Transmission Model Research Articles

State-level disparities in cervical cancer prevention and outcomes in the U.S.: A modeling study.

Despite HPV vaccines' availability for over a decade, coverage across the US varies. While some states have tried to increase HPV vaccination coverage, most model-based analyses focus on national impacts. We evaluated hypothetical changes in HPV vaccination coverage at the national and state levels for California, New York, and Texas using a mathematical model. We developed a new mathematical model of HPV transmission and cervical cancer, creating US and state-level models, incorporating country- and state-specific vaccination coverage and cervical cancer incidence and mortality. We quantified the national and state-level impact of increasing HPV vaccination coverage to 80% by 2025 or 2030 on cervical cancer outcomes and the time to elimination defined as <4 per 100k women. Increasing vaccination coverage to 80% in Texas over ten years could reduce cervical cancer incidence by 50.9% (95% credible interval [CrI]:46.6-56.1%) by 2100, from 1.58 (CrI:1.19-2.09) to 0.78 (CrI:0.57-1.02) per 100,000 women. Similarly, New York could see a 27.3% (CrI:23.9-31.5%) reduction, from 1.43 (CrI:0.93-2.07) to 1.04 (Crl:0.66-1.53) per 100,000 women, and California a 24.4% (CrI:20.0-30.0%) reduction, from 1.01 (Crl:0.66-1.44) to 0.76 (Crl:0.50-1.09) per 100,000 women. Achieving 80% coverage in five years will provide slightly larger and sooner reductions. If the vaccination coverage levels in 2019 continue, cervical cancer elimination could occur nationally by 2051 (Crl:2034-2064), but state timelines may vary by decades. Targeting an HPV vaccination coverage of 80% by 2030 will disproportionately benefit states with low coverage and higher cervical cancer incidence. Geographically focused analyses can better inform priorities.

Stochastic Analysis for the Dual Virus Parallel Transmission Model with Immunity Delay.

In this article, the qualitative properties of a stochastic dual virus parallel transmission model with immunity delay are analyzed. First, we use Lyapunov theory to study the existence and uniqueness of the global positive solution of the proposed model. Second, the threshold values of the persistence and extinction of two viruses were obtained. Finally, the numerical simulation verifies the theoretical results. The results show that the immunity delay and the intensity of noise have important effects on the two diseases spreading in parallel.

Effectiveness and efficiency of immunisation strategies to prevent RSV among infants and older adults in Germany: a modelling study

BackgroundRecently, several novel RSV immunisation products that protect infants and older adults against RSV disease have been licensed in Europe. We estimated the effectiveness and efficiency of introducing these RSV immunisation strategies in Germany.MethodsWe used a Bayesian framework to fit a deterministic age-structured dynamic transmission model of RSV to sentinel surveillance and RSV-specific hospitalisation data in Germany from 2015 to 2019. The calibrated model was used to evaluate different RSV intervention strategies over 5 years: long-acting, single-dose monoclonal antibodies (mAbs) in high-risk infants aged 1–5 months; long-acting mAbs in all infants aged 1–5 months; seasonal vaccination of pregnant women and one-time seasonal vaccination of older adults (75 + /65 + /55 + years). We performed sensitivity analysis on vaccine uptake, seasonal vs. year-round maternal vaccination, and the effect of under-ascertainment for older adults.ResultsThe model was able to match the various RSV datasets. Replacing the current short-acting mAB for high-risk infants with long-acting mAbs prevented 1.1% of RSV-specific hospitalisations in infants per year at the same uptake. Expanding the long-acting mAB programme to all infants prevented 39.3% of infant hospitalisations per year. Maternal vaccination required a larger number to be immunised to prevent one additional hospitalisation than a long-acting mAB for the same uptake. Vaccination of adults older than 75 years at an uptake of 40% in addition to Nirsevimab in all infants prevented an additional 4.5% of all RSV hospitalisations over 5 years, with substantial uncertainty in the correction for under-ascertainment of the RSV burden.ConclusionsImmunisation has the potential to reduce the RSV disease burden in Germany.

