Pub Date : 2025-08-08DOI: 10.1016/j.epidem.2025.100851
Jana S. Huisman , Shotaro Torii , Htet Kyi Wynn , Charles Gan , Irene K. Voellmy , Michael Huber , Timothy R. Julian , Tamar Kohn
Noroviruses and enteroviruses are major causes of endemic gastrointestinal disease associated with substantial disease burden. However, viral gastroenteritis is often diagnosed based on symptoms, with etiology infrequently tested or reported, so little information exists on community-level transmission dynamics. In this study, we demonstrate that norovirus (NoV) genogroup II and enterovirus (EV) viral loads in wastewater reveal transmission dynamics of these viruses. We report NoV and EV concentrations in wastewater from 363 samples between December 5 2020 and October 10 2022 (sampled every second day). Virus concentrations in wastewater were low during 2021, and increased in 2022. Wastewater recapitulated periods of increased clinical cases, and also identified silent waves of transmission. We used the measured wastewater loads to estimate the effective reproductive number (Re). The Re for both NoV and EV peaked between 1.1 and 1.2. However, the usual seasonality of NoV transmission was upended by non-pharmaceutical interventions implemented to mitigate the COVID-19 pandemic, leading to correlated transmission dynamics of NoV GII and EV during 2021–2022. This highlights the use of wastewater to understand transmission dynamics of endemic enteric viruses and estimate relevant epidemiological parameters, including Re.
{"title":"Transmission dynamics of Norovirus GII and Enterovirus in Switzerland during the COVID-19 pandemic (2021–2022) as evidenced in wastewater","authors":"Jana S. Huisman , Shotaro Torii , Htet Kyi Wynn , Charles Gan , Irene K. Voellmy , Michael Huber , Timothy R. Julian , Tamar Kohn","doi":"10.1016/j.epidem.2025.100851","DOIUrl":"10.1016/j.epidem.2025.100851","url":null,"abstract":"<div><div>Noroviruses and enteroviruses are major causes of endemic gastrointestinal disease associated with substantial disease burden. However, viral gastroenteritis is often diagnosed based on symptoms, with etiology infrequently tested or reported, so little information exists on community-level transmission dynamics. In this study, we demonstrate that norovirus (NoV) genogroup II and enterovirus (EV) viral loads in wastewater reveal transmission dynamics of these viruses. We report NoV and EV concentrations in wastewater from 363 samples between December 5 2020 and October 10 2022 (sampled every second day). Virus concentrations in wastewater were low during 2021, and increased in 2022. Wastewater recapitulated periods of increased clinical cases, and also identified silent waves of transmission. We used the measured wastewater loads to estimate the effective reproductive number (R<sub>e</sub>). The R<sub>e</sub> for both NoV and EV peaked between 1.1 and 1.2. However, the usual seasonality of NoV transmission was upended by non-pharmaceutical interventions implemented to mitigate the COVID-19 pandemic, leading to correlated transmission dynamics of NoV GII and EV during 2021–2022. This highlights the use of wastewater to understand transmission dynamics of endemic enteric viruses and estimate relevant epidemiological parameters, including R<sub>e</sub>.</div></div>","PeriodicalId":49206,"journal":{"name":"Epidemics","volume":"52 ","pages":"Article 100851"},"PeriodicalIF":2.4,"publicationDate":"2025-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144879110","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-07DOI: 10.1016/j.epidem.2025.100850
Jiani Chen , Deven V. Gokhale , Ludy Registre Carmola , Liang Liu , Pejman Rohani , Justin Bahl
RSV and seasonal influenza are two of the most prevalent causes of respiratory infection in the U.S. In this study, we used weekly positive case reports and genetic surveillance data to characterize the circulation of these viruses in the United States between 2011 and 2019 and a mathematical modeling approach to explore their potential interaction at a regional level. Our analyses showed that RSV and seasonal influenza co-circulate with different relative epidemic sizes and seasonal overlaps across regions and seasons. We found that RSV had a different evolutionary dynamic compared to seasonal influenza and that local persistence may play a role in underlying annual epidemics. Our analysis supports a potential competitive interaction between RSV and seasonal influenza in most regions across the United States. The multiple-pathogen modeling framework suggests that cross-immunity following infection of either virus might be one of the key drivers of viral competition. However, this finding is based on model-derived inferences and limited surveillance data; further investigation is needed to confirm its robustness and gain a better understanding of the underlying mechanisms. These findings underscore the importance of continued research into the immunological and ecological mechanisms of viral inference, which might be important for the development of more effective protective strategies against co-circulating respiratory viruses.
