Identification of Hazard and Socio-Demographic Patterns of Dengue Infections in a Colombian Subtropical Region from 2015 to 2020: Cox Regression Models and Statistical Analysis.

Dengue is a disease of high interest for public health in the affected localities. Dengue virus is transmitted by Aedes species and presents hyperendemic behaviors in tropical and subtropical regions. Colombia is one of the countries most affected by the dengue virus in the Americas. Its central-west region is a hot spot in dengue transmission, especially the Department of Antioquia, which has suffered from multiple dengue outbreaks in recent years (2015-2016 and 2019-2020). In this article, we perform a retrospective analysis of the confirmed dengue cases in Antioquia, discriminating by both subregions and dengue severity from 2015 to 2020. First, we conduct an exploratory analysis of the epidemic data, and then a statistical survival analysis is carried out using a Cox regression model. Our findings allow the identification of the hazard and socio-demographic patterns of dengue infections in the Colombian subtropical region of Antioquia from 2015 to 2020.

Dexamethasone vs methylprednisolone high dose for Covid-19 pneumonia.

BACKGROUND: There is no effective therapy for the severe acute respiratory syndrome by coronavirus 2 (SARS-CoV2) responsible for the Coronavirus disease 2019 (Covid-19). To date, dexamethasone has shown a decrease in mortality in patients who require oxygen, especially those with invasive mechanical ventilation. However, it is unknown if another corticosteroid can be used, the optimal dose and its duration, to achieve a better clinical outcome. The objective of the study was to compare the differences in clinical outcome and laboratory results in hospitalized patients with severe SARS-CoV2 Pneumonia treated with dexamethasone at 6 mg doses versus patients treated with high-dose methylprednisolone. MATERIALS AND METHODS: Ambispective cohort study with survival analysis of 216 patients diagnosed with severe Covid-19 pneumonia confirmed by polymerase chain reaction for SARS-CoV2 by Berlin protocol, who were hospitalized in a high-complexity clinic in Medellín, Colombia. The patients should also have supplementary oxygen and radiological confirmation of Pneumonia by chest tomography. Sample size was not calculated since the total population that met the inclusion criteria was evaluated. 111 patients were treated with the institutional protocol with intravenous dexamethasone 6 mg QD for seven to 10 days if they required oxygen. Since September 15, 2020, the hospitalization protocol of the clinic was modified by the Infectious Diseases and Pulmonology service, recommending a high dose of methylprednisolone of 250 to 500 mg every day for three days with a subsequent change to oral prednisone 50 mg every day for 14 days. The protocol was not applied in the intensive care unit, where dexamethasone continued to be administered. The clinical outcome and differences in laboratory results of the patients who received dexamethasone vs. the prospective cohort that received methylprednisolone from September 15 to October 31, 2020, were evaluated. Follow-up was carried out by outpatient consultation one month after discharge or by telephone, inquiring about readmission or living-dead status. RESULTS: 216 patients had Covid-19 pneumonia documented by ground-glass imaging and alveolar pressure / inspired oxygen fraction (PaFi) less than 300. 111 patients received dexamethasone (DXM) and 105 received methylprednisolone (MTP). Patients in the DXM group evolved to severe ARDS in a higher proportion (26.1% vs 17.1% than the MTP group). Upon completion 4 days of treatment with parenteral corticosteroid, laboratory markers of severity decreased significantly in the group that received MTP, CRP 2.85 (2.3-3.8) vs 7.2 (5.4-9.8), (p-value < 0.0001), D-dimer 691 (612-847) vs 1083 (740-1565) (p-value = 0.04) and DHL 273 (244-289) vs 355 (270.6-422) (p-value = 0.01). After starting the corticosteroid, transfer to the intensive care unit (4.8% vs. 14.4%) and mortality (9,5% vs. 17.1%) was lower in the group that received MTP. Recovery time was shorter in patients treated with MTP, three days (3-4) vs. DXM 6 days (5-8) (p-value < 0.0001). At 30-day follow-up, 88 (92.6%) were alive in MTP vs 58 (63.1%) of those who received dexamethasone. CONCLUSIONS: In this study, the treatment of severe Covid-19 Pneumonia with high-dose methylprednisolone for three days followed by oral prednisone for 14 days, compared with 6 mg dexamethasone for 7 to 10 days, statistically significantly decreased the recovery time, the need for transfer to intensive care and the severity markers C-reactive protein (CRP), D-dimer and LDH. Randomized controlled studies with methylprednisolone are required to corroborate its effect, and studies in a population hospitalized in intensive care wards.

An alternative model to explain the vectorial capacity using as example Aedes aegypti case in dengue transmission.

Vectorial capacity (VC), as a concept that describes the potential of a vector to transmit a pathogen, has had historical problems related to lacks in dimensional significance and high error propagation from parameters that take part in the model to output. Hence, values estimated with those equations are not sufficiently reliable to consider in control strategies or vector population study. In this paper, we propose a new VC model consistent at dimensional level, i.e., the definition and the equation of VC have same and consistent units, with a parameter estimation method and mathematical structure that reduces the uncertainty in model output, using as a case of study an Aedes aegypti population of the municipality of Bello, Colombia. After a literature review, we selected one VC equation following biological, measurability and dimensional criteria, then we rendered a local and global sensitivity analysis, identifying the mortality rate of mosquitoes as a target component of the equation. Thus, we studied the Weibull and Exponential distributions as probabilistic models that represent the expectation of mosquitoes infective life, intending to include the best distribution in a selected VC structure. The proposed mortality rate estimation method includes a new parameter that represents an increase or decrease in vector mortality, as it may apply. We noticed that its estimation reduces the uncertainty associated with the expectation of mosquitoes' infective life expression, which also reduces the output range and variance in almost a half.

S-maup: Statistical test to measure the sensitivity to the modifiable areal unit problem.

This work presents a nonparametric statistical test, S-maup, to measure the sensitivity of a spatially intensive variable to the effects of the Modifiable Areal Unit Problem (MAUP). To the best of our knowledge, S-maup is the first statistic of its type and focuses on determining how much the distribution of the variable, at its highest level of spatial disaggregation, will change when it is spatially aggregated. Through a computational experiment, we obtain the basis for the design of the statistical test under the null hypothesis of non-sensitivity to MAUP. We performed an exhaustive simulation study for approaching the empirical distribution of the statistical test, obtaining its critical values, and computing its power and size. The results indicate that, in general, both the statistical size and power improve with increasing sample size. Finally, for illustrative purposes, an empirical application is made using the Mincer equation in South Africa, where starting from 206 municipalities, the S-maup statistic is used to find the maximum level of spatial aggregation that avoids the negative consequences of the MAUP.