A SARIMA forecasting model to predict the number of cases of dengue in Campinas, State of São Paulo, Brazil

INTRODUCTION: Forecasting dengue cases in a population by using time-series models can provide useful information that can be used to facilitate the planning of public health interventions. The objective of this article was to develop a forecasting model for dengue incidence in Campinas, southeast Brazil, considering the Box-Jenkins modeling approach. METHODS: The forecasting model for dengue incidence was performed with R software using the seasonal autoregressive integrated moving average (SARIMA) model. We fitted a model based on the reported monthly incidence of dengue from 1998 to 2008, and we validated the model using the data collected between January and December of 2009. RESULTS: SARIMA (2,1,2) (1,1,1)12 was the model with the best fit for data. This model indicated that the number of dengue cases in a given month can be estimated by the number of dengue cases occurring one, two and twelve months prior. The predicted values for 2009 are relatively close to the observed values. CONCLUSIONS: The results of this article indicate that SARIMA models are useful tools for monitoring dengue incidence. We also observe that the SARIMA model is capable of representing with relative precision the number of cases in a next year.

Dengue: aspectos epidemiológicos e o primeiro surto ocorrido na região do Médio Solimões, Coari, Estado do Amazonas, no período de 2008 a 2009

INTRODUÇÃO: A dengue é uma das doenças infecciosas mais frequentes no Brasil e um dos principais problemas de saúde pública no mundo, principalmente em regiões tropicais e subtropicais, com 2,5 a 3 bilhões de pessoas expostas ao risco de serem infectadas atualmente. Deste modo, o presente estudo teve como objetivo demonstrar as características epidemiológicas dos indivíduos acometidos por dengue, sua prevalência e seu processo epidêmico na região do Médio Solimões, Coari, Amazonas, no período de 2008 e 2009. MÉTODOS: Os dados epidemiológicos foram obtidos na Vigilância Epidemiológica da Secretaria Municipal de Saúde da Cidade de Coari-AM. As variáveis analisadas foram: mês da notificação, casos confirmados, gênero (sexo), faixa etária e bairro de residência. RESULTADOS: No total, foram notificados 1.003 casos (635 em 2008 e 368 em 2009), sendo diagnosticados 639 casos positivos. Destes, ± 54% acometerem indivíduos do sexo feminino e ± 46% do sexo masculino. As faixas etárias mais acometidas foram às observadas entre 10-49 anos; quanto à distribuição espacial, observamos o acometimento de indivíduos de bairros próximos a igarapés, lagos e com processo recente e desordenado de habitação. CONCLUSÕES: Deste modo, conclui-se que, durante o período estudado, houve um surto epidêmico de dengue na Cidade de Coari, AM. Entretanto, deve-se considerar que uma epidemia de dengue anterior pode ter ocorrido em Coari, sem que tenha tido o devido diagnóstico etiológico, ou que houveram pessoas com infecção passada que se deslocaram para a capital do Amazonas (Manaus), onde os vírus circulam desde 1998.

Interpretation of the presence of IgM and IgG antibodies in a rapid test for dengue: analysis of dengue antibody prevalence in Fortaleza City in the 20th year of the epidemic

INTRODUCTION: The diagnosis of dengue and the differentiation between primary and secondary infections are important for monitoring the spread of the epidemic and identifying the risk of severe forms of the disease. The detection of immunoglobulin (Ig)M and IgG antibodies is the main technique for the laboratory diagnosis of dengue. The present study assessed the application of a rapid test for dengue concerning detection of new cases, reinfection recognition, and estimation of the epidemic attack rate. METHODS: This was a retrospective, cross-sectional, descriptive study on dengue using the Fortaleza Health Municipal Department database. The results from 1,530 tested samples, from 2005-2006, were compared with data from epidemiological studies of dengue outbreaks in 1996, 2003, and 2010. RESULTS: The rapid test confirmed 52% recent infections in the tested patients with clinical suspicion of dengue: 40% detected using IgM and 12% of new cases using IgG in the non-reactive IgM results. The positive IgM plus negative IgG (IgM+ plus IgG-) results showed that 38% of those patients had a recent primary dengue infection, while the positive IgG plus either positive or negative IgM (IgG+ plus IgM+/-) results indicated that 62% had dengue for at least a second time (recent secondary infections). This proportion of reinfections permitted us to estimate the attack rate as >62% of the population sample. CONCLUSIONS: The rapid test for dengue has enhanced our ability to detect new infections and to characterize them into primary and secondary infections, permitting the estimation of the minimal attack rate for a population during an outbreak.

