A literature survey and analysis was conducted to describe the epidemiology of dengue disease in Brazil reported between 2000 and 2010. The protocol was registered on PROSPERO (CRD42011001826: http://www.crd.york.ac.uk/prospero/display_record.asp?ID=CRD42011001826). Between 31 July and 4 August 2011, the published literature was searched for epidemiological studies of dengue disease, using specific search strategies for each electronic database. A total of 714 relevant citations were identified, 51 of which fulfilled the inclusion criteria. The epidemiology of dengue disease in Brazil, in this period, was characterized by increases in the geographical spread and incidence of reported cases. The overall increase in dengue disease was accompanied by a rise in the proportion of severe cases. The epidemiological pattern of dengue disease in Brazil is complex and the changes observed during this review period are likely to have been influenced by multiple factors. Several gaps in epidemiological knowledge regarding dengue disease in Brazil were identified that provide avenues for future research, in particular, studies of regional differences, genotype evolution, and age-stratified seroprevalence.
Dengue disease is the most prevalent arthropod-borne viral disease in humans and is a global and national public health concern in Brazil. We conducted this review to consolidate and describe the existing evidence on the epidemiology of dengue disease in Brazil, between 2000 and 2011, to gauge the recent national and regional impact of dengue disease and provide a basis for setting research priorities and prevention efforts. We used well-defined methods to search and identify relevant research, according to predetermined inclusion criteria. Despite control measures, the increased territorial distribution of the mosquito vector and the co-circulation of multiple dengue virus serotypes have resulted in increases in the incidence and distribution of dengue disease. The number of disease-related hospitalizations and deaths has also increased. Efforts to control the increasing disease incidence have been unsuccessful. This review of dengue disease epidemiology will help enhance knowledge and future disease management. Despite the high volume of research retrieved, we have identified several avenues for future research, in particular studies of regional differences, genotype evolution and age-stratified seroprevalence that will improve our knowledge of dengue disease, contribute to a more accurate estimate of global disease incidence, and also inform evidence-based policies for dengue disease prevention.
Citation: Teixeira MG, Siqueira, JB Jr, Ferreira GLC, Bricks L, Joint G (2013) Epidemiological Trends of Dengue Disease in Brazil (2000–2010): A Systematic Literature Search and Analysis. PLoS Negl Trop Dis 7(12): e2520. doi:10.1371/journal.pntd.0002520
Editor: Thomas R. Unnasch, University of South Florida, United States of America
Received: April 24, 2013; Accepted: September 18, 2013; Published: December 19, 2013
Copyright: © 2013 Teixeira et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: Sanofi Pasteur sponsored this survey and analysis. The literature review group (including members of Sanofi Pasteur) was responsible for the conception of the literature analysis, development of the protocol, data collection, analysis and interpretation of data, provision of critical comments, writing the paper and approving the final version to be published. All authors were involved in the decision to submit this paper for publication in PLoS NTD.
Competing interests: The authors have declared the following competing interests: MGT and JBS declare that they have no conflicts of interest. MGT is sponsored by CNPQ/Brazil. JBS is a consultant to the Ministry of Health, Brasília, Brazil. MGT and JBS received no payments in respect of their work on this review. LB is employed by Sanofi Pasteur and GLCF was employed by Sanofi Pasteur at the time of writing. GJ is employed as a medical writer by Communigen Ltd. All authors confirm that they had full access to all data and had final responsibility for the decision to submit for publication. This does not alter our adherence to all PLOS policies on sharing data and materials.
Dengue disease is an escalating public health problem . Approximately 2·5 billion people live in over 100 endemic countries, predominantly in tropical areas where dengue viruses (DENV) can be transmitted . DENV are arboviruses that are transmitted to humans by infected Aedes aegypti (Linnaeus) mosquitoes – the primary vector. Infection with any one of four DENV serotypes (DENV-1, -2, -3, or -4) can produce a spectrum of illness ranging from a mild, non-specific febrile syndrome, to classic dengue fever (DF), or severe disease forms, such as dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS), that can be fatal. The World Health Organization (WHO) estimates that >50 million dengue infections and >20,000 dengue-related deaths occur annually , , . A recent disease distribution model has estimated there to be 390 (95% credible interval 284–528) million dengue infections per year, of which 96 million are apparent (i.e., cases manifest any level of clinical or sub-clinical severity) . During 2001–2007, >4 million cases were notified in the Americas, and during 1995–2002, >75% of these cases were reported from Brazil , .
Ae. aegypti was eradicated from Brazil as a result of a Pan American Health Organization (PAHO) programme to control the spread of yellow fever. Additionally, DENV transmission was also suppressed in the Americas during the eradication programme. South American countries became re-infested with Ae. aegypti after the programme was discontinued and this, combined with the co-circulation of multiple DENV serotypes, led to the spread of dengue disease across the continent , –.
In 1982, there was a dengue outbreak in a small city in the northern region of Brazil (Boa Vista/Roraima), which was quickly brought under control and the virus did not spread . In 1986, the re-emergence of DENV-1 in Rio de Janeiro state  resulted in over 60,000 reported cases in 1987 and the subsequent spread of DENV increased national public health concerns –. Since the late 1980's the incidence of dengue disease continued to increase; 204,000 cases were reported nationally in 1999 , . By 2000, DENV transmission was reported in 22/27 Brazilian states, and the mosquito vector was present in all states .
Much of Brazil is affected by a tropical wet and dry climate with high temperatures, high humidity and seasonal variations in rainfall; climate patterns that can provide appropriate conditions for breeding and survival of the Ae. aegypti mosquito. The country is divided into five regions (North, Northeast, Central-West, Southeast, and South) comprising 26 states and the federal district containing the capital city, Brasília. In 2000 there were nearly 170 million inhabitants of Brazil, increasing to more than 190 million in 2010 , the majority of whom live in the large cities of the Southeast and Northeast regions .
The National System for Surveillance and Control of Diseases (SNVS) of Brazil, operates as part of the national health system (Sistema Único de Saúde, or SUS). All reported cases from public health services or private health providers are included in the notification database (Sistema de Informacoes de Agravos de Notificacao [SINAN]), which is openly accessible via the internet . Until 2011, the SNVS adopted the case definitions outlined in WHO guidelines , . In 1997, the WHO categorized symptomatic dengue disease as: undifferentiated fever, DF and, DHF . DHF was further classified into four severity grades, with grades III and IV being defined as DSS. However, difficulties in applying the criteria for DHF , led the WHO to suggest a new classification based on levels of severity: non-severe dengue disease with or without warning signs, and severe dengue disease . During 2000–2011, both surveillance and hospitalization reporting systems in Brazil used DF and DHF; the surveillance system used an additional classification designated ‘DF with complications’ (DFC) . Importantly, the articles included in this literature analysis that were based on secondary data used these surveillance sources.
Our objectives of this literature search and analysis were to describe the epidemiology of dengue disease (national and regional incidence [by age and sex], seroprevalence and serotype distribution and other relevant epidemiological data) in Brazil during 2000–2011, and to identify gaps in epidemiological knowledge requiring further research.
