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Abstract Background Vector control programs, which have focused mainly on the patient house and peridomestic areas around dengue cases, have not produced the expected impact on transmission. This project will evaluate the assumption that the endemic/epidemic transmission of dengue begins around peridomestic vicinities of the primary cases. Its objective is to assess the relationship between symptomatic dengue case exposure and peridomestic infection incidence. Methods/Design A prospective cohort study will be conducted (in Tepalcingo and Axochiapan, in the state of Morelos, Mexico), using the state surveillance system for the detection of incident cases. Paired blood specimens will be collected from both the individuals who live with the incident cases and a sample of subjects residing within a 25-meter radius of such cases (exposed cohort), in order to measure dengue-specific antibodies. Other subjects will be selected from areas which have not presented any incident cases within 200 meters, during the two months preceding the sampling (non-exposed cohort). Symptomatic/asymptomatic incident infection will be considered as the dependent variable, exposure to confirmed dengue cases, as the principal variable, and the socio-demographic, environmental and socio-cultural conditions of the subjects, as additional explanatory variables. Discussion Results indicating a high infection rate among the exposed subjects would justify the application of peridomestic control measures and call for an evaluation of alternate causes for insufficient program impact. On the other hand, a low incidence of peridomestic-infected subjects would support the hypothesis that infection occurs outside the domicile, and would thus explain why the vector control measures applied in the past have exerted such a limited impact on cases incidence rates. The results of the present study may therefore serve to reassess site selection for interventions of this type.

Abstract Background Odds ratios (OR) significantly overestimate associations between risk factors and common outcomes. The estimation of relative risks (RR) or prevalence ratios (PR) has represented a statistical challenge in multivariate analysis and, furthermore, some researchers do not have access to the available methods. Objective: To propose and evaluate a new method for estimating RR and PR by logistic regression. Methods A provisional database was designed in which events were duplicated but identified as non-events. After, a logistic regression was performed and effect measures were calculated, which were considered RR estimations. This method was compared with binomial regression, Cox regression with robust variance and ordinary logistic regression in analyses with three outcomes of different frequencies. Results ORs estimated by ordinary logistic regression progressively overestimated RRs as the outcome frequency increased. RRs estimated by Cox regression and the method proposed in this article were similar to those estimated by binomial regression for every outcome. However, confidence intervals were wider with the proposed method. Conclusion This simple tool could be useful for calculating the effect of risk factors and the impact of health interventions in developing countries when other statistical strategies are not available.

We aimed to assess clinical and laboratory differences between dengue and chikungunya in children <24 months of age in a comparative study. We collected retrospective clinical and laboratory data confirmed by NS1/IgM for dengue for 19 months (1 January 2013 to 17 August 2014). Prospective data for chikungunya confirmed by real-time polymerase chain reaction were collected for 4 months (22 September 2014-14 December 2014). Sensitivity and specificity [with 95% confidence interval (CI)] were reported for each disease diagnosis. A platelet count <150 000 cells/ml at emergency admission best characterized dengue, with a sensitivity of 67% (95% CI, 53-79) and specificity of 95% (95% CI, 82-99). The algorithm developed with classification and regression tree analysis showed a sensitivity of 93% (95% CI, 68-100) and specificity of 38% (95% CI, 9-76) to diagnose dengue. Our study provides potential differential characteristics between chikungunya and dengue in young children, especially low platelet counts., (© The Author [2017]. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Introduction: Spontaneous haemorrhage is an important cause of hospitalisation in dengue patients. Early predictors of these complications could help to make opportune decisions., Methods: We prospectively evaluated 51 febrile patients (without previous spontaneous haemorrhage), including 32 cases of dengue fever. Initial evaluation was performed during the first 96 hours after the onset of fever and included complete blood cell count and coagulation tests. Participants were followed-up daily until the seventh day of the disease., Results: Overall, 15 patients developed spontaneous haemorrhage during the follow-up. Tourniquet test and dengue infection were not associated with haemorrhage (p-value is greater than 0.2). In a logistic regression analysis, platelet count (odds-ratio [OR] 0.78; 95 percent confidence interval [CI] 0.65-0.94) and partial thromboplastin time (OR 1.78; 95 percent CI 1.06-2.99) were independently associated with spontaneous haemorrhage., Conclusion: Early alterations in platelet count and coagulation test could predict spontaneous bleeding in the acute febrile syndrome.

Objective: Describing patterns of acute febrile syndrome (AFS) consultation related to dengue and evaluating association with rainfall., Methods: 318 undifferentiated AFS patients were detected in two clinics during a 7-month period (March to September) and then included in systematic clinical follow-up. 31 % of them (81/281) were IgM positive for dengue. Rainfall (litres/square meter-day) during the previous weeks was evaluated as a variable for predicting consultation patterns., Results: June, July and September were the months in which the greatest number of AFS cases occurred. Cases of dengue were only significantly more frequent during July. When evaluating the previous weeks' rainfall patterns, consultation for AFS was seen to be associated with the average rainfall registered 5 weeks beforehand and such association was independent of the institution and/or month (incidence rate ratio IRR=1,04; 1-1.08 95 %CI, p=0.045). On the other hand, 5 consecutive weeks' average rainfall was an independent predictor of consultation for dengue 4 weeks later on (RTI=1 ,6 ; 1,15-2,22 95 %CI, p=0.006). A linear relationship was thus proposed (regarding these sentinel clinics) between consultation for dengue and rainfall: lt/mt-day (5 weeks' average rainfall) X 0 ,72 (0,60-0,84 95 %CI, p<0.001) = cases for each 100 000 habitants per week (4 weeks later)., Conclusions: Studying rainfall could predict the pattern of consultation for dengue in endemic regions.

Objective: To identify clinical manifestations and laboratory findings useful for the early diagnosis of dengue in children., Materials and Methods: We prospectively evaluated 125 children (aged 5 to 12 years old) with acute febrile syndrome with no apparent etiology. Paired serologic tests and/or viral culture were performed and dengue infection was confirmed in 40 patients and ruled out in 68 (17 indefinite cases). Early clinical manifestations (within the first 4 days of the disease) in the groups with dengue and other causes of febrile syndrome were compared. Independent indicators of dengue were determined in a multivariate logistic regression analysis., Results: When clinical manifestations and complete blood count were considered, the independent indicators of dengue were: absence of nasal discharge, facial flushing, and leukocyte count < or = 4,500/.l. With at least two of these findings, a sensitivity of 67 % and a specificity of 72 % for the diagnosis of dengue were obtained. When coagulation tests were considered, a model for diagnosis was composed of: absence of nasal discharge, leukocyte count < or = 4500/.l, prothrombin time > 14 seconds, and partial thromboplastin time > 29 seconds. Two of these findings suggested a diagnosis of dengue with a sensitivity of 90 % and a specificity of 52.9 %. With at least 3 findings, specificity increased to 89.7 % and sensitivity decreased to 50 %. The presence of the four components of this latter model shows a specificity of 100 %., Conclusions: Some clinical manifestations and simple laboratory tests could aid the early detection of dengue infection in children.

Evaluation of IgM determination in acute serum for the diagnosis of dengue in an endemic area We evaluated the clinical usefulness of dengue IgM detection in acute serum using an ELISA test in 167 patients with dengue and 225 patients with acute febrile syndrome of another etiology. The sensitivity of the test was 29.9%, specificity was 99.1%, positive predictive value was 96.2%, and negative predictive value was 65.6%. Because of the test's high specificity and positive predictive value, a positive result could support a diagnosis of dengue in endemic areas with a high degree of certainty; a negative result would require complementary studies.