The present work shows that it is possible to analytically solve a general model to explain the transmission dynamics of SARS-CoV-2. First, the within-host model is described, and later a between-host model, where the coupling between them is the viral load of SARS-CoV-2. The within-host model describes the equations involved in the life cycle of SARS-CoV-2, and also the immune response; while that the between-Host model analyzes the dynamics of virus spread from the original source of contagion associated with bats, subsequently transmitted to a host, and then reaching the reservoir (Huanan Seafood Wholesale Market in Wuhan ), until finally infecting the human population. Show less

Obesity is associated with functional limitations in muscle performance. The true effect of obesity on skeletal muscle mass, including any interactions with aging effects, remains to be elucidated. The present study investigated the impact of obesity on the stimulation of muscle growth, based on a new model of body composition. A dataset of 44 men and 64 women was analysed. Body weight (Wt), body height (Ht), hand circumference (HdC) and waist circumference (WC) were measured. Processed by the Dahlmann-Body-Analysis (DBA) system, a new model of body composition, the increase of skeletal muscle mass (ΔSMM) compared to the individual reference weight was calculated. Muscle mass data derived by the DBA model are compared with DXA-derived predictive equations of studies representing different countries and ethnicities estimating the appendicular skeletal muscle mass. Means of these groups are tested by ANOVA. Age ranged from 18 to 72 years. All subjects had a BMI ≥ 29.7 (kg/m²). The mean values of ΔSMM as an estimate of muscle mass gain calculated by the DBA-system were 11.8 ±3.6 kg for men and 8.9 ±2.6 kg for women, respectively, demonstrating a linear, significantly rising relationship with BMI (ß > 0, p<0.001). The study population did not show a decrease in muscle mass with age in either men or women up to an age of 65 years. The results suggest that the present model has satisfactory prediction qualities to detect an increase in skeletal muscle mass associated with a growing burden of body fat. Show less

Background Typhoid fever remains a significant public health issue in Harare City, Zimbabwe, exacerbated by recurrent outbreaks between 2018 and 2020. Key challenges, including inadequate water supply and sanitation infrastructure, high population density, and limited healthcare access, have intensified the disease burden. Understanding the key transmission drivers and assessing the impact of various interventions are essential for informing policy and health strategies. Objectives This study aimed to: 1: To predict future trends in typhoid fever cases Harare City typhoid hot areas. 2: To develop a mathematical model to simulate the spread of typhoid fever incidence under different intervention scenarios and recommend evidence-based strategies for reducing the disease burden in Harare City. Methods A dynamic compartmental SIR-based model, adapted from the Pitzer Vaccine Effectiveness (VE) framework, was employed to simulate disease transmission. This model accounted for both short-cycle (human-to-human) and long-cycle (environmental) transmission pathways. Data from Harare City (2018–2020) were used for model calibration and forecasting, and sensitivity analysis was performed to assess the impact of different intervention levels. Findings The model identified inadequate sanitation, contaminated water sources, and low health- seeking behaviors as primary drivers of typhoid transmission. In the absence of interventions, the model projected a sustained high rate of transmission. However, treatment and WASH interventions could reduce the disease burden by 50–60%, while combined strategies incorporating vaccination and education led to an 80% reduction in cases. Sensitivity analysis indicated that treatment and WASH interventions were particularly impactful at moderate coverage levels. Conclusion Mathematical modeling effectively demonstrated the multifactorial drivers of typhoid fever transmission in Harare. Integrated interventions that combine WASH, vaccination, treatment, and education present the most promising approach for long-term control of the disease. The findings offer a solid, data-driven foundation for public health decision-making and resource allocation. Show less