviruses and female individuals were the most frequently affected. The most frequent age range for dengue was between 21 and 30 years old (20.3%), for chikungunya was over 50 years old (23.5%) and for zika was under 10 years old (28.6%). The most incident symptoms in dengue were fever (3.2%), headache (2.9%) and myalgia (2.6%), in chikungunya were arthralgia (46.6%), exanthema (37.5%) and myalgia (29.4%); for zika, the symptoms weren’t reported in the notification form. Very poor or poor completeness were verified in 77.4% (dengue), 34.6% (chikungunya), 22.2% (zika). Conclusions: The clinical-demographic profile of arboviruses in Governador Valadares is represented by women, aged between 21 and 40 years old, with complaints of fever, headache, myalgia and, particularly in chikungunya, arthralgia. The high percentage of unfilled fields in notification forms for 3 arboviruses is a serious limitation for public health actions against them.

Invasion of Tropical Montane Cities by Aedes aegypti and Aedes albopictus (Diptera: Culicidae) Depends on Continuous Warm Winters and Suitable Urban Biotopes.

We provide the first evidence of a recent invasion of Aedes aegypti (Linnaeus in Hasselquist, 1762) and Aedes albopictus (Skuse 1894), followed by dengue virus, in tropical montane cities in south-eastern Brazil, Mariana, and Ouro Preto, at mid and high altitudes, respectively. Long-term temperature variation, dengue public data, and sampling of immature and adult mosquitoes (ovitraps and mosquitraps) in contrasting habitats were used to explain the distribution of Aedes in what in these two cities. From 1961 to 2014, the annual temperature increased significantly due to increases in winter temperatures. In the 1990s/2000s, the winter temperature was 1.3°C warmer than in the 1960s, when it varied from 21.2 to 18.9°C. After 2007, the winter temperatures increased and ranged from 21.6 to 21.3°C. The first autochthonous dengue cases in Mariana and Ouro Preto were in 2007, followed by few occurrences until in 2012, when the mean numbers increased three-fold, and peak at 2013. The continuous 'warmer winter' may have trigged the Aedes invasion. Aedes species benefited from higher winter temperatures, which was an important driver of their invasion of the state of Minas Gerais in the 1980s and, more recently, in the remaining montane urban habitats in this region. In both 2009 and 2011, we found more Aedes in Mariana than Ouro Preto, and more Ae. albopictus in green areas and Ae. aegypti in houses, the expected pattern for well-established populations.

IgG Antibody Responses to the Aedes albopictus 34k2 Salivary Protein as Novel Candidate Marker of Human Exposure to the Tiger Mosquito.

Mosquitoes of the Aedes genus transmit arboviruses of great importance to human health as dengue, chikungunya, Zika and yellow fever. The tiger mosquito Aedes albopictus can play an important role as arboviral vector, especially when Aedes aegypti is absent or present at low levels. Remarkably, the rapid worldwide spreading of the tiger mosquito is expanding the risk of arboviral transmission also to temperate areas, and the autochthonous cases of chikungunya, dengue and Zika in Europe emphasize the need for improved monitoring and control. Proteomic and transcriptomic studies on blood feeding arthropod salivary proteins paved the way toward the exploitation of genus-specific mosquito salivary proteins for the development of novel tools to evaluate human exposure to mosquito bites. We previously found that the culicine-specific 34k2 salivary protein from Ae. albopictus (al34k2) evokes specific IgG responses in experimentally exposed mice, and provided preliminary evidence of its immunogenicity to humans. In this study we measured IgG responses to al34k2 and to Ae. albopictus salivary gland protein extracts (SGE) in individuals naturally exposed to the tiger mosquito. Sera were collected in two areas of Northeast Italy (Padova and Belluno) during two different time periods: at the end of the low- and shortly after the high-density mosquito seasons. Anti-SGE and anti-al34k2 IgG levels increased after the summer period of exposure to mosquito bites and were higher in Padova as compared to Belluno. An age-dependent decrease of anti-saliva IgG responses was found especially in Padova, an area with at least 25 years history of Ae. albopictus colonization. Moreover, a weak correlation between anti-saliva IgG levels and individual perception of mosquito bites by study participants was found. Finally, determination of anti-al34k2 IgG1 and IgG4 levels indicated a large predominance of IgG1 antibodies. Overall, this study provides a convincing indication that antibody responses to al34k2 may be regarded as a reliable candidate marker to detect temporal and/or spatial variation of human exposure to Ae. albopictus; a serological tool of this kind may prove useful both for epidemiological studies and to estimate the effectiveness of anti-vectorial measures.