A literature review group, including authors of this contribution, developed a literature survey and analysis protocol based on the preferred reporting items of systematic reviews and meta-analyses (PRISMA) guidelines . Our protocol prescribed well-defined methods to search, identify, and select relevant research, and set predetermined inclusion criteria. The protocol was registered on PROSPERO, an international database of prospectively registered systematic reviews in health and social care managed by the Centre for Reviews and Dissemination, University of York (CRD42011001826: http://www.crd.york.ac.uk/prospero/display_record.asp?ID=CRD42011001826; protocol: http://www.crd.york.ac.uk/PROSPEROFILES/1826_PROTOCOL_20130401.pdf) on 9 December 2011.
Search strategy and selection criteria
Between 31 July 2011 and 4 August 2011, we searched databases of published literature (Table 1) for epidemiological studies of dengue disease in Brazil. Search strategies for each database were described with reference to the expanded Medical Subject Headings (MeSH) thesaurus, encompassing the terms ‘dengue’, ‘epidemiology’, and ‘Brazil’. Google and Yahoo searches (limited to the first 50 results) were used to identify national and international reports and guidelines, congress abstracts, and grey literature (e.g., Ministry of Health data, lay publications).
To reduce selection bias, peer-reviewed contributions in English, Portuguese, or Spanish published between 1 January 2000 and 4 August 2011 were included; no limits by sex, age, ethnicity of study participants, or by study type were imposed. Single-case reports and articles only reporting data prior to 1 January 2000 were excluded. Unpublished reports were included if they were identified in one of the sources listed above. Data from grey materials supplemented that from peer-reviewed literature. Publications not identified in the target databases by the search strategy (e.g., locally published papers) and unpublished data sources meeting the inclusion criteria (e.g., theses, Ministry of Health data) were included if recommended by members of the literature review group. Editorials and data from literature reviews of previously published peer-reviewed studies were excluded.
Duplicates and articles not satisfying the inclusion criteria were removed following review of the titles and abstracts. A further selection was made based on review of the full text from the first selection of references. Included publications were summarised using a data extraction instrument developed as a series of spreadsheets. Due to the expected heterogeneity of eligible studies in terms of selection, and number and classification of cases, a meta-analysis was not conducted. For the purposes of the analysis we defined national epidemics as those years with an incidence/100,000 above the 75th percentile for the period. A trend analysis was conducted on the national incidence and case number data.
Results and Discussion
All references identified in the on-line database searches were assigned a unique identification number. Following the removal of duplicates and articles that did not satisfy the inclusion criteria from review of the titles and abstracts, the full papers of the first selection of references were retrieved either electronically or in paper form. A further selection was made based on review of the full text of the articles.
During the period 2000–2010, the incidence of dengue disease in Brazil varied substantially, reaching a peak in 2010 of >1 million cases (538/100,000 inhabitants) and the lowest value was approximately 72,000 cases in 2004 (63.2/100,000 inhabitants) (Table 2, Figure 2A–C, Table S2) , , , –. Despite the yearly variations and cyclical epidemics, trend analysis of the incidence of dengue in Brazil in the period 2000–2010 showed an overall increase in incidence over time that was not statistically significant (β = 12·9/cases per 100,000, p = 0·49). Analysis of the number of cases of dengue disease over the review period shows a growth trend that was not statistically significant (β = 47·984 cases/year, p = 0·25). Nevertheless, the trend analysis suggests a worsening of the problem over time.
(A) Reported number and average incidence per 100,000 population of probable* cases of dengue disease. (B) Reported number of cases of dengue fever with complications (DFC) and dengue haemorrhagic fever (DHF). (C) Reported number of dengue disease related hospitalizations (DFC+DHF) and deaths due to DFC and DHF. (D) Number of Ae. aegypti-infested municipalities. (E). Average incidence of dengue disease per 100,000 population, by region. The epidemiology of dengue disease in Brazil during the review period suggests that incidence and disease severity increased over the decade, although the situation is complicated by national epidemics in 2002, 2008 and 2010. The incidence of dengue disease over the review period reflects the wide distribution of Ae. aegypti nationally. In most regions the dengue disease incidence followed national trends. (Adapted from Teixeira 2009  and Siqueira 2010 ; additional data supplied by Teixeira MG and Siqueira JB, 2012).
There were three national epidemics (years with incidence above the 75th percentile for the period [279.95]) in 2002, 2008 and 2010. In 2002 there were 684,527 to 794,219 probable cases of DF, in 2008, 637,663 to 806,036 cases , , , and in 2010 there were over 1 million reported cases (Table 2; Figure 2A) . A trough occurred in 2004 (71,847 to 113,000 cases) , , , , representing <10 times the number reported in the peak year, 2010 (Table 2; Figure 2A).
The number of reported severe cases also varied by year and the annual proportion of DF manifest as DHF was 0.1–0.5% over the review period. In 2000, the annual number of DHF cases was between 40 and 4502 , , , , . The number of DHF cases during 2000–2010 (>18,000) is striking when compared with data from the previous decade: during the 1990s <1000 cases of DHF were reported . The years in which numbers of DHF cases peaked reflected the national epidemic years for dengue disease described above, with high numbers of DHF cases in 2002 and 2008 (Figure 2B). The 2008 national epidemic of DF/DHF continued with elevated incidence into 2009/2010, with nearly 4000 cases of DHF reported in 2010 .
The proportion of severe cases reported is typical of countries in the Americas, but is low compared with Asia where the reported incidence of DHF is much greater . In similar-sized populations, attack rates for severe dengue disease are 18 times greater in Southeast Asia than in the Americas . However, differences in health surveillance system reporting guidelines and variations in case management practices may contribute to the differences in the number of cases reported, and limit the ability to make valid comparisons . In Brazil, DHF cases are defined by strict application of all four criteria from the 1997 WHO guidelines, which is not the case elsewhere .
Similarly, hospitalizations related to dengue disease increased over the survey period to >94,000 hospitalizations in 2010 (Figure 2C) . The incidence of dengue-related hospitalization was 31·6/100,000 population during the 2002 national epidemic, approximately 40·8/100,000 during the 2008 national epidemic, and 49·7/100,000 during the 2010 national epidemic . These increases in hospitalization rates during epidemic years might suggest an increase in the severity of dengue disease in Brazil, although an increased awareness during epidemics and a lower threshold for hospitalization might also account for these increases.
The number of dengue-related deaths followed the same patterns as the other epidemiological indices of dengue disease. In 2010, of 13,909 cases classified as DFC and 3807 classified as DHF, there were 370 and 308 fatal cases, respectively. The overall number of DHF- or DFC-related deaths was 678 compared with only 19 in 2004 (Figure 2C) .
A seasonal pattern of dengue disease was observed in those studies with available seasonal case distribution data. The highest incidences occurred during January–June –, corresponding to the period of highest rainfall and humidity, providing suitable conditions for Ae. aegypti breeding and survival. The study by Goncalves Neto et al.  showed that 83·3% of dengue disease cases occurred during the rainy season and demonstrated a positive Pearson correlation with the amount of rainfall (r = 0·84) and relative humidity (r = 0·76) and a negative correlation with temperature (r = −0·78).
We found published regional data for part of the study period from four of the five Brazilian regions , , , , –. No published data were recovered for the North region. The available data show that incidence rates varied greatly throughout the country (data not shown; Table S3). In a study of 146 Brazilian cities in October 2006, incidence rates (per 100,000 population) in the 61 cities that reported >500 dengue disease cases ranged between 24·70 (Sao Paulo) and 6222·71 (Campo Grande) . By the end of 2006, 25 of the 27 states had reported local dengue epidemics .
