Modeling spillover dynamics: understanding emerging pathogens of public health concern.

The emergence of infectious diseases with pandemic potential is a major public health threat worldwide. The World Health Organization reports that about 60% of emerging infectious diseases are zoonoses, originating from spillover events. Although the mechanisms behind spillover events remain unclear, mathematical modeling offers a way to understand the intricate interactions among pathogens, wildlife, humans, and their shared environment. Aiming at gaining insights into the dynamics of spillover events and the outcome of an eventual disease outbreak in a population, we propose a continuous time stochastic modeling framework. This framework links the dynamics of animal reservoirs and human hosts to simulate cross-species disease transmission. We conduct a thorough analysis of the model followed by numerical experiments that explore various spillover scenarios. The results suggest that although most epidemic outbreaks caused by novel zoonotic pathogens do not persist in the human population, the rising number of spillover events can avoid long-lasting extinction and lead to unexpected large outbreaks. Hence, global efforts to reduce the impacts of emerging diseases should not only address post-emergence outbreak control but also need to prevent pandemics before they are established.

Beyond Conventional Carbon Activation: Creating Porosity without Etching Using Cesium Effect.

Facile synthesis of porous carbon with high yield and high specific surface area (SSA) from low-cost molecular precursors offers promising opportunities for their industrial applications. However, conventional activation methods using potassium and sodium hydroxides or carbonates suffer from low yields (<20%) and poor control over porosity and composition especially when high SSAs are targeted (>2000 m2 g-1) because nanopores are typically created by etching. Herein, a non-etching activation strategy is demonstrated using cesium salts of low-cost carboxylic acids as the sole precursor in producing porous carbons with yields of up to 25% and SSAs reaching 3008 m2 g-1. The pore size and oxygen content can be adjusted by tuning the synthesis temperature or changing the molecular precursor. Mechanistic investigation unravels the non-classical role of cesium as an activating agent. The cesium compounds that form in situ, including carbonates, oxides, and metallic cesium, have extremely low work function enabling electron injection into organic/carbonaceous framework, promoting condensation, and intercalation of cesium ions into graphitic stacks forming slit pores. The resulting porous carbons deliver a high capacity of 252 mAh g-1 (567 F g-1) and durability of 100 000 cycles as cathodes of Zn-ion capacitors, showing their potential for electrochemical energy storage.

Optimal vaccination strategies for a heterogeneous population using multiple objectives: The case of L1- and L2-formulations.

The choice of the objective functional in optimization problems coming from biomedical and epidemiological applications plays a key role in optimal control outcomes. In this study, we investigate the role of the objective functional on the structure of the optimal control solution for an epidemic model for sexually transmitted infections that includes a core group with higher sexual activity levels than the rest of the population. An optimal control problem is formulated to find a targeted vaccination program able to control the spread of the infection with minimum vaccine deployment. Both L1- and L2-objectives are considered as an attempt to explore the trade-offs between control dynamics and the functional form characterizing optimality. The results show that the optimal vaccination policies for both the L1- and the L2-formulation share one important qualitative property, that is, immunization of the core group should be prioritized by policymakers to achieve a fast reduction of the epidemic. However, quantitative aspects of this result can be significantly affected depending on the choice of the control weights between formulations. Overall, the results suggest that with appropriate weight constants, the optimal control outcomes are reasonably robust with respect to the L1- or L2-formulation. This is particularly true when the monetary cost of the control policy is substantially lower than the cost associated with the disease burden. Under these conditions, even if the L1-formulation is more realistic from a modeling perspective, the L2-formulation can be used as an approximation and yield qualitatively comparable outcomes.

Data-driven estimation of the instantaneous reproduction number and growth rates for the 2022 monkeypox outbreak in Europe.

OBJECTIVE: To estimate the instantaneous reproduction number Rt and the epidemic growth rates for the 2022 monkeypox outbreaks in the European region. METHODS: We gathered daily laboratory-confirmed monkeypox cases in the most affected European countries from the beginning of the outbreak to September 23, 2022. A data-driven estimation of the instantaneous reproduction number is obtained using a novel filtering type Bayesian inference. A phenomenological growth model coupled with a Bayesian sequential approach to update forecasts over time is used to obtain time-dependent growth rates in several countries. RESULTS: The instantaneous reproduction number Rt for the laboratory-confirmed monkeypox cases in Spain, France, Germany, the UK, the Netherlands, Portugal, and Italy. At the early phase of the outbreak, our estimation for Rt, which can be used as a proxy for the basic reproduction number R0, was 2.06 (95% CI 1.63 - 2.54) for Spain, 2.62 (95% CI 2.23 - 3.17) for France, 2.81 (95% CI 2.51 - 3.09) for Germany, 1.82 (95% CI 1.52 - 2.18) for the UK, 2.84 (95% CI 2.07 - 3.91) for the Netherlands, 1.13 (95% CI 0.99 - 1.32) for Portugal, 3.06 (95% CI 2.48 - 3.62) for Italy. Cumulative cases for these countries present subexponential rather than exponential growth dynamics. CONCLUSIONS: Our findings suggest that the current monkeypox outbreaks present limited transmission chains of human-to-human secondary infection so the possibility of a huge pandemic is very low. Confirmed monkeypox cases are decreasing significantly in the European region, the decline might be attributed to public health interventions and behavioral changes in the population due to increased risk perception. Nevertheless, further strategies toward elimination are essential to avoid the subsequent evolution of the monkeypox virus that can result in new outbreaks.

