Temporal distribution of dengue virus serotypes in Colombian endemic area and dengue incidence: re-introduction of dengue-3 associated to mild febrile illness and primary infection

We have investigated the temporal distribution of dengue (DEN) virus serotypes in the department (state) of Santander, Colombia, in relation to dengue incidence, infection pattern, and severity of disease. Viral isolation was attended on a total of 1452 acute serum samples collected each week from 1998 to 2004. The infection pattern was evaluated in 596 laboratory-positive dengue cases using an IgG ELISA, and PRNT test. The dengue incidence was documented by the local health authority. Predominance of DEN-1 in 1998 and DEN-3 re-introduction and predominance in 2001-2003 coincided with outbreaks. Predominance of DEN-2 in 2000-2001 coincided with more dengue hemorrhagic fever (DHF). DEN-4 was isolated in 2000-2001 and 2004 but was not predominant. There was an annual increase of primary dengue infections (from 13.7 to 81.4%) that correlated with frequency of DEN-3 (r = 0.83; P = 0.038). From the total number of primary dengue infections DEN-3 (81.3%) was the most frequent serotype. DHF was more frequent in DEN-2 infected patients than in DEN-3 infected patients: 27.5 vs 10.9% (P < 0.05). DEN-3 viruses belonged to subtype C (restriction site-specific-polymerase chain reaction) like viruses isolated in Sri-Lanka and other countries in the Americas. Our findings show the importance of continuous virological surveillance to identify the risk factors of dengue epidemics and severity.

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.

Dynamics of the 2006/2007 dengue outbreak in Brazil

We analyzed dengue incidence in the period between October 2006-July 2007 of 146 cities around the country were Larval Index Rapid Assay (LIRA) surveillance was carried out in October 2006. Of these, we chosen 61 cities that had 500 or more cases reported during this period. We calculated the incidence coefficient, the force of infection (») and the basic reproduction number (R0) of dengue in those 61 cities and correlated those variables with the LIRA. We concluded that » and R0 are more associated with the number of cases than LIRA. In addition, the average R0 for the 2006/2007 dengue season was almost as high as that calculated for the 2001/2002 season, the worst in Brazilian history.

The spatiotemporal trajectory of a dengue epidemic in a medium-sized city

Understanding the transmission dynamics of infectious diseases is important to allow for improvements of control measures. To investigate the spatiotemporal pattern of an epidemic dengue occurred at a medium-sized city in the Northeast Region of Brazil in 2009, we conducted an ecological study of the notified dengue cases georeferenced according to epidemiological week (EW) and home address. Kernel density estimation and space-time interaction were analysed using the Knox method. The evolution of the epidemic was analysed using an animated projection technique. The dengue incidence was 6.918.7/100,000 inhabitants; the peak of the epidemic occurred from 8 February-1 March, EWs 6-9 (828.7/100,000 inhabitants). There were cases throughout the city and was identified space-time interaction. Three epicenters were responsible for spreading the disease in an expansion and relocation diffusion pattern. If the health services could detect in real time the epicenters and apply nimbly control measures, may possibly reduce the magnitude of dengue epidemics.

Temporal abundance of Aedes aegypti in Manaus, Brazil, measured by two trap types for adult mosquitoes

A longitudinal study was conducted in Manaus, Brazil, to monitor changes of adult Aedes aegypti (L.) abundance. The objectives were to compare mosquito collections of two trap types, to characterise temporal changes of the mosquito population, to investigate the influence of meteorological variables on mosquito collections and to analyse the association between mosquito collections and dengue incidence. Mosquito monitoring was performed fortnightly using MosquiTRAPs (MQT) and BG-Sentinel (BGS) traps between December 2008-June 2010. The two traps revealed opposing temporal infestation patterns, with highest mosquito collections of MQTs during the dry season and highest collections of BGS during the rainy seasons. Several meteorological variables were significant predictors of mosquito collections in the BGS. The best predictor was the relative humidity, lagged two weeks (in a positive relationship). For MQT, only the number of rainy days in the previous week was significant (in a negative relationship). The correlation between monthly dengue incidence and mosquito abundance in BGS and MQT was moderately positive and negative, respectively. Catches of BGS traps reflected better the dynamic of dengue incidence. The findings help to understand the effects of meteorological variables on mosquito infestation indices of two different traps for adult dengue vectors in Manaus.