Simultaneous circulation of all four dengue serotypes in Manaus, State of Amazonas, Brazil in 2011

INTRODUCTION: Manaus, the capital city of the state of Amazon with nearly 2 million inhabitants, is located in the middle of the Amazon rain forest and has suffered dengue outbreaks since 1998. METHODS: In this study, blood samples were investigated using reverse transcriptase-polymerase chain reaction (RT-PCR), aimed at identifying dengue virus serotypes. RESULTS: Acute phase sera from 432 patients were tested for the presence of dengue virus. Out of the 432 patients, 137 (31.3%) were found to be positive. All the four dengue virus serotypes were observed. CONCLUSIONS: The simultaneous circulation of the four dengue serotypes is described for the first time in Manaus and in Brazil.

Identification of dengue viruses in naturally infected Aedes aegypti females captured with BioGents (BG)-Sentinel traps in Manaus, Amazonas, Brazil

IntroductionIn Manaus, the first autochthonous cases of dengue fever were registered in 1998. Since then, dengue cases were diagnosed by the isolation of viruses 1, 2, 3, and 4.MethodsOne hundred eighty-seven mosquitoes were collected with BioGents (BG)-Sentinel traps in 15 urban residential areas in the Northern Zone of Manaus and processed by molecular tests.ResultsInfections with dengue viruses 1, 2, 3, and 4 and a case of co-infection with dengue viruses 2 and 3 were identified.ConclusionsThese findings corroborate the detection of dengue in clinical samples and reinforce the need for epidemiological surveillance by the Health authorities.

Evaluation of the diagnostic value of the tourniquet test in predicting severe dengue cases in a population from Belo Horizonte, State of Minas Gerais, Brazil

Introduction Dengue is prevalent in many tropical and sub-tropical regions. The clinical diagnosis of dengue is still complex, and not much data are available. This work aimed at assessing the diagnostic accuracy of the tourniquet test in patients with suspected dengue infection and its positivity in different classifications of this disease as reported to the Information System for Notifiable Disease in Belo Horizonte, State of Minas Gerais, Brazil between 2001 and 2006. Methods Cross-section analysis of the diagnostic accuracy of the tourniquet test for dengue, using IgM-anti-DENV ELISA as a gold standard. Results We selected 9,836 suspected cases, of which 41.1% were confirmed to be dengue. Classic dengue was present in 95.8%, dengue with complications in 2.5% and dengue hemorrhagic fever in 1.7%. The tourniquet test was positive in 16.9% of classic dengue cases, 61.7% of dengue cases with complications and 82.9% of cases of dengue hemorrhagic fever. The sensitivity and specificity of the tourniquet test were 19.1% and 86.4%, respectively. Conclusions A positive tourniquet test can be a valuable tool to support diagnosis of dengue where laboratory tests are not available. However, the absence of a positive test should not be read as the absence of infection. In addition, the tourniquet test was demonstrated to be an indicator of dengue severity.

Evaluation of the World Health Organization 2009 classification of dengue severity in autopsied individuals, during the epidemics of 2011 and 2012 in Brazil

Abstract: INTRODUCTION: The dengue classification proposed by the World Health Organization (WHO) in 2009 is considered more sensitive than the classification proposed by the WHO in 1997. However, no study has assessed the ability of the WHO 2009 classification to identify dengue deaths among autopsied individuals suspected of having dengue. In the present study, we evaluated the ability of the WHO 2009 classification to identify dengue deaths among autopsied individuals suspected of having dengue in Northeast Brazil, where the disease is endemic. METHODS: This retrospective study included 121 autopsied individuals suspected of having dengue in Northeast Brazil during the epidemics of 2011 and 2012. All the autopsied individuals included in this study were confirmed to have dengue based on the findings of laboratory examinations. RESULTS: The median age of the autopsied individuals was 34 years (range, 1 month to 93 years), and 54.5% of the individuals were males. According to the WHO 1997 classification, 9.1% (11/121) of the cases were classified as dengue hemorrhagic fever (DHF) and 3.3% (4/121) as dengue shock syndrome. The remaining 87.6% (106/121) of the cases were classified as dengue with complications. According to the 2009 classification, 100% (121/121) of the cases were classified as severe dengue. The absence of plasma leakage (58.5%) and platelet counts <100,000/mm3 (47.2%) were the most frequent reasons for the inability to classify cases as DHF. CONCLUSIONS: The WHO 2009 classification is more sensitive than the WHO 1997 classification for identifying dengue deaths among autopsied individuals suspected of having dengue.

Knowledge and practices related to dengue and its vector: a community-based study from Southeast Brazil

Abstract INTRODUCTION: This study investigated the knowledge of users of primary healthcare services living in Ribeirão Preto, Brazil, about dengue and its vector. METHODS: A cross-sectional survey of 605 people was conducted following a major dengue outbreak in 2013. RESULTS: Participants with higher levels of education were more likely to identify correctly the vector of the disease. CONCLUSIONS: The results emphasize the relevance of health education programs, the continuous promotion of educational campaigns in the media, the role of the television as a source of information, and the importance of motivating the population to control the vector.