{"title":"Characterizing potential interaction between respiratory syncytial virus and seasonal influenza in the U.S.","authors":"Jiani Chen , Deven V. Gokhale , Ludy Registre Carmola , Liang Liu , Pejman Rohani , Justin Bahl","doi":"10.1016/j.epidem.2025.100850","DOIUrl":"10.1016/j.epidem.2025.100850","url":null,"abstract":"<div><div>RSV and seasonal influenza are two of the most prevalent causes of respiratory infection in the U.S. In this study, we used weekly positive case reports and genetic surveillance data to characterize the circulation of these viruses in the United States between 2011 and 2019 and a mathematical modeling approach to explore their potential interaction at a regional level. Our analyses showed that RSV and seasonal influenza co-circulate with different relative epidemic sizes and seasonal overlaps across regions and seasons. We found that RSV had a different evolutionary dynamic compared to seasonal influenza and that local persistence may play a role in underlying annual epidemics. Our analysis supports a potential competitive interaction between RSV and seasonal influenza in most regions across the United States. The multiple-pathogen modeling framework suggests that cross-immunity following infection of either virus might be one of the key drivers of viral competition. However, this finding is based on model-derived inferences and limited surveillance data; further investigation is needed to confirm its robustness and gain a better understanding of the underlying mechanisms. These findings underscore the importance of continued research into the immunological and ecological mechanisms of viral inference, which might be important for the development of more effective protective strategies against co-circulating respiratory viruses.</div></div>","PeriodicalId":49206,"journal":{"name":"Epidemics","volume":"52 ","pages":"Article 100850"},"PeriodicalIF":2.4,"publicationDate":"2025-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144831576","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-06DOI: 10.1016/j.epidem.2025.100848
Pleuni S. Pennings
Drug resistance is a problem in many pathogens. While overall, levels of resistance have risen in recent decades, there are many examples where after an initial rise, levels of resistance have stabilized. The stable coexistence of resistance and susceptibility has proven hard to explain – in most evolutionary models, either resistance or susceptibility ultimately “wins” and takes over the population. Here, we show that a simple model, mathematically akin to mutation-selection balance theory, can explain several key observations about drug resistance: (1) the stable coexistence of resistant and susceptible strains (2) at levels that depend on population-level drug usage and (3) with resistance often due to many different strains (resistance is present on many different genetic backgrounds). The model is applicable to resistance due to both mutations and horizontal gene transfer (HGT). It predicts that new resistant strains should continuously appear (through mutation or HGT and positive selection within treated hosts) and disappear (due to a fitness cost of resistance). The result is that while resistance is stable, which strains carry resistance is constantly changing. We used data from a longitudinal genomic study on E. coli in Norway to test this prediction for resistance to five different drugs and found that, consistent with the model, most resistant strains indeed disappear quickly after they appear in the dataset. Having a model that explains the dynamics of drug resistance will allow us to plan science-backed interventions to reduce the burden of drug resistance.