Electromagnetic performance analysis of a novel radial compound differential field-modulated magnetic gears

Purpose The purpose of this study is to propose a new magnetic gearing device and the proposed transmission model can be applied in the field of wind power and wave energy generation gearboxes. Design/methodology/approach A novel radial differential field-modulated two-stage magnetic gear is introduced, using a unique radial differential linkage to integrate two single-stage magnetic gears. This design incorporates a magnetic isolation ring to enhance transmission efficiency by minimizing magnetic interference and preventing power circulation. The two-stage modulating ring rotor operates synchronously via a connecting bridge, ensuring system stability and efficiency. This configuration not only boosts the gear ratio but also maintains a compact structure, improving power density and efficiency. Leveraging the magnetic field modulation and differential transmission, a finite element model of this gear is developed and its electromagnetic performance is analyzed. Findings The torque density of the new radial differential field-modulated two-stage magnetic gear has increased by 44.97% compared to the traditional tandem two-stage magnetic gear. It achieves a high transmission ratio of 64 and maintains comparable power density, indicating strong torque transfer capabilities suitable for low-speed, high-torque applications. During steady-state operation, the torque pulsation difference between the two stages is minimal, ensuring stable working torque. Social implications This research not only propels the forefront of magnetic gear technology through heightened efficiency and streamlined design but also bears profound societal significance in fostering sustainable energy paradigms. By facilitating superior energy conversion efficiencies in wind turbines and wave energy converters, it plays a pivotal role in mitigating carbon emissions and accelerating the global pivot towards cleaner, renewable energy landscapes. Originality/value A magnetic gear transmission device is proposed, which can achieve high power density and large transmission ratio at the same time, and this study provides a useful reference for the design optimization of new high-performance multistage magnetic gears.

Population and transmission dynamics model to determine WHO targets for eliminating Hepatitis C virus in Thailand.

Hepatitis C Virus is endemic to many areas of Thailand, whose population structure is tending towards older age groups as birth rate and mortality decrease. With around 790,000 cases in 2019, prevalence is still relatively high, but the World Health Organisation has called for elimination of HCV by 2030. An age structured compartmental transmission model was used to explore the effectiveness of screening strategies with respect to WHO elimination goals, as well as the effect of changing population structure on the success or failure of such strategies. Population structure did not appear to affect the timeline of elimination targets and screening individuals over the age of 30 at a high (50% per year) coverage could bring forward achievement of the incidence elimination target by four years compared to baseline (approximately 6% per year). Achievement of mortality elimination targets was not reached until after the end of the simulation (2040), and intensive screening strategies did not appear to lead to incidence elimination by 2030. The model suggested that with age-targeted screening programmes incidence elimination could be brought forward by several years. However, WHO elimination goals may not be met by 2030.

Cost Apportionment Method for Transmission and Distribution Projects Based on Multiple Apportionment Factors

In today’s society, sustainability has become a key theme, and utilizing renewable energy is part of sustainability. Under the high proportion of renewable energy access, the conventional grid is gradually shifting to an active and distributed structure, which makes the existing cost apportionment method of transmission and distribution projects unable to match the actual situation. Reasonable apportionment of the costs of different voltage levels is the basis for the evaluation of transmission and distribution projects and is important for the formulation of transmission and distribution tariffs, which in turn have a significant impact on the development of renewable energy. To this end, this paper takes China’s power system as the research object and firstly analyzes the impact of the activization of the grid on the cost apportionment of transmission and distribution projects and then the inadequacy of the existing cost apportionment, which only considers a single factor and part of the cost which should be apportioned downward is still borne by this voltage level, and then combines the activation and the inherent characteristics of the power grid to extract the multiple factors to be considered for cost apportionment, and at the same time takes into account the reverse direction of the power trend, and divides the cost apportionment into two scenarios. The cost sharing model of transmission and distribution projects based on multiple apportionment factors is established. Finally, the feasibility and applicability of the model are verified by the examples of linear and reticulated grids, and the cost sharing results obtained by this method and the traditional method are compared. Using this method for the cost sharing of transmission and distribution projects, lower voltage levels will share more costs, and higher voltage levels will share fewer costs. The results show that the inclusion of the factors affecting cost sharing in the case of an active grid is more in line with the development trend of the new power system; the cost apportionment method based on multiple sharing factors makes the results fairer; and the inclusion of the power trend conduction relationship in the sharing process reflects the essential attributes of the grid. This is conducive to improving the operational efficiency of the power grid and promoting the long-term sustainability of the power system.