The geographic distribution of the Ae. aegypti vector has widened over the 11-year review period, involving an increasing number of municipalities (Figure 2D) and this has resulted in a broader regional distribution of dengue disease. In most regions the dengue disease incidence followed national trends (Figure 2E). In the early years of the survey, the Southeast and Northeast regions were most affected by DENV infections, whereas from 2009 more cases were reported from studies within the Central-West region. Incidence rates reported in the South region were consistently lower than in other regions. The distribution of reported cases of dengue disease during the 2010 national epidemic was different from that in the 2002 and 2008 national epidemics with high attack rates observed over larger areas of Brazil . These regional variations in dengue disease incidence are unsurprising given the geographically diverse nature of Brazil with its large variations in climate and population density.
Demographic patterns of dengue disease in Brazil
A change in the age distribution of dengue disease over the survey period was evident from the available data. Young adults were most affected by DF and DHF during 2000–2007 and 2000–2005, respectively (i.e., DHF was coincident with the highest incidence of DF). However, in 2006 the incidence of DHF among children aged <5 years increased (0·47/100,000) and was higher than among those aged 10–19 years and 20–39 years (0·36/100,000 and 0·46/100,000, respectively) . During 1998–2006, most DHF cases were in the 20- to 40-year age group, whereas in 2007 >53% of DHF cases occurred in children <15 years of age . In 2007, a large proportion of cases of dengue-related hospitalizations (40.8%) occurred among those aged <10 years. Furthermore, children aged 5–9 years and 10–14 years showed marked increases in hospitalization rates (68·2 and 60·6/100,000 population, respectively) during the 2008 national epidemic, compared with during the 2002 national epidemic (15·9 and 23·1/100,000 population, respectively) . These hospitalization data are in agreement with the distribution of hospitalizations for dengue disease according to age for 2002–2011 (Figure 3) , which suggests a change in age pattern in 2007–2008 (a reduction in the first quartile age) although data from 2009 suggest this change may have been transient. The median age of death from DF was approximately 38 years in 2002 and fell to 30 years between 2007 and 2009 .
A reduction in the first quartile of dengue disease hospitalizations is evident in 2007–2008, although data from 2009 suggest this change may have been transient. Data are median, first and third quartiles, and minimum and maximum ages; the dashed line indicates age 15 years. (Siqueira 2010 . Figure updated and reproduced with kind permission from the Secretariat of Health Surveillance (SVS) of the Ministry of Health of Brazil; additional data supplied by Siqueira JB, 2012).
Regional age-related data from eligible studies are sparse and inter-regional comparisons are difficult (Table 3) , –, , . The most comprehensive data are for 2001–2008 from Ceará state, Northeast region . In 2001, the highest incidence of cases occurred in those aged 20–59 years, whereas in the 2008 national epidemic, those mostly affected were aged <10 years. These data reflect the national changes in age distribution of dengue disease.
Slightly more women than men are affected by dengue disease throughout Brazil , which is similar to the sex distribution of reported cases in other Latin American countries . During 2001–2010 the male∶female ratio of reported cases ranged from 0·75–0·82 , . Regional data were more variable. In 2000 the ratio was 1·09 in the city of São Luís , and 0·5 in the City of Santos in 2010 . Women with dengue disease were slightly older than men (mean age 33·7 years versus 30·2 years, respectively; p = 0.019) .
Seroprevalence data provide further information to illustrate epidemiological trends (see Socio-demographic factors below). Population seroprevalence estimates varied throughout Brazil during the decade analysed. In individuals aged 18–65 years, the highest seroprevalence rates were reported in the cities of Mossoró and Caruaru (97·8% and 94·5%, respectively) with lower seroprevalence reported in Rio Branco (69·2%) and Macapá (48·4%) . In serological surveys of volunteers without DF symptoms in Goiânia, seroprevalence was 29·5% in 2001 and 37·3% in 2002 . In Recife, a large urban centre, during 2004–2006, 354 (53·8%) of 658 patients with suspected DENV infections had antibodies to DENV, of which 175 (49·4%) were characterized as primary infections and 179 (50·6%) as secondary infections . In 2002, the seroprevalence in Recife was 76·3% (45 cases) . Few age-specific seroprevalence data were reported in studies included in our analysis.
Seroprevalence data also reveal that dengue disease is under-reported. Current passive surveillance systems do not report on mildly symptomatic and non-specific febrile cases and do not represent the true rate of infection and transmission. Based on the findings of a seroepidemiological study in Recife conducted between August and September 2006, Rodriguez-Barraquer et al. calculated that <10% of infections may be reported . Comparing the estimated number of individuals with DENV antibodies in three districts of Belo Horizonte in 1996–2006 (79,000) with the number of reported cases (32,330), Pessanha et al. suggested that the number of seropositive cases is 2·5 times higher than the number of reported cases .
National serotype incidence data were not reported in publications identified by the review protocol. Until 2008, most dengue disease diagnoses in Brazil were made using clinical and epidemiological criteria, as isolation and identification of DENV by polymerase chain reaction was scarce. The Brazilian Ministry of Health compiled a series of DENV isolations from 2000–2008, indicating a high proportion of DENV-1 incidence at the beginning of the decade; DENV-3 became predominant from 2003 and DENV-2 was important from 2007 (Figure 4A). The studies we reviewed also indicate a shift to DENV-3 predominance towards the middle of the decade across Brazil, with DENV-2 becoming more important in later outbreaks.
The Brazilian Ministry of Health data from 2000–2008, indicated co-circulation of multiple DENV serotypes with a high proportion of DENV-1 incidence at the beginning of the decade; DENV-3 became predominant from 2003 and DENV-2 was important from 2007. DENV-4 was not present in Brazil until 2011. A similar pattern was observed in the Northeast region state of Ceará. (A: data supplied by Teixeira MG, 2012; B: Cavalcanti 2011 ).
Serotype distribution data reveal trends similar to the national trends, with some local differences (Table 4) , , , , , , , –. The most comprehensive regional data are available for the Northeast region states of Ceará  and Pernambuco , and the Central-West region city of Goiânia . In Ceará a similar pattern of serotype change was reported during 2000–2003, with a shift from DENV-1 and -2 to DENV-3 (Figure 4B). By 2003, almost all infections in the Northeast region were caused by DENV-3, as were three-quarters of those in Goiânia. In contrast, in Rio de Janeiro (Southeast region), the serotype shift may have occurred earlier, with DENV-3 accounting for 99% of infections in 2001  and 2002 . However, for the period 2001–2002, Passos et al. reported only 65·7% DENV-3 serotypes for Rio de Janiero . In the North region city of Manaus, Amazonas state, an outbreak in 2006–2007 was attributed to DENV-3, comprising 100% of the serotypes identified in 2006, falling to 78·7% in 2007 . Data from Ceará state are also available for the second half of the survey period (to 2008) . These show a shift from DENV-3 to DENV-2 in 2007 and 2008. Regional data for 2007 onwards, other than those for Ceará state, were not published during the survey period.