{"title":"Explaining the stable coexistence of drug-resistant and -susceptible pathogens: the resistance acquisition purifying selection model","authors":"Pleuni S. Pennings","doi":"10.1016/j.epidem.2025.100848","DOIUrl":"10.1016/j.epidem.2025.100848","url":null,"abstract":"<div><div>Drug resistance is a problem in many pathogens. While overall, levels of resistance have risen in recent decades, there are many examples where after an initial rise, levels of resistance have stabilized. The stable coexistence of resistance and susceptibility has proven hard to explain – in most evolutionary models, either resistance or susceptibility ultimately “wins” and takes over the population. Here, we show that a simple model, mathematically akin to mutation-selection balance theory, can explain several key observations about drug resistance: (1) the stable coexistence of resistant and susceptible strains (2) at levels that depend on population-level drug usage and (3) with resistance often due to many different strains (resistance is present on many different genetic backgrounds). The model is applicable to resistance due to both mutations and horizontal gene transfer (HGT). It predicts that new resistant strains should continuously appear (through mutation or HGT and positive selection within treated hosts) and disappear (due to a fitness cost of resistance). The result is that while resistance is stable, <em>which</em> strains carry resistance is constantly changing. We used data from a longitudinal genomic study on <em>E. coli</em> in Norway to test this prediction for resistance to five different drugs and found that, consistent with the model, most resistant strains indeed disappear quickly after they appear in the dataset. Having a model that explains the dynamics of drug resistance will allow us to plan science-backed interventions to reduce the burden of drug resistance.</div></div>","PeriodicalId":49206,"journal":{"name":"Epidemics","volume":"52 ","pages":"Article 100848"},"PeriodicalIF":2.4,"publicationDate":"2025-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144907266","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-07-22DOI: 10.1016/j.epidem.2025.100843
Jingsi Xu , Martín López-García , Thomas House , Ian Hall
Interpreting the viral mechanism of SARS-CoV-2 based on the human body level is critical for developing more efficient interventions. Due to the limitation of data, limited models consider the viral dynamics of the early phase of infection. The Human Challenge Study (Killingley et al., 2022) enables us to obtain data from inoculation to the 14th day after infection, which provides an overview of the dynamics of SARS-CoV-2 infection within the host. In the Human Challenge Study, each volunteer was inoculated with 10TCID50, approximately 55PFU, of a wild-type of virus (Killingley et al., 2022), and the data indicates that the viral load reduced below the detectable level within a day.
The simplified within-host models developed by Xu et al. (2023) explain the data from the Human Challenge Study (Killingley et al., 2022). However, they do not explain the viral decay from Day 0 to Day 1. Hence, in this paper, we aim to develop a new viral mechanism to explain this phenomenon. Based on the simplified within-host models developed by Xu et al. (2023), we consider that the virus will first go through an adjustment phase and then start to replicate. A new dose-response model is developed to evaluate the probability of infection by constructing a boundary problem. We will discuss this viral mechanism and fit the model to the data of the Human Challenge Study (Killingley et al., 2022) by adopting AMC-SMC (approximate Bayesian computation-sequential Monte Carlo). Based on the results of parameter inference, we estimate that the adjusted viral load is around 1% of the inoculated viral load.