Cost-effectiveness of nonavalent vs bivalent HPV vaccine in Polish setting.

Human papillomavirus (HPV) is a prevalent sexually transmitted infection with significant implications for public health. In Poland, a nationwide vaccination program offers a choice between the 9-valent (9v) and 2-valent (2v) HPV vaccines. We aimed to assess the cost-effectiveness of the 9v vs 2v vaccine from the public payer perspective in Poland. A cost-effectiveness analysis was conducted to compare the public health and economic benefits of using 9v vs 2v vaccine in Poland over 100-year horizon using a previously published deterministic dynamic transmission model. A target population of girls and boys aged 12-13 years was considered. The model was populated with local epidemiological inputs, utilities, and costs, including vaccine and administration costs, as well as costs related to medical procedures for HPV-related diseases. The 9v vaccine reduced the prevalence of HPV infections and HPV-related diseases substantially more than 2v vaccine when both are compared to no vaccination strategy. The total discounted cost savings of using the 9v vaccine instead of 2v, excluding the vaccine costs, amounted to EUR 66 million. The incremental cost-effectiveness ratio amounted to 8094 EUR per quality-adjusted life year, much below the official cost-effectiveness threshold in Poland set up at the three times the annual gross domestic product per capita. 9v cost-effectiveness ratio remained unchanged when shorter time-horizons of 20, 40, 60, or 80 years were considered. Using 9v HPV vaccine in Poland is highly cost-effective compared to the 2v vaccine.

Machine learning for locally periodic structure transmission modelling

This research aims to obtain an analytical transmission model for locally periodic structures with the approach of data-driven physics. So far, this task has been done mainly numerically for non-trivial geometries. From a dataset of Bloch phases generated for given frequency band and structure geometry parameters, it is possible to learn equations relating dispersion relation to axis-symmetric geometry. The dataset is transformed into a lower-dimensional space by applying Principal Component Analysis (PCA) to reduce the complexity of the problem. In the newly obtained coordinate system, the lower-dimensional patterns are extracted via symbolic regression. The resulting model is interpretable in terms of underlying physics and can be used, e.g., to propose an optimized design for a desired band gap width. Note that this has been so far possible only with numerical optimization repeatedly going back and forth from geometry to the dispersion relation, and hence, it significantly contributes to the overall readability of the system features.

Measured and predicted sound transmission through a laboratory concrete floor

The direct sound transmission through a simple, massive, homogeneous building element with and without lining is investigated experimentally and compared with analytical and empirical models from the literature. A 150 mm thick concrete floor and a 100 mm thick floating floor were measured in the floor transmission facility of the National Research Council Canada, i.e. without flanking sound transmission. In addition to the sound reduction index and the normalized impact sound pressure level, loss factors, radiation efficiencies, and mean squared velocities were recorded in the laboratory. The measured data is compared to established models of sound transmission. A focus is placed on the calculation model of ISO 12354-1 (Appendix B), which uses calculated radiation efficiencies and loss factors to predict the sound reduction index of heavy, homogeneous building elements. Some difficulties with the calculation model and the examples in the standard are discussed. In principle, the results in this study show that the calculation model of ISO 12354-1 gives good estimates when the correct input parameters are used. However, deviations between the calculated and the measured loss factors and radiation efficiencies have large effects on the accuracy of the estimates, particularly in the region around the coincidence frequency.

Stability Analysis of the Transmission Model of TB-HIV Co-Dynamics with Vaccination and Treatment

This study aims to analyse and determine the stability of the equilibrium point of the spread model consists of TB infection, HIV infection, and TB-HIV co-infection disease. This model considers eight compartments, namely unvaccinated susceptible, vaccinated susceptible, exposed, infected with TB, infected with HIV, infected with TB and HIV, treatment, and recovered by considering vaccination and treatment in the compartments as the strategies to manage spread of the diseases. The stability of non-endemic equilibrium point is carried out by determining the basic reproduction number and eigenvalues. Simulation is conducted to investigate effect of vaccination and treatment. By giving appropriate values of parameters and varying values of vaccination rate we found that increasing value of vaccination rate will reduce and eliminate TB infection, HIV infection, and TB-HIV co-infection disease from the population. The curve solutions of the dynamics of each compartment are given to confirm the analytical results.