An outbreak of dengue virus at Rio de Janeiro - 1986

Dengue virus type 1 has been isolated in Aedes albopictus cell strain, from sera of patients living in the Nova Iguaçu county, by Rio de Janeiro. The clinical picture was characterized by fever, headache, retrobulbar pain, backache, pains in the muscles and the joints and prostration. Studies in paired sera confirmed the presence of recent infection by dengue virus type 1. The outbreak reached adjacent areas, including Rio de Janeiro city (May, 1986).

Virological study of a dengue type 1 epidemic at Rio de Janeiro

A dengue outbreak started in March, 1986 in Rio de Janeiro and spread very rapidly to other parts of the country. The great majority of cases presented classical dengue fever but there was one fatal case, confirmed by virus isolation. Dengue type 1 strains were isolated from patients and vectors (Aedes aegypti) in the area by cultivation in A. albopictus C6/36 cell line. The cytopathic effect (CPE) was studied by electron microscopy. An IgM capture test (MAC-ELISA) was applied with clear and reproducible results for diagnosis and evaluation of virus circulation; IgM antibodies appeared soon after start of clinical disease, and persisted for about 90 days in most patients. The test was type-specific in about 50% of the patients but high levels of heterologous response for type 3 were observed. An overall isolation rate of 46,8% (813 virus strains out of 1734 specimens) was recorded. The IgM test increased the number of confirmed cases to 58,2% (1479 out of 2451 suspected cases). The importance of laboratory diagnosis in all regions where the vectors are present is emphasized.

Cytokine responses to Dengue Infection among Puerto Rican Patients

Recently, a strong correlation between high concentration of tumor necrosis factor (TNFalpha) in blood and severity of dengue hemorrhagic fever/dengue shock syndrome has been reported from Asia and the Pacific. We wished to determine if a similar relationship could be found in dengue patients in the Americas where adult patients with severe syndromes have been observed more frequently than in Asia where severe cases have been observed mostly among children. The concentrations of interleukin-1 (IL-1beta) in hospistalized adult groups were significantly lower than that in outpatient adults. In contrast, the levels of interleukin 6 (IL-6) were significantly higher in hospistalized adults and children than in the corresponding outpatients. Levels of TNFalpha were higher in hospistalized children than in outpatient children or hospistalized adults. There was no significant difference in the levels of these three cytokines among hospitalized patients with or without hemorrhagic manifestations. Thus, an elevated IL-6 level was positively associated with severity of dengue infection in both children and adults, but IL-1beta level was negatively associated with severity in adults.

Dengue in Brazil - situation, transmission and control: a proposal for ecological control

This article discusses dengue in terms of its conceptual and historical aspects, epidemiological and clinical/pathological nature, and evolution up to the present situation in Brazil. The author discusses the ecological relationship in both the production of dengue and its control. Comparison is made between traditional dengue-control programs and a proposed socially-controlled program of an ecological nature without the use of insecticides. Stress is placed on interdisciplinary technical and scientific activity, broadbased participation by communities in discussing methodological aspects involving them, and prospective evaluation comparing the communities selected for intervention and control communities with regard to clinical and subclinical dengue cases and vector infestation rates in relation to climatic, socio-economic, and behavioural factors.

Diagnosis of Dengue by Using Reverse Transcriptase-Polymerase Chain Reaction

A rapid identification of dengue viruses from clinical samples by using a nested reverse transcriptase-polymerase chain reaction (RT-PCR) procedure was carried out for diagnostic and epidemiological purposes. RT-PCR identified DEN-1 and DEN-2 viruses in 41% (41/100) of previously confirmed cases and provided an accurate confirmation of DHF in four fatal cases. RT-PCR was also useful for detecting and typing dengue viruses in suspected cases, allowing a rapid identification of new serotypes in endemic areas

Retrospective Study on Dengue in Fortaleza, State of Ceará, Brazil

A retrospective serologic study was carried out in Fortaleza, State of Ceará, Brazil, in order to detect the dengue virus activity before recognizing the epidemic of 1994. Mac-Elisa was performed by using a mixture of specific DEN-1 and DEN-2 antigens on serum samples from the Emilio Ribas Laboratory collection. Samples were obtained from 1,224 patients with exanthematic febrile disease and negative serological results for rubella. All specimens were taken during November 1993 to May 1994. The results confirmed dengue infections in Fortaleza by November 1993, approximately six months before the beginning of the epidemic, proving how misleading diagnosis of dengue infection are still troublesome, in spite of the strong dengue activity in Ceará. The authors stress the urgent necessity to implement the active surveillance system in order to prevent another extensive dengue fever epidemics in the state. Epidemiological background of the dengue activity in the State of Ceará is also described.