A report of the first DENV-4 isolate for 25 years in Amazonas in 2008 , was followed in July 2010 by its re-emergence in Boa Vista, the capital of Roraima State, after an absence of 28 years . DENV-4 infections have since been reported in the Northeast (Piauí, Pernambuco, Bahia, and Ceará) and the Southeast (Rio de Janeiro and São Paulo) . A serotype-specific NS1 enzyme-linked immunosorbent assay test has been introduced in some states by the Brazilian Ministry of Health as a screening tool to aid determination of the circulating serotypes.
An increase in the magnitude of national epidemics and in the severity of dengue disease in Brazil was observed during the review period (Figure 2A–F). It has been suggested that severe forms of dengue disease in children may be linked to an increased prevalence of DENV-2 versus DENV-3 . However, we do not believe that changes in circulating DENV serotypes are solely responsible for the changes in incidence of DHF observed during this review period. The changes observed during this review period are likely to have been influenced by multiple factors, including regional variations in circulating DENV serotypes, virulence of viral strains, serotype-specific herd immunity in different age groups, and the density of the vector population.
Several studies reported clinical differences in patients with dengue disease associated with distinct DENV serotypes. Pereira et al. reported that individuals infected by DENV-3 presented with signs of more severe disease than those associated with DENV-1 or DENV-2 . However, a study by Feres et al. in all age groups (age range, 1–60 years) diagnosed with dengue disease in a region of central Brazil, found that the emergence of DENV-3 in this region was not associated with increased disease severity .
Although an increase in the severity of dengue disease outcomes in patients with a secondary infection due to a different serotype has been proposed , secondary infection was not a predictor of severity in a cohort of adults with confirmed dengue disease (predominantly infected with DENV-3) in central Brazil in 2005 . The relationship between primary and secondary infection, the infecting DENV serotype, and disease severity remains unclear.
Few age-specific serotype data were reported in published studies. In the Greater Metropolitan Region of the State of Rio de Janeiro in 2000–2001, 5324 serum samples were analysed from patients with suspected dengue disease . The mean ages of patients according to infecting serotype were not significantly different (p = 0.108): DENV-1 (30·9±15·9 years), DENV-2 (34·3±15·0 years), and DENV-3 (30·9±14·6 years).
Several studies examined associations between the risk for dengue disease and socio-economic, demographic and infrastructure characteristics. A matched case–control study conducted in Salvador (2002–2003) and Fortaleza (2003–2005) in DENV seropositive individuals demonstrated a significant association between DHF and both high income and increased years of schooling . In another study one-storey homes and a high number of residents per household were identified risk factors for dengue disease . However, Mondini et al. found that DENV transmission was independent of socio-economic strata for the years within the survey period . In a study of DENV-3 emergence and dispersion dynamics in the state of Bahia, viral circulation intensity was strongly dependent on increased population density and availability of susceptible individuals . Teixeira et al. demonstrated a high risk for dengue disease in towns characterized by urbanization, poor sewer networks, and limited piped water supplies .
In Belo Horizonte, 89,607 cases registered in the surveillance system from 1996–2002 were analysed according to defined high- and low-risk areas . Factors significantly associated with high-risk compared with low-risk areas were lower income of the head of the family, higher household density, and larger proportion of children and elderly women . A seroepidemiological study of a random sample of 627 individuals during January 2000 in the same municipality, showed that low income was also associated with high seroprevalence rates. Other variables associated with high seroprevalence rates were residence in horizontal residential buildings with vector infestation and a lack of spatial mobility of residents . During 2005–2006, a household survey was performed in 2833 individuals aged 5–64 years in three diverse socio-economic and environmental areas of Recife. The DENV seroprevalence was 91·1%, 87·4%, and 74·3% in the deprived, intermediate, and high socio-economic areas, respectively, revealing an inverse relationship between high seroprevalence and low socio-economic status . In a similar serological survey in Recife conducted between August and September 2006, three neighbourhoods were selected to represent low (area 1), medium (area 2), and high (area 3) socio-economic areas. Among the 1427 individuals included (aged 5–20 years), seroprevalence was 85%, 70%, and 82% in areas 1, 2, and 3, respectively . In a study in three health districts in the city of Belo Horizonte conducted among 709 individuals between June 2006 and March 2007, seroprevalence was 11·9% (95% confidence interval 9·7–14·6). Seropositivity was associated with construction type (apartment or house/shanty; apartment was a protection factor) and with an elevated health vulnerability index for the location of the dwelling, but was not associated with sex, age, or family income .
Our literature survey and analysis reveals heterogeneity in the incidence of dengue disease over time and space that is indicative of the complexity of risk factors involved in disease transmission. However, it is likely that unplanned urbanization and changes in land use (deforestation) play a significant role in raising the incidence and prevalence of dengue disease .
Only two of the studies selected for analysis examined the relationship between ethnicity and susceptibility to dengue disease. One study found that both self-defined Afro-Brazilian ethnicity and African ancestry were protective for DHF after controlling for income level . A second study showed that the risk of DHF was 4.6 times higher in those of white ethnicity than those of Afro-Brazilian/African ethnicity .
With regard to the risk associated with comorbidities, an association between diabetes, allergy treated with steroids, and hypertension (in those with Afro-Brazilian/African ancestry) and an increased risk for DHF was demonstrated in a matched case–control study conducted in Salvador (2002–2003) and Fortaleza (2003–2005) in individuals with a serologically confirmed history of dengue disease .
Effectiveness of vector-control measures.
After detection of DENV-3, in Rio de Janeiro in 2000, and the co-circulation of three serotypes (DENV-1, DENV-2, and DENV-3), the Ministry of Health established the National Dengue Control Programme (PNCD) in 2002 to implement new strategies and intensify existing plans with greater operational scope . Pessanha et al. found a reduction in the number of municipalities with dengue incidence >100/100,000 inhabitants from 66·10% in 2001–2002 (before PNCD implementation) to 48·97% in 2003–2006 (after implementation) .
Strengths and limitations of this survey and analysis
Despite some gaps, our literature survey and analysis provides a comprehensive overview of the evolving epidemiology of dengue disease in Brazil over the period 2000–2011. This study has several important strengths. Our survey was thorough; we screened >700 articles to identify relevant publications and we developed a comprehensive data extraction instrument to facilitate the capture of all relevant data.
Nevertheless, the lack of comprehensive and continuous data for the survey period limits our ability to make comparisons and draw firm conclusions over the years, across regions, and among different ages. For example, age-stratified data were not reported systematically and age range boundaries differed by study. Therefore, although we can suggest trends in age distribution, it is not possible to directly compare data from the selected publications.
The inclusion of publications in three languages reduced selection bias in our literature review and analysis. However, despite the inclusion of PhD dissertations and theses there is a bias towards published articles. An assessment of quality of evidence was not carried out and potential weaknesses of some studies such as inadequately described case selection, small sample sizes, and unspecified statistical methods were not reasons for exclusion. Consequently, any limitations of the original studies are carried forward into our review.
Many of the studies relied on data reported by passive surveillance systems, which can vary between regions and over time  and may misrepresent the number of cases due to changes in reporting behaviour and misclassifications.
Avenues for future research
Our literature survey and analysis identified several knowledge gaps, which indicate potential avenues for future study. In particular, there are gaps relating to the regional incidence of dengue disease in Brazil, national and regional age-related data, and national and regional serotype information. Further epidemiological studies may help to clarify and define regional differences.