Trade risk transmission of global cobalt industrial chain based on multi-layer network

In order to study the potential systemic risk transmission in cobalt trade, this paper combined the infectious disease model with complex networks to build a multi-layer network trade risk transmission model for cobalt trade based on the transmission of export restrictions and bilateral friction in a single country, in order to simulate the degree of impact of risk transmission in cobalt industry chain, identify key countries and risk transmission paths. The results show that multi-layer network risk transmission of global cobalt trade based on two communication forms has the characteristics of “robust and fragile”. In addition, the risk transmission situation based on bilateral frictions is mainly transmitted by core countries and direct contacts. The risk transmission based on the export restriction of a single country is mainly through direct contact, indirect contact and regional transmission. We also find that the multi-layer trade network of global cobalt trade can resist the bilateral frictional transmission mode better than the transmission mode of single country export restriction. The results can support policy makers to optimize the cobalt trade structure and mitigate the negative impact of trade disruptions.

Pairwise Accelerated Failure Time Regression Models for Infectious Disease Transmission in Close-Contact Groups With External Sources of Infection.

Many important questions in infectious disease epidemiology involve associations between covariates (e.g., age or vaccination status) and infectiousness or susceptibility. Because disease transmission produces dependent outcomes, these questions are difficult or impossible to address using standard regression models from biostatistics. Pairwise survival analysis handles dependent outcomes by calculating likelihoods in terms of contact interval distributions in ordered pairs of individuals. The contact interval in the ordered pair is the time from the onset of infectiousness in to infectious contact from to , where an infectious contact is sufficient to infect if they are susceptible. Here, we introduce a pairwise accelerated failure time regression model for infectious disease transmission that allows the rate parameter of the contact interval distribution to depend on individual-level infectiousness covariates for , individual-level susceptibility covariates for , and pair-level covariates (e.g., type of relationship). This model can simultaneously handle internal infections (caused by transmission between individuals under observation) and external infections (caused by environmental or community sources of infection). We show that this model produces consistent and asymptotically normal parameter estimates. In a simulation study, we evaluate bias and confidence interval coverage probabilities, explore the role of epidemiologic study design, and investigate the effects of model misspecification. We use this regression model to analyze household data from Los Angeles County during the 2009 influenza A (H1N1) pandemic, where we find that the ability to account for external sources of infection increases the statistical power to estimate the effect of antiviral prophylaxis.

Single and multi-threaded power flow algorithm for integrated transmission-distribution-residential networks

The rapid development of renewable sources has significantly increased interdependencies between electricity networks of all voltage levels, leading to bidirectional flows between transmission and distribution networks, and requiring analysis of Integrated Transmission-Distribution (ITD) network. The interconnectivity is further amplified by additional coupling with electricity, gas, heat and hydrogen networks, on both national and regional levels. Moreover, installation of solar, wind and storage on customers’ premises has indicated that residential networks need to be included in the overall integrated model, called Integrated Transmission-Distribution-Residential (ITDR) network. The main goal of the paper is to develop a general model of the ITD/ITDR networks and to solve the power-flow problem on large-scale networks in an efficient way. The general model includes three-phase transmission and multi-phase distribution models, as well as accurate control strategies for traditional and electronically coupled electricity resources. The proposed model is solved via novel single-threaded power flow procedure, which incorporates new network elements’ models and the developed algorithm for integrated power flow calculations in different domains. This is further improved by developing a multi-threaded approach. Analyses on a small-scale ITD network have shown that single- and multi-threaded approaches are, respectively, (1.5–4) and (2–5) times faster compared to the state-of-the-art procedures. As network size increases, the efficiency of the proposed multi-threaded procedure becomes more pronounced compared to the single-threaded one (up to 2.39 times).