基于人体水平解释SARS-CoV-2的病毒机制对于制定更有效的干预措施至关重要。由于数据的限制，有限的模型考虑了感染早期的病毒动力学。人类挑战研究（Killingley et al., 2022）使我们能够获得从接种到感染后第14天的数据，从而概述了宿主内SARS-CoV-2感染的动态。在人类挑战研究中，每位志愿者接种了10TCID50，约55PFU的野生型病毒（Killingley et al., 2022），数据表明病毒载量在一天内降至可检测水平以下。Xu等人（2023）开发的简化宿主内模型解释了人类挑战研究（Killingley等人，2022）的数据。然而，它们并不能解释病毒从第0天到第1天的衰减。因此，在本文中，我们的目标是建立一个新的病毒机制来解释这一现象。根据Xu等人（2023）开发的简化宿主内模型，我们认为病毒将首先经历一个调整阶段，然后开始复制。建立了一种新的剂量-反应模型，通过构造边界问题来评估感染的概率。我们将讨论这种病毒机制，并通过采用AMC-SMC（近似贝叶斯计算-顺序蒙特卡罗）将模型拟合到人类挑战研究（Killingley等人，2022）的数据中。根据参数推断的结果，我们估计调整后的病毒载量约为接种病毒载量的1%。
{"title":"Modelling the dynamics of SARS-CoV-2 during the first 14 days of infection","authors":"Jingsi Xu , Martín López-García , Thomas House , Ian Hall","doi":"10.1016/j.epidem.2025.100843","DOIUrl":"10.1016/j.epidem.2025.100843","url":null,"abstract":"<div><div>Interpreting the viral mechanism of SARS-CoV-2 based on the human body level is critical for developing more efficient interventions. Due to the limitation of data, limited models consider the viral dynamics of the early phase of infection. The Human Challenge Study (Killingley et al., 2022) enables us to obtain data from inoculation to the 14th day after infection, which provides an overview of the dynamics of SARS-CoV-2 infection within the host. In the Human Challenge Study, each volunteer was inoculated with 10TCID50, approximately 55PFU, of a wild-type of virus (Killingley et al., 2022), and the data indicates that the viral load reduced below the detectable level within a day.</div><div>The simplified within-host models developed by Xu et al. (2023) explain the data from the Human Challenge Study (Killingley et al., 2022). However, they do not explain the viral decay from Day 0 to Day 1. Hence, in this paper, we aim to develop a new viral mechanism to explain this phenomenon. Based on the simplified within-host models developed by Xu et al. (2023), we consider that the virus will first go through an adjustment phase and then start to replicate. A new dose-response model is developed to evaluate the probability of infection by constructing a boundary problem. We will discuss this viral mechanism and fit the model to the data of the Human Challenge Study (Killingley et al., 2022) by adopting AMC-SMC (approximate Bayesian computation-sequential Monte Carlo). Based on the results of parameter inference, we estimate that the adjusted viral load is around 1% of the inoculated viral load.</div></div>","PeriodicalId":49206,"journal":{"name":"Epidemics","volume":"52 ","pages":"Article 100843"},"PeriodicalIF":2.4,"publicationDate":"2025-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144781205","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-07-18DOI: 10.1016/j.epidem.2025.100842
Katia Koelle , Brooke Lappe , Benjamin A. Lopman , Max S.Y. Lau , Emma Viscidi , Katherine B. Carlson
Norovirus diversity has major implications for vaccine design. The number of circulating genogroups and genotypes, and the way this viral diversity interacts at the population level, will factor into how many and which genotypes should be included in an effective vaccine. Here, we develop an age-stratified, multi-strain model for norovirus to project potential population-level impacts of different vaccine formulations on genotype-specific and overall annual attack rates. Our model assumes that vaccination impacts susceptibility to infection but not infectiousness or the risk of developing disease. We parameterize the baseline model (without vaccination) based on literature estimates and the ability to recover observed epidemiological patterns. We then simulate this model under seven different potential vaccine formulations, initially assuming only pediatric vaccination. While we find that increases in coverage result in declines in annual norovirus attack rates for all formulations considered, we also find that vaccine formulations that include genotype GII.4 would be most effective at lowering overall norovirus attack rates. Inclusion of additional genotypes in a vaccine would further lower attack rates but more incrementally, with the addition of GI.3, GII.2, GII.3, and GII.6 together having a similar impact to that of GII.4 alone on reducing overall norovirus incidence. We further find that transient dynamics are expected for 10-20 years following roll-out with any pediatric vaccine. During this time, there may be unanticipated changes in genotype circulation patterns, although long-term increases in non-vaccine genotype attack rates above baseline levels are not expected. Finally, we anticipate that annual vaccination of older-aged individuals with a GII.4-containing vaccine can, under certain conditions but not others, provide appreciable direct benefits to individuals in this age group beyond what pediatric vaccination affords. Together, our results indicate that there is a clear population-level benefit of primary pediatric vaccination with a GII.4-inclusive norovirus vaccine plus incremental value of other genotypes, with additional direct benefits of annual vaccination to older adults provided that vaccination results in a considerable (multi-month) duration of broadly protective immunity to infection. More empirical studies are needed to validate the structure of the model and refine its parameterization, both of which affect projections of vaccine impact.