Dengue: clinical forms and risk groups in a high incidence city in the southeastern region of Brazil

INTRODUCTION: The article describes the epidemiologic profile of dengue cases in Vitória, the capital of Espírito Santo, Brazil, from 2000 to 2009, aimed at identifying risk groups regarding the incidence and severity of the disease. METHODS: Confirmed cases of dengue among city residents during ten years were classified as dengue fever, dengue hemorrhagic fever, dengue shock syndrome and dengue with complications, and analyzed according to sex, age, race-color and education. RESULTS: The proportion of dengue cases was highest among women aged 20 to 29 years-old and similar between whites and blacks. A gradual decrease occurred in the percentage of dengue cases in the population aged 15 years-old or more, in the historical series of 10 years, and a growing increase in individuals less than 15 years-old, showing statistical significance. The fatality rate ranged from zero to 0.3% for all forms of dengue and from 0.2% to 18.2% for severe forms. CONCLUSIONS: The profile of those affected by the disease in the municipality is similar to those affected in Brazil. The increasing number of cases in individuals under 15 years-old corroborates the results of recent studies in other Brazilian municipalities.

DENGUE OUTBREAK IN MATO GROSSO STATE, MIDWESTERN BRAZIL

Dengue virus (DENV) is the most frequent arbovirus worldwide. In this study, we report a large outbreak in Mato Grosso State (MT). Serum samples from 604 patients with acute febrile illness for less than five days were inoculated in C6/36 cells, then infected cells were subjected to an indirect immunofluorescence test for DENV serotypes and yellow fever virus. Serum samples were submitted to a multiplex-semi-nested-RT-PCR for 11 flaviviruses. DENV-4 was isolated in 150/604 (24.8%) and DENV-1 in 19/604 (3.1%) specimens. By RT-PCR, 331 (54.8%) samples tested positive for DENV; 321 had single infections (DENV-4 n = 305; DENV-1 n = 15; DENV-3 n = 1), nine had co-infections of DENV-1/DENV-4, and one of DENV-2/DENV-4. DENV-4 was detected in 315/331 (95.2%) positive patients from 17 municipalities, and DENV-1 in 24/331 (7.2%) patients from five cities in north-central MT and the city of Cuiaba. The incidence of infection was higher in patients aged 20-39 (142/331; 42.9%). The NS5 partial nucleotide sequence of DENV-1 was most similar to that of genotype V, DENV-2 to Southeast Asian/American, DENV-3 to genotype III, and DENV-4 to genotype II strains, considered the most frequent strains in Brazil. This outbreak coincided with the introduction of DENV-4 in the state. Cuiaba was hyperendemic for the four DENV serotypes, highlighting the necessity for arbovirus surveillance in MT.

Dengue and dengue hemorrhagic fever in the State of Pernambuco, 1995-2006

In Pernambuco, the first dengue cases occurred in 1987. After a seven-year interval without autochthonous cases, a new epidemic occurred in 1995. Important aspects of the dengue epidemics during the period 1995-2006 have been analyzed here, using epidemiological, clinical and laboratory data. A total of 378,374 cases were notified, with 612 confirmed cases of dengue hemorrhagic fever and 33 deaths. The mortality rate was 5.4%. The incidence rate increased from 134 to 1,438/100,000 inhabitants, corresponding to the epidemics due to serotypes 2 and 3, in 1995 and 2002, respectively. Dengue mainly affected adults (20-49 years); 40.7% were male and 59.3% were female. From 2003 onwards, the number of cases among individuals younger than 15 years old increased. Out of 225 dengue hemorrhagic fever cases, 42.7% primary and 57.3% secondary infections were identified (p = 0.0279). Neurological manifestations were also observed. From 2002 onwards, serotypes 1, 2 and 3 were circulating; serotype 3 was predominant.