A new model of the impact of information dissemination with emotional responses on disease transmission in multilayer networks

During disease transmission, the dissemination of information about the disease prompts safety concerns among individuals. Individuals’ various emotional responses to information may affect infection prevention measures and, consequently, disease transmission. In this paper, we propose a new coupled information and disease transmission model with emotional factors in multiplex networks. Our specific focus is on the impact of diverse emotional responses on the dynamics process. We employ the Microscopic Markov Chain Approach (MMCA) to analyze the model, and obtaining state transfer equations, and deriving the disease transmission threshold. Extensive numerical simulations show that dissemination of information by relevant authorities motivates individuals to adopt scientific self-protective behaviors, thus helping to control disease transmission. Furthermore, individuals who have different emotional responses after obtaining information have varying effects on disease transmission, and reducing the anxiety response or increasing the calm response of individuals can more effectively decrease the scale of disease transmission and increase the disease transmission threshold. In summary, improving the quality of information released by the emergency management department, reducing the individual’s anxiety response, and encouraging the adoption of positive and effective protective measures are of paramount importance for epidemic prevention and control.

Horizontal gradient effects on the flow stability in a cylindrical container in a Bèrnard–Marangoni problem

This study assesses the flow stability of the Bénard–Marangoni (BM) problem, a thermoconvective scenario occurring in an annular domain. The system is heated from below, with a linearly decreasing horizontal temperature profile from the inner to the outer wall. The top surface of the domain is open to the atmosphere, while the lateral walls are adiabatic. The analysis focuses on the effects of the Bond number, which represents capillarity or buoyancy effects, and the horizontal temperature gradient on the flow stability for three different Prandtl numbers, indicative of viscosity effects in fluids ranging from typical gases to n-butanol. Three different models for heat transmission to the atmosphere are also considered using the Biot number. The results indicate that, for the two largest Prandtl numbers (50 and 5), multiple competing solutions emerge in localized regions of the Bond–temperature gradient plane. The boundaries between these regions include co-dimension two points, where two solutions coexist, and at least one co-dimension three point for each Prandtl and Biot number combination. These transitions show a strong dependency on both the Bond and Prandtl numbers. Additionally, as anticipated, the solution space is more complex for the smallest Prandtl number (Pr=1), with seven competing solutions identified in the plane.

Influenza vaccine allocation in tropical settings under constrained resources.

Influenza virus seasonality, synchronicity, and vaccine supply differ substantially between temperate and tropical settings, and optimal vaccination strategy may differ on this basis. Many national vaccine recommendations focus on high-risk groups, elderly populations, and healthcare workers despite previous analyses demonstrating broad benefits to vaccinating younger high-contact age groups. In this study, we parameterized an age-structured nonseasonal asynchronous epidemiological model of influenza virus transmission for a tropical low-income setting. We evaluated timing and age allocation of vaccines across vaccine supplies ranging from 10 to 90% using decade-based age groups. Year-round vaccination was beneficial when compared with more concentrated annual vaccine distribution. When targeting a single age group for vaccine prioritization, maximum vaccine allocation to the 10-19 high-contact age group minimized annual influenza mortality for all but one vaccine supply. When evaluating across all possible age allocations, optimal strategies always allocated a plurality of vaccines to school-age children (10-19). The converse, however, was not true as not all strategies allocating a plurality to children aged 10-19 minimized mortality. Allocating a high proportion of vaccine supply to the 10-19 age group is necessary but not sufficient to minimize annual mortality as distribution of remaining vaccine doses to other age groups also needs to be optimized. Strategies focusing on indirect benefits (vaccinating children) showed higher variance in mortality outcomes than strategies focusing on direct benefits (vaccinating the elderly). However, the indirect benefit approaches showed a lower mean mortality and a lower minimum mortality than vaccination focused on the elderly.

Reconciling founder variant multiplicity of HIV-1 infection with the rate of CD4+ decline.

HIV-1 transmission precipitates a stringent genetic bottleneck, with 75% of new infections initiated by a single genetic variant. Where multiple variants initiate infection, recipient set point viral load (SpVL) and the rate of CD4+ T cell decline may be elevated, but these findings remain inconsistent. Here, we summarised the evidence for this phenomenon, then tested whether previous studies possessed sufficient statistical power to reliably identify a true effect of multiple variant infection leading to higher SpVL. Next, we combined models of HIV-1 transmission, heritability and disease progression to understand whether available data suggest a faster CD4+ T cell decline would be expected to associated with multiple variant infection, without an explicit dependency between the two. First, we found that most studies had insufficient power to identify a true significant difference, prompting an explanation for previous inconsistencies. Next, our model framework revealed we would not expect to observe a positive association between multiple variant infections and faster CD4+ T cell decline, in the absence of an explicit dependency. Consequently, while empirical evidence may be consistent with a positive association between multiple variant infection and faster CD4+ T cell decline, further investigation is required to establish a causal basis.

