A literature review on osteoporosis risk factors and prevention: the importance of an early approach

Osteoporosis is a condition characterized by deterioration of bone microarchitecture resulting in loss of total bone mass, decreased tissue resistance and increased susceptibility to fractures. The study in question aimed to analyze and debate the risk factors and the effectiveness of forms of prevention related to osteoporosis, given their implication for the general population and the need to disseminate safe and effective forms of behavioral management that can contribute to the decrease in the condition, mainly in the most susceptible individual. For this, 42 articles indexed in Bireme, PubMed, Scielo and UpToDate platforms were selected for discussion of the topic. Thus, it was concluded that the need for active investigation of risk factors by health professionals, as well as the encouragement of preventive practices, especially in the population with higher incidence of the disease.

Is the increased transmissibility of SARS-CoV-2 variants driven by within or outside-host processes?

Understanding the factors that increase the transmissibility of the recently emerging variants of SARS-CoV-2 can aid in mitigating the COVID-19 pandemic. The enhanced transmissibility could be attributed to enhanced within-host processes, such as contagiousness (viral shedding by an infected individual) and infectivity (the probability of a susceptible individual to get infected), or outside-host processes, such as viral stability on surfaces and in the air. We utilized a mathematical model in order to theoretically analyze the specific mechanisms of virus transfer between an infected and susceptible individual. This allowed us to examine how the within-host or outside-host processes affect the overall viral transmission. Our analysis is based the available data on the Alpha, Epsilon and Delta variants as well as the currently emerging Omicron variant. We found that the higher transmissibility of the SARS-CoV-2 variants can be attributed only to within-host processes. Specifically, enhanced contagiousness drives the Delta variant transmissibility, while the Alpha, Epsilon and Omicron are characterized by an enhanced infectivity. Since outside-host processes have little contribution to the observed increase in the transmissibility, leading stricter hygienic and behavioral measures than those that were already applied are not expected to achieve a pronounced mitigating effect.

Resources Allocation to Suppress the Spread of the Epidemic: A New Model with Consideration of Regional Influence (Preprint)

BACKGROUND During epidemics, how to allocate resources to suppress the spread of infectious disease is of great significance. Many researches focused on how to suppress the spread of infectious disease in the contact network. However, obtaining the contact network in a short period of time is difficult. OBJECTIVE When resources cannot meet the needs of multiple regions, it is necessary to consider how to allocate resources among multiple regions to limit the spread of the disease without details of the contact network. METHODS It proposed a resources allocation model to measure the cost of different allocation methods by the number of new infected individuals over a period of time. By calculating the probability of a susceptible individual being infected, it estimated the number of new infected individuals. In order to calculate the probability of a susceptible individual being infected by an infected individual in another region, conditional mutual information was introduced to estimate the strength of association relationship between regions. RESULTS Based on the proposed model, it compared the model costs of four different resources allocation methods and found three factors that affect the performance of each method, including the percentage of infected individuals, the resource coverage percentage, and the distribution of infected individuals in each region. CONCLUSIONS No method is better than other methods under any situations. When resources are allocated, the method with the least cost in a short period of time should be adopted according to the current infections, so as to control the epidemic as soon as possible.

How do I bite thee? Let me count the ways: Heterogeneity and temperature dependence in Ae. aegypti biting habits drive individual mosquito arbovirus transmission potential

In models of mosquito-borne transmission, biting rate is the most influential parameter, and understanding the role of temperature on this process is important for assessing the transmission potential of arboviruses like dengue (DENV). Further, the process of biting is assumed to be relatively homogeneous across individuals, with time-between-bites described by an exponentially distributed process. However, these assumptions have not been addressed through laboratory experimentation. We experimentally determined daily biting habits of Ae. aegypti at three temperatures (24°C, 28°C, and 32°C) and determined that there was a high degree of individual heterogeneity in biting habits (number of bites, timing of bites, etc.). There was a significantly higher proportion of females that bit at 28°C compared to both 24°C and 32°C. We further explored the consequences of biting heterogeneity using an individual-based model designed to examine whether a particular biting profile determines whether a mosquito is more or less likely to 1) become exposed given a single index case of DENV and 2) transmit to a susceptible individual. Our results indicate that biting is heterogeneous among individuals and this heterogeneity affects transmission potential of DENV. Understanding individual-level heterogeneity in biting is important and may suggest a role for high-frequency biters as significant contributors to the transmission of DENV.