The large increase in the number of DHF cases and the shift in age distribution of DHF towards younger age groups that occurred during the 2007–2008 national epidemic warrant explanation. One possibility is that the change in circulating DENV serotypes over time may have affected the pattern of dengue disease epidemiology in Brazil . Age-stratified seroprevalence studies will improve assessment of the level of transmission and inapparent infection, as well as providing information relating to the age shift.
Further studies into the risk factors for dengue disease and its severity are also important. For example, in Southeast Asia, DENV infection has been more widespread for a longer period of time than in the Americas, creating a large group of individuals likely to experience a second or third infection . These secondary infections carry an increased risk of severe dengue disease. The data in this review do not address the Southeast Asian experience and further examination as to whether this phenomenon is replicated in Brazil is required. In addition, few studies in the review specifically measured the effects of urbanization in Brazil, with effects only inferred from studies of other socio-demographic factors. The diversity of ethnic backgrounds within the population suggests that further genetic studies are warranted to determine whether ethnicity affects the clinical expression of dengue disease and the risk for severe outcomes. Studies are also required to clearly define associations with other diseases if comorbidity screening is to be used to identify patients at a greater risk of developing DHF.
We acknowledge that there are gaps in our epidemiological knowledge of dengue disease in Brazil, due, in part (as in many other countries) to the inherent weaknesses of passive surveillance systems. The majority of infections are clinically non-specific consequently dengue disease is often mis-diagnosed during inter-epidemic periods . The findings presented here are in broad agreement with those of Honório et al. , who found only 23·3% of infections were symptomatic, and with Lima et al. , who showed that the number of cases reported for the Southeast region of Brazil under-represented the number of infected individuals. This was also found in studies conducted in other countries . Only when an epidemic occurs is the full spectrum of the disease recognised. Consequently, the disease is likely to be under-reported during inter-epidemic periods but over-reported during epidemics . Overall, we believe the national surveillance data under-estimate the true incidence of DENV infections. However, extensive representative serological surveys are required to estimate the true rate of infection and transmission and, thus, despite its drawbacks, passive reporting is important for the identification of disease trends over time.
Our review and analysis of the epidemiology of dengue disease in Brazil during the past decade suggests an overall increase in the distribution and severity of dengue disease. During the last decade (2000–2010), a total number of 8,440,253 cases were reported (the highest figure in the history of dengue disease in this region) with the highest number of severe cases (221,043; 2.6%) and fatal cases (3058; 0.036% of the total reported cases and 1.38% of the severe cases) . The 1588 cases of severe dengue disease and 163 deaths reported as of epidemiological week 8 in 2011, represent 67% and 73%, respectively, of the total cases registered in the Americas . The co-circulation of multiple DENV serotypes and high dengue disease endemicity may be responsible for the increased occurrence of severe forms of dengue disease and increases in the numbers of dengue disease-related hospitalizations. In addition, the increase in the number of severe cases of dengue disease and a shift in age group predominance of severe forms observed during 2007/08 confirm that dengue disease must remain a public health priority in Brazil.
Even though the studies included in this literature review have improved our understanding of the epidemiology of dengue disease in Brazil, further studies are required to clarify the epidemiological pattern and to understand regional epidemiological differences, the diversity of genotypes of circulating serotypes and the extent of herd immunity by age group. Our review has highlighted the main epidemiological characteristics of dengue in Brazil in the first decade of this century and revealed that the epidemiological pattern of dengue disease in Brazil is complex. The changes observed are likely to have been the result of multiple factors, which still require elucidation.
PRISMA 2009 checklist.
Citations used in the literature analysis.
Incidence of dengue disease in Brazil: national data.
Incidence of dengue disease in Brazil: regional data.
The authors take full responsibility for the content of this contribution but would like to thank Grenville Marsh (Sanofi Pasteur) and Carlos Espinal (Sanofi Pasteur) for provision of critical comments and suggestions on the drafts and Nikki West (Communigen Ltd) for editorial and administrative assistance.
Conceived and designed the experiments: JBS MGT LB GJ. Performed the experiments: JBS MGT LB GJ. Analyzed the data: JBS MGT LB GJ. Wrote the paper: JBS MGT LB GJ. Contributed to the conceptualization and drafting of the article and participated in the data analysis and interpretation, critical review of the article, and final approval of the version to be submitted for publication: JBS MGT LB GJ. Contributed to the conceptualization and drafting of the article, data analysis and interpretation, and final approval of the version to be submitted for publication: GLCF.
- 1. Scientific Working Group on Dengue. (2007) Report of the Scientific Working Group on Dengue, 1–5 October 2006. Geneva: World Health Organization. Available: http://www.who.int/tdr/publications/documents/swg_dengue_2.pdf. Accessed: 30 September 2013
- 2. World Health Organization. (2013) Impact of Dengue. Available: http://www.who.int/csr/disease/dengue/impact/en/. Accessed: 27 September 2013.
- 3. Bhatt S, Gething PW, Brady OJ, Messina JP, Farlow AW, et al. (2013) The global distribution and burden of dengue. Nature 496: 504–507 doi: http://dx.doi.org/10.1038/nature12060.
- 4. World Health Organization. (2012) Dengue and severe dengue. Fact sheet number 117 (Revised January 2012). Available: http://www.who.int/mediacentre/factsheets/fs117/en/index.html. Accessed: 27 September 2013.
- 5. Pan American Health Organization. (2008) Number of reported cases of dengue and dengue hemorrhagic fever (DHF), Region of the Americas (by country and subregion). Washington, DC: Pan American Health Organization; Available: http://www.paho.org/english/ad/dpc/cd/dengue.htm. Accessed: 27 September 2013.
- 6. Nogueira RMR, Miagostovich MP, Schatzmayr HG (2002) Dengue viruses in Brazil. Dengue Bulletin 26: 77–83 Available: http://repository.searo.who.int/handle/123456789/15884. Accessed 30 September 2013.
- 7. Pinheiro FP (1989) Dengue in the Americas, 1980–1987. Epidemiol Bull 10 (1) 1–8.
- 8. Gubler DJ (1989) Aedes aegypti and Aedes aegypti-borne disease control in the 1990s: top down or bottom up. Am J Trop Med Hyg 40: 571–578.
- 9. San Martín JL, Brathwaite O, Zambrano B, Solórzano JO, Bouckenooghe A, et al. (2010) The epidemiology of dengue in the Americas over the last three decades: a worrisome reality. Am J Trop Med Hyg 82: 128–135 doi: http://dx.doi.org/10.4269/ajtmh.2010.09-0346.
- 10. Osanai CH, Travassos da Rosa AP, Tang AT, do Amaral RS, Passos AD, et al. (1983) Dengue outbreak in Boa Vista, Roraima. Preliminary report. Rev Inst Med Trop Sao Paulo 25: 53–4 [Portuguese].
- 11. Schatzmayr HG, Nogueira RMR, Travassos da Rosa APA (1986) An outbreak of dengue virus at Rio de Janeiro. Mem Inst Oswaldo Cruz 81: 245–246.
- 12. Barreto ML, Teixeira MG (2008) Dengue in Brazil: epidemiological situation and contributions for a research agenda. Estud Av 22: 53–72 doi: http://dx.doi.org/10.1590/S0103-40142008000300005.