Infections virales transmises par les moustiques

Mosquitoes are mainly responsible for the transmission of arboviruses (Arthropod-borne viruses) characterized by their transmission by arthropod vectors. Among the mosquitoes transmitting arboviruses, Aedes and Culex genera play a major role. Aedes (Stegomyia) aegypti, found in tropical and subtropical regions, is the main vector for dengue, chikungunya and Zika viruses and is responsible for large-scale epidemics. Aedes (Stegomyia) albopictus is a species native to Southeast Asia that has spread to many temperate countries including metropolitan France. This virus is responsible for the autochthonous cases of dengue, chikungunya and Zika regularly observed in France for about ten years. Culex modestus and Culex pipiens are vectors for the West-Nile virus whose incidence is increasing in the south of France. Mosquitoes present in Metropolitan France may also be vectors for Usutu and Tahyna viruses. The implantation of new species of mosquito vectors or the importation of viruses that can be transmitted by mosquitoes present in metropolitan France are hypotheses to be considered.

Consolidation of Aedes albopictus Surveillance Program in the Autonomous Community of the Region of Murcia, Spain.

Background: Due to the Spanish legal framework, the national program for vector-borne diseases results from the agreement between national and regional governments, and it is the basis for the development of the regional programs, which should include the regional entomological surveillance program. Aedes albopictus was recorded for the first time in the Region of Murcia, in 2011. It gave rise to a new epidemiological scenario due to the presence of a competent vector of several arboviruses, which resulted in autochthonous cases of dengue in 2018. Methods: 40 out of 45 municipalities participated in the regional entomological surveillance program, and 266 sampling points were established, with two ovitraps at each site as pseudo-replications. The study period was from April 16th to November 26th, with bi-weekly sample collections: 16 regional samplings were carried out. Results: Regional participation was high, and data loss was low (1.26%). Ae. albopictus was detected in 4.9% of samples and 89.4% of points, located in 39 of the 40 municipalities. The intensity of the presence of Ae. albopictus was estimated by a positivity index, that is, the percentage of positive samples over time. The vector phenology was obtained at a regional level, using the number of eggs as estimation of population density and the positivity values of points and municipalities. Every two weeks, real-time results were provided to the municipalities, which could use them as a vector management tool. Conclusion: The regional entomological surveillance program for Ae. albopictus in the Region of Murcia was consolidated in 2019, with standardized and comparable methods. Almost all the municipalities of the region have observed the presence of Ae. albopictus, although intensity and spatial and temporal cover vary among them.

A series of the studies on countermeasure for arthropod-borne infectious diseases in Japan —Focus on highly pathogenic avian influenza and dengue outbreaks in Japan—

We have faced a number of outbreaks of arthropod-borne infectious diseases in Japan and aimed to address each case appropriately. Here, I introduce two arthropod-borne infectious diseases caused by flies and mosquitoes, respectively. In 2004, the highly pathogenic avian influenza occurred in Kyoto. The H5N1 influenza A virus was isolated from the blow fly, Calliphora nigribarbis, collected around a poultry farm. Exposure experiments showed that the H5N1 virus survived in C. nigribarbis for at least 24 h. C. nigribarbis was suggested to possibly transport the H5N1 virus over a distance of 2 km, which they can access within 24 h. While in 2014, 162 autochthonous dengue cases were reported. Dengue virus was isolated from Aedes albopictus collected in the suspected locations of dengue virus infection in Tokyo. Phylogenetic analysis and virus infection experiments revealed that Ae. albopictus was a major dengue vector in Tokyo in 2014. In both cases, we first collected vector arthropods at each outbreak location to understand their biological characteristics and ecological dynamics. We then detected pathogens from the collected arthropods and conducted infection experiments in the laboratory. We can understand that obtaining data from both the field and the laboratory is necessary to confront arthropod-borne infectious diseases.

Prevalence and burden of dengue infection in Europe: A systematic review and meta-analysis.