Heterostructured Cobalt Silicide Nanocrystals: Synthesis in Molten Salts, Ferromagnetism, and Electrocatalysis.

Nanoscale heterostructures of covalent intermetallics should give birth to a wide range of interface-driven physical and chemical properties. Such a level of design however remains unattainable for most of these compounds, due to the difficulty to reach a crystalline order of covalent bonds at the moderate temperatures required for colloidal chemistry. Herein, we design heterostructured cobalt silicide nanoparticles to trigger magnetic and catalytic properties in silicon-based materials. Our strategy consists in controlling the diffusion of cobalt atoms into silicon nanoparticles, by reacting these particles in molten salts. By adjusting the temperature, we tune the conversion of the initial silicon particles toward homogeneous CoSi nanoparticles and core-shell nanoparticles made of a CoSi shell and a silicon-rich core. The increased interface-to-volume ratio of the CoSi component in the core-shell particles yields distinct properties compared to the bulk and homogeneous nanoparticles. First, the core-shell particles exhibit increased ferromagnetism, despite the bulk diamagnetic properties of cobalt monosilicide. Second, the core-shell nanoparticles act as efficient precatalysts for alkaline water oxidation, where the nanostructure is converted in situ into a layered cobalt silicon oxide/(oxy)hydroxide with high and stable oxygen evolution reaction (OER) electrocatalytic activity. This work demonstrates a route to design heterostructured nanocrystals of covalent intermetallic compounds and shows that these new structures exhibit very rich, yet poorly explored, interface-based physical properties and reactivity.

Optimal vaccine allocation for the control of sexually transmitted infections.

The burden of sexually transmitted infections (STIs) poses a challenge due to its large negative impact on sexual and reproductive health worldwide. Besides simple prevention measures and available treatment efforts, prophylactic vaccination is a powerful tool for controlling some viral STIs and their associated diseases. Here, we investigate how prophylactic vaccines are best distributed to prevent and control STIs. We consider sex-specific differences in susceptibility to infection, as well as disease severity outcomes. Different vaccination strategies are compared assuming distinct budget constraints that mimic a scarce vaccine stockpile. Vaccination strategies are obtained as solutions to an optimal control problem subject to a two-sex Kermack-McKendrick-type model, where the control variables are the daily vaccination rates for females and males. One important aspect of our approach relies on conceptualizing a limited but specific vaccine stockpile via an isoperimetric constraint. We solve the optimal control problem via Pontryagin's Maximum Principle and obtain a numerical approximation for the solution using a modified version of the forward-backward sweep method that handles the isoperimetric budget constraint in our formulation. The results suggest that for a limited vaccine supply ([Formula: see text]-[Formula: see text] vaccination coverage), one-sex vaccination, prioritizing females, appears to be more beneficial than the inclusion of both sexes into the vaccination program. Whereas, if the vaccine supply is relatively large (enough to reach at least [Formula: see text] coverage), vaccinating both sexes, with a slightly higher rate for females, is optimal and provides an effective and faster approach to reducing the prevalence of the infection.

Revealing the Elusive Structure and Reactivity of Iron Boride α-FeB.

Crystal structures can strongly deviate from bulk states when confined into nanodomains. These deviations may deeply affect properties and reactivity and then call for a close examination. In this work, we address the case where extended crystal defects spread through a whole solid and then yield an aperiodic structure and specific reactivity. We focus on iron boride, α-FeB, whose structure has not been elucidated yet, thus hindering the understanding of its properties. We synthesize the two known phases, α-FeB and ß-FeB, in molten salts at 600 and 1100 °C, respectively. The experimental X-ray diffraction (XRD) data cannot be satisfactorily accounted for by a periodic crystal structure. We then model the compound as a stochastic assembly of layers of two structure types. Refinement of the powder XRD pattern by considering the explicit scattering interference of the different layers allows quantitative evaluation of the size of these domains and of the stacking faults between them. We, therefore, demonstrate that α-FeB is an intergrowth of nanometer-thick slabs of two structure types, ß-FeB and CrB-type structures, in similar proportions. We finally discuss the implications of this novel structure on the reactivity of the material and its ability to perform insertion reactions by comparing the reactivities of α-FeB and ß-FeB as reagents in the synthesis of a model layered material: Fe2AlB2. Using synchrotron-based in situ X-ray diffraction, we elucidate the mechanisms of the formation of Fe2AlB2. We highlight the higher reactivity of the intergrowth α-FeB in agreement with structural relationships.