Prosocial behavior of wearing a mask during an epidemic: an evolutionary explanation

In the midst of the COVID-19 pandemic, with limited or no supplies of vaccines and treatments, people and policymakers seek easy to implement and cost-effective alternatives to combat the spread of infection during the pandemic. The practice of wearing a mask, which requires change in people’s usual behavior, may reduce disease transmission by preventing the virus spread from infectious to susceptible individuals. Wearing a mask may result in a public good game structure, where an individual does not want to wear a mask but desires that others wear it. This study develops and analyzes a new intervention game model that combines the mathematical models of epidemiology with evolutionary game theory. This approach quantifies how people use mask-wearing and related protecting behaviors that directly benefit the wearer and bring some advantage to other people during an epidemic. At each time-step, a suspected susceptible individual decides whether to wear a facemask, or not, due to a social learning process that accounts for the risk of infection and mask cost. Numerical results reveal a diverse and rich social dilemma structure that is hidden behind this mask-wearing dilemma. Our results highlight the sociological dimension of mask-wearing policy.

PREMIUM CALCULATIONS FOR COMPARTMENTAL MODEL USING DISCRETE ANALOGUES OF CONTINUOUS LOSS DISTRIBUTIONS

In the present paper we consider some discrete analogues of continuous loss distributions to illustrate their actuarial applications using a simple deterministic epidemiological model. We give numerical illustrations using different parameter values of discrete analogues of continuous loss distributions. We also give level premiums for annuity assuming future premium to be paid by the susceptible individual or future claim to be made by the infected individual follow some discrete analogues of continuous loss distributions.

Kawasaki disease recurrence in the COVID-19 era: a systematic review of the literature

Kawasaki disease (KD) is a vasculitis of unknown origin of small and medium caliber blood vessels, especially involving coronary arteries and is the leading cause of acquired heart disease in childhood in developed countries. Although rarely, it can recur: most recurrences occur within 2 years of the initial episode. No data are available on incidence of recurrent KD in Europe and multiple recurrences are rarely seen. We reviewed the medical literature on Kawasaki disease recurrence and reported a new case of Kawasaki disease recurrence in a child with SARS-CoV-2 infection. We believe that in our case SARS Cov2 acted as a trigger capable to determine, in a genetically susceptible individual, a second recurrence of the disease. In the Covid-19 era we affirm the importance for Kawasaki disease to be tested for SARS Cov2 infection.

Estimating the state of the COVID-19 epidemic in France using a model with memory

In this paper, we use a deterministic epidemic model with memory to estimate the state of the COVID-19 epidemic in France, from early March until mid-December 2020. Our model is in the SEIR class, which means that when a susceptible individual (S) becomes infected, he/she is first exposed (E), i.e. not yet contagious. Then he/she becomes infectious (I) for a certain length of time, during which he/she may infect susceptible individuals around him/her, and finally becomes removed (R), that is, either immune or dead. The specificity of our model is that it assumes a very general probability distribution for the pair of exposed and infectious periods. The law of large numbers limit of such a model is a model with memory (the future evolution of the model depends not only upon its present state, but also upon its past). We present theoretical results linking the (unobserved) parameters of the model to various quantities which are more easily measured during the early stages of an epidemic. We then apply these results to estimate the state of the COVID-19 epidemic in France, using available information on the infection fatality ratio and on the distribution of the exposed and infectious periods. Using the hospital data published daily by Santé Publique France, we gather some information on the delay between infection and hospital admission, intensive care unit (ICU) admission and hospital deaths, and on the proportion of people who have been infected up to the end of 2020.

Towards Improved Social Distancing Guidelines: Space and Time Dependence of Virus Transmission from Speech-driven Aerosol Transport Between Two Individuals

It is now recognized that aerosol transport contributes to the transmission of the SARS-CoV-2 virus. Here we improve existing social distancing guidelines for airborne pathogens, which are typically given in terms of distance with vague statements (if any) about contact times. Also, estimates of inhalation of virus in a contaminated space usually assume a well-mixed environment, which is realistic for some, but not all, situations. In particular, we consider a local casual interaction of an infected individual and a susceptible individual, both maskless, account for the air flow and aerosol transport characteristics of speaking and breathing, and propose social distancing guidelines that involve both space and contact time, based on a conservative model of the interactions.