Epidemiological aspects of dengue in Aracaju, State of Sergipe, Brazil

INTRODUCTION: The dengue fever remains to be a disease of serious public health concern, and its incidence has increased in the past decades. This study aimed to characterize the epidemiological incidence of dengue in the period 2001-2010. METHODS: This is an epidemiological study of dengue in the municipality of Aracaju, state of Sergipe, in the period between 2001 and 2010, whose data were obtained from the Information System of Diseases Notifications. A descriptive analysis of the number of confirmed cases of dengue, according to year, semester, sanitary district, age, and sex, was performed. RESULTS: There were 16,462 confirmed cases, especially in 2008, which obtained the highest incidence of the disease, with 10,485 confirmed cases. The first semester obtained the highest registration of cases during the years of research; this was predominated by females between 15 and 49 years old. With regard to the territorial distribution, the second district of the municipality obtained the highest number of cases. CONCLUSIONS: In 2008, in the City of Aracaju, SE, a significant increase in the proportion of dengue cases compared with other years was verified. However, a fast decline in the other years was observed, possibly because of the intensification of preventive actions to combat the mosquito that transmits the dengue virus.

Occurrence of severe dengue in Rio de Janeiro: an ecological study

Introduction This study aimed to analyze the relationship between the incidence of severe dengue during the 2008 epidemic in Rio de Janeiro, Brazil, and socioeconomic indicators, as well as indicators of health service availability and previous circulation of the dengue virus serotype-3 (DENV-3). Methods In this ecological study, the units of analysis were the districts of Rio de Janeiro. The data were incorporated into generalized linear models, and the incidence of severe dengue in each district was the outcome variable. Results The districts with more cases of dengue fever in the 2001 epidemic and a higher percentage of residents who declared their skin color or race as black had higher incidence rates of severe dengue in the 2008 epidemic [incidence rate ratio (IRR)= 1.21; 95% confidence interval (95%CI)= 1.05-1.40 and IRR= 1.34; 95%CI= 1.16-1.54, respectively]. In contrast, the districts with Family Health Strategy (FHS) clinics were more likely to have lower incidence rates of severe dengue in the 2008 epidemic (IRR= 0.81; 95%CI= 0.70-0.93). Conclusions At the ecological level, our findings suggest the persistence of health inequalities in this region of Brazil that are possibly due to greater social vulnerability among the self-declared black population. Additionally, the protective effect of FHS clinics may be due to the ease of access to other levels of care in the health system or to a reduced vulnerability to dengue transmission that is afforded by local practices to promote health.

Study of the relationship between Aedes (Stegomyia) aegypti egg and adult densities, dengue fever and climate in Mirassol, state of São Paulo, Brazil

The purpose of this study was to examine the relationship between Aedes aegypti egg and adult density indices, dengue fever and climate in Mirassol, state of São Paulo, Brazil, between November 2004-November 2005. Weekly collections of adults and eggs were made using, respectively, manual aspirators and oviposition traps that produced four entomological indices (positivity and average of females and eggs). Weekly incidence coefficients were calculated based on dengue cases. Each week, the data obtained from entomological indices were related to each other, dengue, and climate variables. The first index to show an association with dengue transmission was the female average, followed by female positivity and egg average. Egg positivity did not show a relationship with risk for dengue, but was sensitive to identifying the presence of the vector, principally in dry seasons. The relationship between climatic factors, the vector and the disease found in this study can be widely employed in planning and undertaking dengue surveillance and control activities, but it is a tool that has not been considered by the authorities responsible for controlling the disease. In fact, this relationship permits the use of information about climate for early detection of epidemics and for establishing more effective prevention strategies than currently exist.