The trade-off between mobility and vaccination for COVID-19 control: a metapopulation modelling approach.

November 2020 received a string of encouraging results from leading vaccine developers raising hopes for the imminent availability of an effective and safe vaccine against the SARS-CoV-2. In the present work, we discuss the theoretical impact of introducing a vaccine across a range of scenarios. In particular, we investigate how vaccination coverage, efficacy and delivery time affect the control of the transmission dynamics in comparison to mobility restrictions. The analysis is based on a metapopulation epidemic model structured by risk. We perform a global sensitivity analysis using the Sobol method. Our analysis suggest that the reduction of mobility among patches plays a significant role in the mitigation of the disease close to the effect of immunization coverage of 30% achieved in four months. Moreover, for an immunization coverage between 20% and 50% achieved in the first half of 2021 with a vaccine efficacy between 70% and 95%, the percentage reduction in the total number of SARS-CoV-2 infections is between 30% and 50% by the end of 2021 in comparison with the no vaccination scenario.

Modeling the transmission dynamics and the impact of the control interventions for the COVID-19 epidemic outbreak.

In this paper we develop a compartmental epidemic model to study the transmission dynamics of the COVID-19 epidemic outbreak, with Mexico as a practical example. In particular, we evaluate the theoretical impact of plausible control interventions such as home quarantine, social distancing, cautious behavior and other self-imposed measures. We also investigate the impact of environmental cleaning and disinfection, and government-imposed isolation of infected individuals. We use a Bayesian approach and officially published data to estimate some of the model parameters, including the basic reproduction number. Our findings suggest that social distancing and quarantine are the winning strategies to reduce the impact of the outbreak. Environmental cleaning can also be relevant, but its cost and effort required to bring the maximum of the outbreak under control indicate that its cost-efficacy is low.

Modeling Public Health Campaigns for Sexually Transmitted Infections via Optimal and Feedback Control.

Control of sexually transmitted infections (STIs) poses important challenges to public health authorities. Obstacles for STIs' control include low priority in public health programs and disease transmission mechanisms. This work uses a compartmental pair model to explore different public health strategies on the evolution of STIs. Optimal control and feedback control are used to model realistic strategies for reducing the prevalence of these infections. Feedback control is proposed to model the reaction of public health authorities relative to an alert level. Optimal control is used to model the optimization of available resources for implementing strategies. Numerical simulations are performed using trichomoniasis, gonorrhea, chlamydia and human papillomavirus (HPV) as study cases. HPV is non-curable, and it is analyzed only under transmission control such as condom promotion campaigns. Trichomoniasis, gonorrhea and chlamydia are curable STIs that are modeled here additionally under treatment control. Increased cost-effectiveness ratio is employed as a criterion to measure control strategies performance. The features and drawbacks of control strategies under the pair formation process are discussed.

The role of behavioral changes and prompt treatment in the control of STIs.

In this paper, we study general recovery functions and treatment in the dynamics of an S I S model for sexually transmitted infections with nonzero partnership length. It is shown how partnership dynamics influences the predicted prevalence at the steady state and the basic reproduction number. Sobol's indices are used to evaluate the contribution of model parameters to the overall variance of R 0 . The recovery functions studied here take into account that society's capacity to provide treatment is limited when the number of infected individuals is large. Bifurcation analysis is used to establish a relationship between an alert level of prevalence and the minimum recovery time that guarantees the eradication of the disease. We also show that a backward bifurcation can occur when there are delays in the treatment of infected individuals.

Control Strategies in Multigroup Models: The Case of the Star Network Topology.

In this paper, we propose control strategies for multigroup epidemic models. We use compartmental [Formula: see text] models to study the dynamics of n host groups sharing the same source of infection in addition to the transmission among members of the same group. In particular, we consider a model for infectious diseases with free-living pathogens in the environment and a metapopulation model with a central patch. We give the detailed derivation of the target reproduction number under three public health interventions and provide the corresponding biological insights. Moreover, using the next-generation approach, we calculate the basic reproduction numbers associated with subsystems of our models and determine algebraic connections to the target reproduction number of the complete model. The analysis presented here illustrates that understanding the topological structure of the infection process and partitioning it into simple cycles is useful to design and evaluate the control strategies.