Imported dengue cases are thought to be important source for transmission of autochthonous dengue in Europe. We aimed to investigate the prevalence of dengue in Europe, its severity, and factors associated with it. Out of 5287 reports resulting from the search of nine electronic search engines, we included 174 reports. Meta-analysis was performed by pooling the event rate and 95% confidence interval (CI). Subgroup meta-analyses were performed to test the effect of the covariates. Among 20 284 reported cases, 130 autochthonous dengue cases were reported in eight countries with the highest number of cases reported in Israel (n = 41). The highest number of imported dengue cases was in Germany (n = 6638) then France (n = 6610). Most cases were imported from Southeast Asia (n = 2533) especially Thailand. Dengue infection cases increased with time, with 4157 cases reported in 2010. Second dengue infection and dengue serotype 2 were positively associated with dengue severity. The proportion of autochthonous dengue infection increased with time to reach 14.8% (95% CI, 7.6-26.9) in 2015. The pooled proportion of severe dengue was 6.18% (95% CI, 2.7-13.3). The United Kingdom and France had the highest rate of severe dengue (25%; 95% CI, 6.3-62.3, and 21.4%; 95% CI, 24.5-18.7, respectively). This change may be due to the surveillance efforts instead of true biological phenomenon; thus, the lack of surveillance is an obvious limitation. In conclusion, imported and autochthonous dengue has been increasing in Europe. Severe dengue began to increase recently in Europe. European health authorities should pay more attention for the diagnosis and control of dengue infection among returning travelers, especially the travelers with fever of unknown origin.

Environmental factors associated to dengue fever occurrence in the Chapecó municipality, Santa Catarina State

This study aimed to evaluate the influence of environmental factors on the occurrence of dengue and the spatial distribution of the cases in the municipality of Chapecó, Santa Catarina State. Dengue cases were obtained from the Epidemiological Surveillance Department of Santa Catarina and Epidemiological Surveillance of Chapecó. The data of positive containers for Aedes aegypti were obtained from the Environmental Health Surveillance of the municipality. In 2015 and 2016, Chapecó registered 819 autochthonous cases of dengue. It showed a significant relationship between the number of foci of the vector and the minimum and maximum temperatures, as well as the cases of dengue and the population size of the neighborhoods evaluated. This study indicated a multifactorial influence on mosquito proliferation and the occurrence of viral transmission of dengue in the municipality of Chapecó. It reinforces the need of an interdisciplinary approach to prevent and control this endemic disease

The threat of climate change to non-dengue-endemic countries: increasing risk of dengue transmission potential using climate and non-climate datasets

BackgroundDengue is a major public health problem in the tropics and sub-tropics, but the disease is less known to non-dengue-endemic countries including in Northeast Asia. However, an unexpected dengue outbreak occurred in 2014 in Japan. Given that autochthonous (domestic) dengue cases had not been reported for the past 70 years in Japan, this outbreak was highly unusual and suggests that several environmental factors might have changed in a way that favors vector mosquitoes in the Northeast Asian region.MethodsA Climate Risk Factor (CRF) index, as validated in previous work, was constructed using climate and non-climate factors. This CRF index was compared to the number of reported dengue cases in Tokyo, Japan where the outbreak was observed in 2014. In order to identify high-risk areas, the CRF index was further estimated at the 5 km by 5 km resolution and mapped for Japan and South Korea.ResultsThe high-risk areas determined by the CRF index corresponded well to the provinces where a high number of autochthonous cases were reported during the outbreak in Japan. At the provincial-level, high-risk areas for dengue fever were the Eastern part of Tokyo and Kanakawa, the South-Eastern part of Saitama, and the North-Western part of Chiba. While a relatively small number of high-risk areas were identified in South Korea compared with Japan, the high-risk areas in South Korea include popular tourist destinations where international visitors have been increasing.ConclusionThe recent dengue outbreak in Japan may signal that the two adjacent non-dengue-endemic countries are also exposed to the risk of temporal and sporadic behavior of dengue fever. It is critical to understand potential high-risk areas for future outbreaks and to set up appropriate prevention activities at the governmental-level.

Environmental and demographic determinants of dengue incidence in Brazil.