Spatial distribution of poultry farms using point pattern modelling: A method to address livestock environmental impacts and disease transmission risks.

The distribution of farm locations and sizes is paramount to characterize patterns of disease spread. With some regions undergoing rapid intensification of livestock production, resulting in increased clustering of farms in peri-urban areas, measuring changes in the spatial distribution of farms is crucial to design effective interventions. However, those data are not available in many countries, their generation being resource-intensive. Here, we develop a farm distribution model (FDM), which allows the prediction of locations and sizes of poultry farms in countries with scarce data. The model combines (i) a Log-Gaussian Cox process model to simulate the farm distribution as a spatial Poisson point process, and (ii) a random forest model to simulate farm sizes (i.e. the number of animals per farm). Spatial predictors were used to calibrate the FDM on intensive broiler and layer farm distributions in Bangladesh, Gujarat (Indian state) and Thailand. The FDM yielded realistic farm distributions in terms of spatial clustering, farm locations and sizes, while providing insights on the factors influencing these distributions. Finally, we illustrate the relevance of modelling realistic farm distributions in the context of epidemic spread by simulating pathogen transmission on an array of spatial distributions of farms. We found that farm distributions generated from the FDM yielded spreading patterns consistent with simulations using observed data, while random point patterns underestimated the probability of large outbreaks. Indeed, spatial clustering increases vulnerability to epidemics, highlighting the need to account for it in epidemiological modelling studies. As the FDM maintains a realistic distribution of farm location and sizes, its use to inform mathematical models of disease transmission is particularly relevant for regions where these data are not available.

Choice of landscape discretisation method affects the inferred rate of spread in wildlife disease spread models

Disease modelling at the livestock-wildlife interface is an important topic for which discrete-space models are used for the wildlife component. One prominent example is African Swine Fever, where wild boar play an influential role as reservoirs of disease spillover into domestic pig farms. In this paper, we present a simulation study that demonstrates the impact of seemingly arbitrary choices of landscape discretisation method on the inferred rate of spread within the model. We use an ordinary differential equation model to implement a simplified model of disease transmission between discrete groups of wild boar with spillover into domestic pig farms contained within a homogeneous landscape. We examine a range of scenarios whereby the landscape is discretised into wild boar patches of varying size and shape, and compare the rate of spread between domestic pig farms placed at fixed points on the landscape. Our results demonstrate a non-monotonic relationship between patch size and rate of spread, which is particularly unstable and unpredictable for square and triangular shaped patches. Discretisation of the landscape into hexagons appears to produce a more stable relationship between patch size and rate of spread for the three types of transmission kernel we investigated. Although the rate of disease spread does converge to a stable value, this occurs at patch sizes that are much smaller than would be used in practice for wild boar. We conclude that outputs of disease models containing a wildlife component should not be considered to be robust to arbitrary choices for patch size and placement, but rather as a source of uncertainty to be examined using sensitivity analysis. Furthermore, we strongly recommend the use of hexagons rather than squares or right triangles for landscape discretisation.

A deterministic Analysis of an Age-Gender structured model for malaria transmission dynamics

Objectives: Children below five years and women especially pregnant women are at high risk of malaria infection and death due to their weak immunity and exposition to mosquitoes. Different studies have been undertaken considering only the age structured model and other factors but did not take into account the gender. The objective of this work is to develop and analyze the malaria transmission model including this structure, to contribute on the existing measures and mechanisms to eradicate malaria in Rwanda.Methods: The dynamic malaria transmission model considering age and gender structure was developed and analyzed. To study the dynamics of disease, the basic reproduction number was analytically computed and numerically estimated and the normalized forward sensitivity index was used to highlight its sensitive parameters.Results: The most positive sensitive parameters in the model are the force of infection and infection rate for vectors and Infection rate for female of 5 years and above. The most negative sensitive parameters are the per capita death rate for vectors and humans.Conclusion: To control the spread of malaria in Rwanda, the biting and infection rate should be decreased.Therefore, women must comply with government measures against malaria and educate children about it.