- 13. Rodriguez-Barraquer I, Cordeiro MT, Braga C, de Souza WV, Marques ET, et al. (2011) From re-emergence to hyperendemicity: the natural history of the dengue epidemic in Brazil. PLoS Negl Trop Dis 5: e935 doi: http://dx.doi.org/10.1371/journal.pntd.0000935.
- 14. Nogueira RMR, de Araújo JMG, Schatzmayr HG (2007) Dengue viruses in Brazil, 1986–2006. Rev Panam Salud Publica 22 (5) 358–363 doi: http://dx.doi.org/10.1590/S1020-49892007001000009.
- 15. Teixeira MG, Costa Mda C, Barreto F, Barreto ML (2009) Dengue: twenty-five years since reemergence in Brazil. Cad Saude Publica (Suppl 1) S7–S18 doi: http://dx.doi.org/10.1590/S0102-311X2009001300002.
- 16. Figueiredo LTM (2010) Dengue in Brazil during 1999–2009: A review. Dengue Bulletin 34: 6–12 Available: http://repository.searo.who.int/handle/123456789/16161. Accessed: 30 September 2013.
- 17. da Rosa JFS. (2000) Dengue epidemic in Belem, Para, Brazil, 1996–97. The Free Library 01 May 2000. Available: http://www.thefreelibrary.com/DengueEpidemicinBelem%2cPara%2cBrazil%2c1996-97.-a062870291. Accessed: 27 September 2013.
- 18. IBGE Brazil.gov.br. (2011) Brazil population reaches 190.8 million. Brazilian Economic News Update Political & Economic Information (Originally published on 29/04/2011 19:19 - Portal Brasil) Available: http://braz-enu.blogspot.co.uk/2011/05/brazil-population-reaches-1908-million.html#/2011/05/brazil-population-reaches-1908-million.html. Accessed: 27 September 2013.
- 19. Figueiredo LTM (2003) Dengue in Brazil: past, present and future perspective. Dengue Bulletin 27: 25–33 doi: http://repository.searo.who.int/handle/123456789/15928.
- 20. Barreto ML, Teixeira MG, Bastos FI, Ximenes RA, Barata RB, et al. (2011) Successes and failures in the control of infectious diseases in Brazil: social and environmental context, policies, interventions, and research needs. Lancet 377: 1877–1889 doi: http://dx.doi.org/10.1016/S0140-6736(11)60202-X.
- 21. World Health Organization. (1997) Dengue hemorrhagic fever: diagnosis, treatment, prevention and control. 2nd edition. Geneva: World Health Organization. Available: http://www.who.int/csr/resources/publications/dengue/Denguepublication/en. Accessed: 27 September 2013.
- 22. World Health Organization. (2009) Dengue: Guidelines for diagnosis, treatment, prevention and control. New edition. Geneva: World Health Organization. Available: http://whqlibdoc.who.int/publications/2009/9789241547871_eng.pdf. Accessed: 27 September 2013.
- 23. Bandyopadhyay S, Lum LC, Kroeger A (2006) Classifying dengue: a review of the difficulties in using the WHO case classification for dengue haemorrhagic fever. Trop Med Int Health 11: 1238–1255 doi: http://dx.doi.org/10.1111/j.1365-3156.2006.01678.x.
- 24. Brasil. Ministério da Saúde. (2005) Secretaria de Vigilância em Saúde. Guia de Vigilância Epidemiológica/Ministério da Saúde, Secretaria de Vigilância em Saúde.-6 ed.- Brasília: Ministério da Saúde 236–237. Available: http://portal.anvisa.gov.br/wps/wcm/connect/3463ca004745920f9a61de3fbc4c6735/Guia_Vig_Epid_novo2.pdf?MOD=AJPERES. Accessed: 30 September 2013.
- 25. Moher D, Liberati A, Tetzlaff J, Altman DG (2009) The PRISMA Group (2009) Preferred Reporting Items for Systematic Reviews and Meta-Analyses: The PRISMA Statement. J Clin Epidemiol 62: 1006–1012 doi: http://dx.doi.org/doi:10.1016/j.jclinepi.2009.06.005.
- 26. Siqueira JB, Vinhal LC, Said RFC, Hoffmann JL, Martins J, et al.. (2010) Chapter 7. Dengue no Brasil: tendencias e mudancas na epidemiologia, com enfase nas epidemias de 2008 e 2010. In: Saúde Brasil 2010: uma análise da situação de saúde e de evidências selecionadas de impacto de ações de vigilância em saúde. Ministério da Saúde, Secretaria de Vigilância em Saúde, Departamento de Análise de Situação em Saúde. Série G. Estatística e Informação em Saúde. ISBN 978-85-334-1851-6. Brasília: Ministério da Saúde, 372 p. Available: http://portal.saude.gov.br/portal/arquivos/pdf/cap_7_saude_brasil_2010.pdf. Accessed: 27 September 2013.
- 27. Da Fonseca GF. (2009) Dengue fever in Brazil: trends, surveillance and outbreak of 2008 [thesis]. GoiâniaBrazil: Universidade Federal de Goiás 1 v. 61 p.
- 28. dos Santos SL. (2003) Assessment of dengue control actions: critical aspects and perception of population – a case study in a northeastern town [thesis]. FiocruzBrazil: Magellan Aggeu Research Center 1 v. 132 p.
- 29. Teixeira Mda G, Costa Mda C, Barreto ML, Mota E (2005) Dengue and dengue hemorrhagic fever epidemics in Brazil: what research is needed based on trends, surveillance, and control experiences? Cad Saude Publica 21: 1307–15 doi: http://dx.doi.org/10.1590/S0102-311X2005000500002.
- 30. Siqueira Junior JB. (2004) Surveillance of dengue fever in urban area: transmission and spatial analysis [thesis]. GoiâniaBrazil: Universidade Federal de Goiás 1 v. 94 p.
- 31. Moraes GH. (2009) Death by severe dengue in Brazil, 2000 to 2005: Correlation of notification in two information systems and case-control study of factors associated with [thesis]. Seattle, WAUSA: University of Washington 1 v. 129 p.
- 32. Halstead SB (2006) Dengue in the Americas and Southeast Asia: do they differ? Rev Panam Salud Publica 20: 407–15 doi: http://dx.doi.org/10.1590/S1020-49892006001100007.
- 33. Beatty ME, Stone A, Fitzsimons DW, Hanna JN, Lam SK, et al. (2010) Best practices in dengue surveillance: a report from the Asia-Pacific and Americas Dengue Prevention Boards. PLoS Negl Trop Dis 4: e890.
- 34. Cordeiro MT, Schatzmayr HG, Nogueira RM, Oliveira VF, Melo WT, et al. (2007) Dengue and dengue hemorrhagic fever in the State of Pernambuco, 1995–2006. Rev Soc Bras Med Trop 40: 605–611 doi: http://dx.doi.org/10.1371/journal.pntd.0000890.
- 35. Gonçalves Neto VS, Rebêlo JM (2004) [Epidemiological characteristics of dengue in the Municipality of São Luis, Maranhao, Brazil, 1997–2002]. Cad Saude Publica 20: 1424–1431 [Portuguese]. doi:http://dx.doi.org/10.1590/S0102-311X2004000500039.