{"title":"Projecting the population-level impact of norovirus vaccines","authors":"Katia Koelle , Brooke Lappe , Benjamin A. Lopman , Max S.Y. Lau , Emma Viscidi , Katherine B. Carlson","doi":"10.1016/j.epidem.2025.100842","DOIUrl":"10.1016/j.epidem.2025.100842","url":null,"abstract":"<div><div>Norovirus diversity has major implications for vaccine design. The number of circulating genogroups and genotypes, and the way this viral diversity interacts at the population level, will factor into how many and which genotypes should be included in an effective vaccine. Here, we develop an age-stratified, multi-strain model for norovirus to project potential population-level impacts of different vaccine formulations on genotype-specific and overall annual attack rates. Our model assumes that vaccination impacts susceptibility to infection but not infectiousness or the risk of developing disease. We parameterize the baseline model (without vaccination) based on literature estimates and the ability to recover observed epidemiological patterns. We then simulate this model under seven different potential vaccine formulations, initially assuming only pediatric vaccination. While we find that increases in coverage result in declines in annual norovirus attack rates for all formulations considered, we also find that vaccine formulations that include genotype GII.4 would be most effective at lowering overall norovirus attack rates. Inclusion of additional genotypes in a vaccine would further lower attack rates but more incrementally, with the addition of GI.3, GII.2, GII.3, and GII.6 together having a similar impact to that of GII.4 alone on reducing overall norovirus incidence. We further find that transient dynamics are expected for 10-20 years following roll-out with any pediatric vaccine. During this time, there may be unanticipated changes in genotype circulation patterns, although long-term increases in non-vaccine genotype attack rates above baseline levels are not expected. Finally, we anticipate that annual vaccination of older-aged individuals with a GII.4-containing vaccine can, under certain conditions but not others, provide appreciable direct benefits to individuals in this age group beyond what pediatric vaccination affords. Together, our results indicate that there is a clear population-level benefit of primary pediatric vaccination with a GII.4-inclusive norovirus vaccine plus incremental value of other genotypes, with additional direct benefits of annual vaccination to older adults provided that vaccination results in a considerable (multi-month) duration of broadly protective immunity to infection. More empirical studies are needed to validate the structure of the model and refine its parameterization, both of which affect projections of vaccine impact.</div></div>","PeriodicalId":49206,"journal":{"name":"Epidemics","volume":"52 ","pages":"Article 100842"},"PeriodicalIF":3.0,"publicationDate":"2025-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144672569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-07-16DOI: 10.1016/j.epidem.2025.100846
Fabrícia F. Nascimento , Sanjay R. Mehta , Susan J. Little , Erik M. Volz
The robustness and statistical efficiency of phylodynamic models have been tested by many investigators. However, little attention has been given to model specification and inductive bias that can occur if the model is misspecified or provides an overly simplistic representation of the evolutionary process. Here, we carried out a study involving the simulation of HIV epidemics using a complex model and calibrated to men who have sex with men from San Diego, USA. We then used this epidemic trajectory to simulate genealogies, sequence alignments equivalent to HIV partial pol gene and the complete genome. We proceeded to estimate migration rates using a simplistic representation of the epidemiological model by testing model-based phylodynamics and phylogeographic methods. We observed that even though there were some biases on the estimates using a simplistic representation of the epidemiological model, we were still able to estimate the migration rates depending on the method and sample size used in the analyses.