Hernia diafragmática postesofagectomía transhiatal. Una complicación excepcional / Diaphragmatic hernia after posthiatal esophagectomy. A exceptional complication

La hernia diafragmática postesofagectomía transhiatal es una complicación excepcional, esto se debe a la escasa sobrevida a largo plazo de los cánceres de esófago y a lo oligosintomático del cuadro, hecho que dificulta su diagnóstico. Existen pocas comunicaciones en la literatura de habla inglesa al respecto. No encontramos publicaciones en nuestro medio. La resección circunferencial del hiato (realizada en los tumores de 1/3 inferior esofágico) crearía una mayor predisposición para la aparición de esta complicación en los enfermos sometidos a esofagectomía transhiatal. La radiología de tórax puede ser diagnóstica, pero son la tomografía axial computada y el estudio contrastado de intestino los que confirman el diagnóstico. El tratamiento se reserva para aquellos enfermos con distress respiratorio importante y complicaciones agudas como la oclusión intestinal. La mortalidad es elevada especialmente si se presenta una complicación aguda, disminuyendo notoriamente si se realiza diagnóstico y tratamiento precoz.

Informe final: estudio cualitativo de conocimientos, actitudes y prácticas sobre malaria en los Municipios de Reyes y Guayaramerín

Contiene: Capítulo I. Ofrece una descripción de los antecedentes, la justificación y el planteamiento del problema, así como los objetivos y las variables operacionales del estudio; Capítulo II. Desarrolla la metodología, delimitando el área geográfica, la población y los sujetos de la investigación, y describe el método de la investigación cualitativa; Capítulo III. Trata sobre los resultados del estudio, recogiendo información de los participantes y dando a conocer los principales hallazgos de la investigación; Capítulo IV. Señala la discusión; Capítulo V. Presenta las conclusiones y recomendaciones sobre la base de los resultados alcanzados por el estudio.

Curso descentralizado de planificación y gerencia para el desarrollo de los distritos de salud: módulo de información general / sss

El módulo de análisis de la realidad del Distrito se basa en el estudio de las metodologías y técnicas necesarias para desarrollar la capacidad de estudiar la situación del Distrito, lo que deberá expresarse en la identificación de problemas, la selección de prioridades, la construcción de su red explicativa, así como la identificación de las causas más importantes que condicionan y determinan los problemas de salud. El propósito de desarrollar la discusión sobre el uso de dichas metodologías y técnicas, es conseguir que los participantes las interanalicen con una visión crítica, con la finalidad que comprendan su importancia y las pongan en práctica en los distritos, lo que permitirá asegurar su uso en el futuro de manera continua y sistemática

Curso descentralizado de planificación y gerencia para el desarrollo de los distritos de salud: Módulo 1 análisis de la realidad del distrito / sss

El módulo de análisis de la realidad del distrito se basa en el estudio de las metodologías y técnicas necesarias para desarrollar la capacidad de estudiar la situación del Distrito, lo que deberá expresarse en la identificación de problemas, la selección de prioridades, la construcción de su red explicativa, así como la identificación de las causas mas importantes que condicionan y determinan los problemas de salud. El propósito de desarrollar la discusión sobre el uso de dichas metodologías y técnicas, es conseguir que los participantes las interanalicen con una visión crítica, con la finalidad que comprendan su importancia y las pongan en práctica en los distritos, lo que permitirá asegurar su uso en el futuro de manera continua y sitemática

Curso descentralizado de planificación y gerencia para el desarrollo de los distritos de salud: módulo de información general / sss

El módulo de análisis de la realidad del Distrito se basa en el estudio de las metodologías y técnicas necesarias para desarrollar la capacidad de estudiar la situación del Distrito, lo que deberá expresarse en la identificación de problemas, la selección de prioridades, la construcción de su red explicativa, así como la identificación de las causas más importantes que condicionan y determinan los problemas de salud. El propósito de desarrollar la discusión sobre el uso de dichas metodologías y técnicas, es conseguir que los participantes las interanalicen con una visión crítica, con la finalidad que comprendan su importancia y las pongan en práctica en los distritos, lo que permitirá asegurar su uso en el futuro de manera continua y sistemática

Propuesta metodológica de educación permanente / sss

Se intenta lograr compartir orientaciones fundamentales que puedan servir de guía, posibilitar la estructuración y elaboración de mecanismos pertinentes que coadyuven y cualifiquen el quehacer cotidiano del trabajo