- 36. Cordeiro MT, Silva AM, Brito CA, Nascimento EJ, Magalhães MC, et al. (2007) Characterization of a dengue patient cohort in Recife, Brazil. Am J Trop Med Hyg 77: 1128–1134 Available: http://www.ajtmh.org/content/77/6/1128.long. Accessed: 30 September 2013.
- 37. De Simone TS, Nogueira RM, Araújo ES, Guimarães FR, Santos FB, et al. (2004) Dengue virus surveillance: the co-circulation of DENV-1, DENV-2 and DENV-3 in the State of Rio de Janeiro, Brazil. Trans R Soc Trop Med Hyg 98: 553–562 doi: http://dx.doi.org/10.1016/j.trstmh.2003.09.003.
- 38. Siqueira JB Jr, Martelli CM, Coelho GE, Simplicio AC, Hatch DL (2005) Dengue and dengue hemorrhagic fever, Brazil, 1981–2002. Emerg Infect Dis 11: 48–53 doi: http://dx.doi.org/10.3201/eid1101.031091.
- 39. Cavalcanti LP, Vilar D, Souza-Santos R, Teixeira MG (2011) Change in age pattern of persons with dengue, northeastern Brazil. Emerg Infect Dis 17: 132–134 doi: http://dx.doi.org/10.3201/eid1701.100321.
- 40. De Souza TsBB, Dias JP (2010) [Epidemic profile of dengue in the municipal district of Itabuna (BA), 2000 Jun. 2009]. Rev Baianade Saude Publica 34: 665–681 [Portuguese].
- 41. Da Silva JB. (2009) Quality of information systems and SINAN-SIH SUS and the proportion of severe cases of dengue in the city of Goiânia-Go, 2005–2008: estimation by the method of capture–recapture [thesis]. GoiâniaBrazil: Universidade Federal de Goiá 1 v. 56 p.
- 42. Cardoso IM, Cabidelle AD, Borges PD, Lang CF, Calenti FG, et al. (2011) Dengue: clinical forms and risk groups in a high incidence city in the southeastern region of Brazil. Rev Soc Bras Med Trop 44: 430–435 doi: http://dx.doi.org/10.1590/S0037-86822011005000044.
- 43. Koyama AM, Baldissera VDA (2009) [Description of the cases of dengue fever in the southern states of Brazil, 2001–2005]. Arquivos de Ciências da Saúde da UNIPAR 13: 125–132 [Portuguese].
- 44. Montenegro D, Lacerda HR, Lira TM, Oliveira DS, Lima AA, et al. (2006) [Clinical and epidemiological aspects of the dengue epidemic in Recife, PE, 2002]. Rev Soc Bras Med Trop 39: 9–13 [Portuguese]. doi:http://dx.doi.org/10.1590/S0037-86822006000100002.
- 45. Feres VC, Martelli CM, Turchi MD, Junior JB, Nogueira RM, et al. (2006) Laboratory surveillance of dengue virus in Central Brazil, 1994–2003. J Clin Virol 37: 179–183 doi: http://dx.doi.org/10.1016/j.jcv.2006.07.004.
- 46. Gasparetti MV, Castro R, Castro SA, Maria GS, Cotait AdAL, et al. (2007) Dengue incidence in ABCD region. Arq Med ABC 32: 70–73.
- 47. Hino P, dos Santos CC, dos Santos MO, da Cunha TN, dos Santos CB (2010) [Temporal evolution of dengue fever in Ribeirao Preto, Sao Paulo State, 1994–2003]. Cien Saude Colet 15: 233–238 [Portuguese]. doi:http://dx.doi.org/10.1590/S1413-81232010000100028.
- 48. Sampaio AS (2008) [The epidemiologic situation of dengue in Salvador (BA), 2000–2005]. Rev Baiana Saude Publica 32: 159–167 [Portuguese].
- 49. de Castro JA, de Andrade HM, do Monte SJ, da Silva AS, Gomes KC, et al. (2003) Dengue viruses activity in Piaui, Brazil. Mem Inst Oswaldo Cruz 98: 1021–1023 doi: http://dx.doi.org/10.1590/S0074-02762003000800007.
- 50. Santos CH, Sousa FYd, Lima LRd, Stival MM (2009) Epidemiological profile of dengue in Anapolis municipality, Brazil 2001–2007. Rev Patol Trop 38: 249–259.
- 51. Monteiro ESC, Coelho MnE, Cunha ISd, Cavalcante MdAS, Carvalho FAcdA (2009) [Epidemiological and vector-related indicators of dengue fever in Teresina city, Piaui State, Brazil, from 2002 to 2006]. Epidemiol Serv Saúde 18: 365–374 [Portuguese].
- 52. Coelho GE, Burattini MN, Teixeira MG, Coutinho FA, Massad E (2008) Dynamics of the 2006/2007 dengue outbreak in Brazil. Mem Inst Oswaldo Cruz 103: 535–539 doi: http://dx.doi.org/10.1590/S0074-02762008000600004.
- 53. Teixeira MG, Costa MC, Coelho G, Barreto ML (2008) Recent shift in age pattern of dengue hemorrhagic fever, Brazil. Emerg Infect Dis 14: 1663 doi: http://dx.doi.org/10.3201/eid1410.071164.
- 54. Romano CM, de Matos AM, Araujo ES, Villas-Boas LS, da Silva WC, et al. (2010) Characterization of Dengue virus type 2: new insights on the 2010 Brazilian epidemic. PLoS One 5: e11811 doi: http://dx.doi.org/10.1371/journal.pone.0011811.
- 55. Dias JP. (2006) Evaluation of the effectiveness of the eradication of Aedes Aegypti, programme Brazil, 1996–2002 [thesis]. Salvador, Brazil: Universidade Federal da Bahia 1 v. 79 p.
- 56. Siqueira-Junior JB, Maciel IJ, Barcellos C, Souza WV, Carvalho MS, et al. (2008) Spatial point analysis based on dengue surveys at household level in central Brazil. BMC Public Health 8: 361 doi: http://dx.doi.org/10.1186/1471-2458-8-361.
- 57. Pessanha JE, Caiaffa WT, Kroon EG, Proietti FA (2010) [Dengue fever in three sanitary districts in the city of Belo Horizonte, Brazil: a population-based seroepidemiological survey, 2006 to 2007]. Rev Panam Salud Publica 27: 252–258 [Portuguese]. doi:http://dx.doi.org/10.1590/S1020-49892010000400003.
- 58. Cunha MdCM, Caiaffa WT, Oliveira CdL, Kroon EG, Pessanha JEM, et al. (2008) [Associated factors to infection by dengue virus in the municipality of Belo Horizonte, State of Minas Gerais, Brazil: individual characteristics and intra-urban differences]. Epidemiol Serv Saúde 17: 217–230 [Portuguese].
- 59. Nogueira RM, Schatzmayr HG, de Filippis AM, Dos Santos FB, da Cunha RV, et al. (2005) Dengue virus type 3, Brazil, 2002. Emerg Infect Dis 11: 1376–1381 doi: http://dx.doi.org/10.3201/eid1109.041043.
- 60. Passos MN, Santos LM, Pereira MR, Casali CG, Fortes BP, Ortiz Valencia LI, et al. (2004) [Clinical differences observed in patients with dengue caused by different serotypes in the epidemic of 2001/2002, occurred in Rio de Janeiro]. Rev Soc Bras Med Trop 37: 293–295 [Portuguese]. doi: http://dx.doi.org/10.1590/S0037-86822004000400001.