{"title":"Robust phylodynamic inference and model specification for HIV transmission dynamics","authors":"Fabrícia F. Nascimento , Sanjay R. Mehta , Susan J. Little , Erik M. Volz","doi":"10.1016/j.epidem.2025.100846","DOIUrl":"10.1016/j.epidem.2025.100846","url":null,"abstract":"<div><div>The robustness and statistical efficiency of phylodynamic models have been tested by many investigators. However, little attention has been given to model specification and inductive bias that can occur if the model is misspecified or provides an overly simplistic representation of the evolutionary process. Here, we carried out a study involving the simulation of HIV epidemics using a complex model and calibrated to men who have sex with men from San Diego, USA. We then used this epidemic trajectory to simulate genealogies, sequence alignments equivalent to HIV partial <em>pol</em> gene and the complete genome. We proceeded to estimate migration rates using a simplistic representation of the epidemiological model by testing model-based phylodynamics and phylogeographic methods. We observed that even though there were some biases on the estimates using a simplistic representation of the epidemiological model, we were still able to estimate the migration rates depending on the method and sample size used in the analyses.</div></div>","PeriodicalId":49206,"journal":{"name":"Epidemics","volume":"52 ","pages":"Article 100846"},"PeriodicalIF":3.0,"publicationDate":"2025-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144655353","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-07-16DOI: 10.1016/j.epidem.2025.100845
David O’Gara , Cliff C. Kerr , Daniel J. Klein , Mickaël Binois , Roman Garnett , Ross A. Hammond
Advances in computing power and data availability have led to growing sophistication in mechanistic mathematical models of social dynamics. Increasingly these models are used to inform real-world policy decision-making, often with significant time sensitivity. One such modeling approach is agent-based modeling, which offers particular strengths for capturing spatial and behavioral realism, and for in-silico experiments (varying input parameters and assumptions to explore their downstream impact on key outcomes). To be useful in the real-world, these models must be able to qualitatively or quantitatively capture observed empirical phenomena, forming the starting point for subsequent experimentation. One recent example is the COVID-19 pandemic, where epidemiological agent-based models informed policy and response planning worldwide. Throughout, modeling teams often had to spend valuable time and effort aligning their models to data, also known as calibration. Since many agent-based models are computationally intensive, the calibration process constrains the questions and scenarios policymakers may explore in time-sensitive situations. In this paper, we combine history matching, heteroskedastic Gaussian process modeling, and approximate Bayesian computation to address this bottleneck, substantially increasing efficiency and thus widening the range of utility for policy models. We illustrate our approach with a case study using a previously published and widely used epidemiological model, the Covasim model.
{"title":"Improving policy-oriented agent-based modeling with history matching: A case study","authors":"David O’Gara , Cliff C. Kerr , Daniel J. Klein , Mickaël Binois , Roman Garnett , Ross A. Hammond","doi":"10.1016/j.epidem.2025.100845","DOIUrl":"10.1016/j.epidem.2025.100845","url":null,"abstract":"<div><div>Advances in computing power and data availability have led to growing sophistication in mechanistic mathematical models of social dynamics. Increasingly these models are used to inform real-world policy decision-making, often with significant time sensitivity. One such modeling approach is agent-based modeling, which offers particular strengths for capturing spatial and behavioral realism, and for <em>in-silico</em> experiments (varying input parameters and assumptions to explore their downstream impact on key outcomes). To be useful in the real-world, these models must be able to qualitatively or quantitatively capture observed empirical phenomena, forming the starting point for subsequent experimentation. One recent example is the COVID-19 pandemic, where epidemiological agent-based models informed policy and response planning worldwide. Throughout, modeling teams often had to spend valuable time and effort aligning their models to data, also known as calibration. Since many agent-based models are computationally intensive, the calibration process constrains the questions and scenarios policymakers may explore in time-sensitive situations. In this paper, we combine history matching, heteroskedastic Gaussian process modeling, and approximate Bayesian computation to address this bottleneck, substantially increasing efficiency and thus widening the range of utility for policy models. We illustrate our approach with a case study using a previously published and widely used epidemiological model, the Covasim model.</div></div>","PeriodicalId":49206,"journal":{"name":"Epidemics","volume":"52 ","pages":"Article 100845"},"PeriodicalIF":3.0,"publicationDate":"2025-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144672567","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-07-14DOI: 10.1016/j.epidem.2025.100840