To analyze the spatial distribution of dengue fever cases within an urban area of the São Paulo State, southeast Brazil. Based on a methodology created by the authors, it was possible to organize the Brazilian Census data of 2010 into a regular grid of 250x250 meters each cell. This cell was the unit of analysis. Then, the 1 688 residential addresses of autochthonous dengue cases reported in 2013 in Caraguatatuba city were geocoded to calculate the incidence rate by cell. The dependent variable was the dengue incidence rate and the independent variables were classified into two types: environmental and sociodemographic. Finally, a Zero-Inflated Negative Binomial Regression was performed using the software R. The statistical analysis showed an association between dengue incidence rate and the environmental variable "proximity to strategic points (junk yards, tire repair shops and deposits of recyclable materials)." Dengue was also associated to the sociodemographic variables "proportion of households with per capita income up to 3 minimum wages", "proportion of nonwhite people" and "proportion of not owned households". Dengue is associated to several factors related to its epidemic outbreak. In this complex context, results suggest that this infectious disease is socially conditioned, since it is more likely to reach population groups with specific characteristics, notably those with low socioeconomic status.

Dengue Virus Infection in Aedes albopictus during the 2014 Autochthonous Dengue Outbreak in Tokyo Metropolis, Japan.

In 2014 in Japan, 162 autochthonous dengue cases were reported for the first time in nearly 70 years. Here, we report the results of the detection and isolation of dengue virus (DENV) from mosquitoes collected in Tokyo Metropolis in 2014 and 2015. The phylogenetic relationship among DENV isolates from mosquitoes and from patients based on both the entire envelope gene and whole coding sequences was evaluated. Herein, 2,298 female and 956 male Aedes albopictus mosquitoes were collected at six suspected locations of DENV infection in Tokyo Metropolis from August to October in 2014 and grouped into 124 and 35 pools, respectively, for viral genome detection and DENV isolation. Dengue virus RNA was detected using reverse transcription polymerase chain reaction and TaqMan assays from 49 female pools; 16 isolates were obtained using C6/36 and Vero cells. High minimum infection rates (11.2-66.7) persisted until mid-September. All DENV isolates belonged to the genotype I in serotype 1 (DENV-1), and its sequences demonstrated > 99% homology to the sequence of the DENV isolated from a patient in the vicinity of Tokyo Metropolis in 2014. Therefore, Ae. albopictus was a major DENV vector, and a single DENV-1 strain circulated in Tokyo Metropolis in 2014. Dengue virus was not detected from male mosquitoes in 2014 and wild larvae in April 2015. Thus, the possibility of both vertical transmission and overwintering of DENV was extremely low, even in dengue-epidemic areas. This study reports the first entomological information on a dengue outbreak in a temperate region, where no Aedes aegypti mosquitoes are distributed.

Low socioeconomic condition and the risk of dengue fever: A direct relationship

This study aimed to characterize the first dengue fever epidemic in Várzea Paulista, São Paulo, Brazil, and its spatial and spatio-temporal distribution in order to assess the association of socioeconomic factors with dengue occurrence. We used autochthonous dengue cases confirmed in a 2007 epidemic, the first reported in the city, available in the Information System on Diseases of Compulsory Declaration database. These cases where geocoded by address. We identified spatial and spatio-temporal clusters of high- and low-risk dengue areas using scan statistics. To access the risk of dengue occurrence and to evaluate its relationship with socioeconomic level we used a population-based case-control design. Firstly, we fitted a generalized additive model (GAM) to dengue cases and controls without considering the non-spatial covariates to estimate the odds ratios of the occurrence of the disease. The controls were drawn considering the spatial distribution of the household of the study area and represented the source population of the dengue cases. After that, we assessed the relationship between socioeconomic variables and dengue using the GAM and obtained the effect of these covariates in the occurrence of dengue adjusted by the spatial localization of the cases and controls. Cluster analysis and GAM indicated that northeastern area of Várzea Paulista was the most affected area during the epidemic. The study showed a positive relationship between low socioeconomic condition and increased risk of dengue. We studied the first dengue epidemic in a highly susceptible population at the beginning of the outbreak and therefore it may have allowed to identify an association between low socioeconomic conditions and increased risk of dengue. These results may be useful to predict the occurrence and to identify priority areas to develop control measures for dengue, and also for Zika and Chikungunya; diseases that recently reached Latin America, especially Brazil.