Proportional cancer incidence according to selected sites: comparison between residents in the City of S. Paulo, Brazil: Japanese and Brazilian/Portuguese descent

The percentual distributions of selected sites of cancer cases according to origin, sex and age are compared. Data were obtained from the Registry of Cancer of S. Paulo (School of Public Health of the University of S. Paulo, Brazil). The reference period for inhabitants of Japanese descent was 1969/78 and for those of Brazilian descent, the period was 1969/75. Standardized Proportionate Incidence Ratios (SPIR) with approximate 95% Confidence Intervals (CI) were evaluated using age specific Incidence Ratios of S. Paulo, 1973, as standards. The results agree with findings of previous works on mortality, but show different patterns according to origin. The well known fact that some sub-groups of a population may be different from the overall group is once again brought to the fore. Attention should be drawn to the differences detected for stomach, skin and prostate, in males, and for stomach, skin, cervix and uterus in females.

Epidemia de dengue em Ribeirão Preto, SP, Brasil: nota prévia

Apresenta-se Nota preliminar de uma epidemia de dengue, ocorrida em Ribeirão Preto, São Paulo, Brasil, no período de novembro de 1990 a março de 1991. Descreve-se a ocorrência de um caso de "Dengue Hemorrhagic Fever/Dengue Shock Syndrome" Grau II (DHF/DSS) e de dois óbitos associados ao dengue devido a síndrome de choque. Alerta clínicos e epidemiologistas quanto à possibilidade de ocorrência de casos isolados de DHF/DSS durante epidemias de dengue clássico em áreas antes indenes à doença.

Dengue in the South-eastern region of Brazil: historical analysis and epidemiology

The aim of the study is an historical analysis of the work undertaken by the Public Health organizations dedicated to the combat of the Aedes aegypti, as well as an epidemiolocal study of persons with unexplained fever, with a view to evaluating the ocurrence of dengue within the population. The Mac-Elisa, Gac-Elisa, hemaglutination inhibition, isolation and typage tests were used. Organophosphate intoxication in agricultural workers was also assessed by measuring concentrations of serie cholinesterase. A sera samples of 2,094 were collected in 23 towns, and the type 1 dengue virus was detected in 17 towns and autochthony was confirmed in 12 of them. The cholinesterase was measured in 2,391 sera samples of which 53 cases had abnormal levels. Poisoning was confirmed in 3 cases. Results reveal an epidemic the gravity of which was not officially know. The relationshipe between levels of IgM and IgG antibodies indicates the outbreak tendency. The widespread distribution of the vector is troubling because of the possibility of the urbanization of wild yellow fever, whereas the absence of A. aegypti in 2 towns with autochthony suggests the existence of another vector. Since there is no vaccine against dengue, the combat of the vector is the most efficient measure for preventing outbreaks. The eradication of the vector depends on government decisions which depend, for their execution, on the organization of the Health System and the propagation of information concerning the prevention of the disease using all possible means because short and long term results depend on the education and the active participation of the entire population.

Estudo comparativo de eficácia de larvitrampas e ovitrampas para vigilância de vetores de dengue e febre amarela

Com a finalidade de aprimorar a vigilância entomológica dos vetores de Dengue e Febre Amarela - Aedes aegypti e Aedes albopictus - no Estado de São Paulo, Brasil, realizou-se estudo comparativo de eficácia de larvitrampas (armadilhas de larvas), e ovitrampas (armadilhas de ovos). A região estudada é infestada somente pelo Aedes albopictus, espécie que conserva hábitos silvestres, mas também coloniza criadouros artificiais. A primeira parte do estudo foi realizada em área periurbana de Tremembé-SP, onde foram comparados três ocos de árvore, 23 ovitrampas e 5 larvitrampas. A segunda parte dos experimentos desenvolveu-se no Município de Lavrinhas-SP, no distrito de Pinheiros, onde 20 ovitrampas foram instaladas (uma por quadra) e 5 larvitrampas foram localizadas em pontos estratégicos (comércios, depósitos e postos). Os resultados obtidos mostraram que a ovitrampa, além da capacidade de positivar-se mesmo em presença de criadouros naturais, possui eficiência superior à larvitrampa. Constatou-se que para avaliação de efeitos da termonebulização as ovitrampas apresentaram uma significativa redução na média de ovos, o que não se verificou em relação ao Índice de Breteau.