- 61. Rocha LA, Tauil PL (2009) [Dengue in children: clinical and epidemiological characteristics, Manaus, State of Amazonas, 2006 and 2007]. Rev Soc Bras Med Trop 42: 18–22 [Portuguese]. doi: http://dx.doi.org/10.1590/S0037-86822004000400001.
- 62. Figueiredo RM, Naveca FG, Bastos MS, Melo MN, Viana SS, et al. (2008) Dengue virus type 4, Manaus, Brazil. Emerg Infect Dis 14: 667–669 doi: http://dx.doi.org/10.3201/eid1404.071185.
- 63. Temporao JG, Penna GO, Carmo EH, Coelho GE, do Socorro Silva Azevedo R, et al. (2011) Dengue vírus serotype 4, Roraima State, Brazil. Emerg Infect Dis 17: 938–940 doi: http://dx.doi.org/10.3201/eid1705.101681.
- 64. Ministério da Saúde/Secretaria de Vigilância em Saude MS/SVS (2011) Balanço Dengue. Informe Técnico 1: 1–12 Available: http://portal.saude.gov.br/portal/saude/profissional/area.cfm?id_area=1525. Accessed: 27 September 2013.
- 65. Pereira MN, Jabor LM, Reis MR, Guimaraes C, Menezes BP, et al. (2004) Diferencas clínicas observadas em pacientes com dengue causadas por diferentes sorotipos na epidemia de 2001/2002, ocorrida no municipio do Rio de Janeiro. Rev Soc Brasil Med Trop 37: 293–295 doi: http://dx.doi.org/10.1590/S0037-86822004000400001.
- 66. Halstead SB (1981) The Alexander D. Langmuir Lecture. The pathogenesis of dengue. Molecular epidemiology in infectious disease. Am J Epidemiol 114 (5) 632–648.
- 67. Guilarde AO, Turchi MD, Siqueira JB Jr, Feres VC, Rocha B, et al. (2008) Dengue and dengue hemorrhagic fever among adults: clinical outcomes related to viremia, serotypes, and antibody response. J Infect Dis 197: 817–824 doi: http://dx.doi.org/10.1086/528805.
- 68. Figueiredo MA, Rodrigues LC, Barreto ML, Lima JW, Costa MC, et al. (2010) Allergies and diabetes as risk factors for dengue hemorrhagic fever: results of a case control study. PLoS Negl Trop Dis 4: e699 doi: http://dx.doi.org/10.1371/journal.pntd.0000699.
- 69. Mondini A, Chiaravalloti-Neto F (2008) Spatial correlation of incidence of dengue with socioeconomic, demographic and environmental variables in a Brazilian city. Sci Total Environ 393 (2–3) 241–248 doi: http://dx.doi.org/10.1016/j.scitotenv.2008.01.010.
- 70. Mondini A, Chiaravalloti NF (2007) [Socioeconomic variables and dengue transmission]. Rev Saude Publica 41: 923–930 [Portuguese]. doi:http://dx.doi.org/10.1590/S0034-89102007000600006.
- 71. de Melo PR, Reis EA, Ciuffo IA, Goes M, Blanton RE, et al. (2007) The dynamics of dengue virus serotype 3 introduction and dispersion in the state of Bahia, Brazil. Mem Inst Oswaldo Cruz 102: 905–912 doi: http://dx.doi.org/10.1590/S0074-02762007000800003.
- 72. Teixeira TR, Medronho RA (2008) [Socio-demographic factors and the dengue fever epidemic in 2002 in the State of Rio de Janeiro, Brazil]. Cad Saude Publica 24: 2160–2170 [Portuguese]. doi: http://dx.doi.org/10.1590/S0102-311X2008000900022.
- 73. de Mattos Almeida MC, Caiaffa WT, Assuncao RM, Proietti FA (2007) Spatial vulnerability to dengue in a Brazilian urban area during a 7-year surveillance. J Urban Health 84: 334–345 doi: http://dx.doi.org/10.1007/s11524-006-9154-2.
- 74. Braga C, Luna CF, Martelli CM, de Souza WV, Cordeiro MT, et al. (2010) Seroprevalence and risk factors for dengue infection in socio-economically distinct areas of Recife, Brazil. Acta Trop 113: 234–240 doi: http://dx.doi.org/10.1016/j.actatropica.2009.10.021.
- 75. Blanton RE, Silva LK, Morato VG, Parrado AR, Dias JP, et al. (2008) Genetic ancestry and income are associated with dengue hemorrhagic fever in a highly admixed population. Eur J Hum Genet 16: 762–765 doi: http://dx.doi.org/10.1038/ejhg.2008.4.
- 76. Ministério da Saúde. (2002) Programa Nacional de Controle da Dengue. Brasília: Ministério da Saúde.
- 77. Pessanha JE, Caiaffa WT, Cesar CC, Proietti FA (2009) [Evaluation of the Brazilian National Dengue Control Plan]. Cad Saude Publica 25: 1637–1641 [Portuguese]. doi:http://dx.doi.org/10.1590/S0102-311X2009000700024.
- 78. Costa MdCN, Barreto FR, Coelho GE, Barreto ML, Teixeira MG. (2011) Change in the epidemiologic pattern of occurrence of dengue and dengue hemorrhagic fever in Brazil [poster P 2-508]. World Congress of Epidemiology. Edinburgh, Scotland. 7–11 August 2011.
- 79. Honório NA, Nogueira RM, Codeço CT, Carvalho MS, Cruz OG, et al. (2009) Spatial evaluation and modeling of Dengue seroprevalence and vector density in Rio de Janeiro, Brazil. PLoS Negl Trop Dis 3 (11) e545 doi: http://dx.doi.org/10.1371/journal.pntd.0000545.
- 80. Lima VL, Rangel O, Andrade VR, Silveira NY, Oliveira SS, et al. (2007) [Dengue: sero-epidemiological survey and virological surveillance in Campinas, Sao Paulo, Brazil]. Cad Saude Publica 23: 669–680 [Portuguese]. doi:http://dx.doi.org/10.1590/S0102-311X2007000300025.
- 81. Gubler DJ (2011) Dengue, urbanization and globalization: the unholy trinity of the 21st century. Trop Med Health 39 (4 Suppl) 3–11 doi: http://dx.doi.org/10.2149/tmh.2011-S05.
- 82. Gubler DG (2002) How effectively is epidemiological surveillance used for dengue programme planning and epidemic response. Dengue Bull 26: 96–106 Available: http://repository.searo.who.int/handle/123456789/15902. Accessed: 01 October 2013.
- 83. Guzman MG, Brathwaite O, Enria D, Hunsperger E, Kouri G, et al.. (2011) Dengue in the American Region. An update. Available: http://blog.tropika.net/tropika/files/2011/07/dengue-by-guzman-et-al-jun2011.pdf. Accessed: 27 September 2013.
- 84. Pan American Health Organization. (2011) Epidemiological alert: Update on dengue in the Americas. 19 August 2011. Available: http://new.paho.org/hq/index.php?option=com_docman&task=doc_view&gid=14579&Itemid=1091. Accessed: 27 September 2013.