K. Ken Peng , Charmaine B. Dean , X. Joan Hu , Robert Delatolla
Recent research highlights a strong correlation between COVID-19 hospitalizations and wastewater viral signals. Increases in wastewater viral signals may be early warnings of increases in hospital admissions. That indicates a promising opportunity to assess and predict the burden of infectious diseases and has driven the widespread adoption and development of wastewater monitoring tools by public health organizations. Previous studies utilize distributed lag models to explore associations of COVID-19 hospitalizations with lagged SARS-CoV-2 wastewater viral signals. However, the conventional distributed lag models assume the duration time of the lag to be fixed, which is not always plausible. This paper presents Markov-modulated models with distributed lasting time, treating the duration of the lag as a random variable defined by a hidden process. We evaluate exposure effects over the duration time and estimate the distribution of the lasting time using the wastewater data and COVID-19 hospitalization records from Ottawa, Canada during June 2020 to November 2022. The different COVID-19 pandemic waves are accommodated in the statistical learning. Moreover, two strategies for comparing the associations over different time intervals are exemplified using the Ottawa data. Of note, the proposed Markov modulated models, an extension of distributed lag models, are potentially applicable to many different problems where the lag time is not fixed.
{"title":"Learning associations of COVID-19 hospitalizations with wastewater viral signals by Markov modulated models","authors":"K. Ken Peng , Charmaine B. Dean , X. Joan Hu , Robert Delatolla","doi":"10.1016/j.epidem.2025.100840","DOIUrl":"10.1016/j.epidem.2025.100840","url":null,"abstract":"<div><div>Recent research highlights a strong correlation between COVID-19 hospitalizations and wastewater viral signals. Increases in wastewater viral signals may be early warnings of increases in hospital admissions. That indicates a promising opportunity to assess and predict the burden of infectious diseases and has driven the widespread adoption and development of wastewater monitoring tools by public health organizations. Previous studies utilize distributed lag models to explore associations of COVID-19 hospitalizations with lagged SARS-CoV-2 wastewater viral signals. However, the conventional distributed lag models assume the duration time of the lag to be fixed, which is not always plausible. This paper presents Markov-modulated models with distributed lasting time, treating the duration of the lag as a random variable defined by a hidden process. We evaluate exposure effects over the duration time and estimate the distribution of the lasting time using the wastewater data and COVID-19 hospitalization records from Ottawa, Canada during June 2020 to November 2022. The different COVID-19 pandemic waves are accommodated in the statistical learning. Moreover, two strategies for comparing the associations over different time intervals are exemplified using the Ottawa data. Of note, the proposed Markov modulated models, an extension of distributed lag models, are potentially applicable to many different problems where the lag time is not fixed.</div></div>","PeriodicalId":49206,"journal":{"name":"Epidemics","volume":"52 ","pages":"Article 100840"},"PeriodicalIF":3.0,"publicationDate":"2025-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144666047","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-07-09DOI: 10.1016/j.epidem.2025.100844
Tianlong Yang , Xunbo Du , Junfan Li , Tin Zhang , Yao Wang , Liang Wang
Background
Scarlet fever (SF) is an acute infectious disease that poses a significant public health threat; however, its transmission dynamics, particularly the impact of asymptomatic carriers and socioeconomic determinants, remain unclear.
Methods
We developed a susceptible–exposed–infectious–asymptomatic–recovered (SEIAR) model that incorporates asymptomatic infections to estimate the time-varying reproduction number (Rt) for SF in Chengdu (2005–2019) using local epidemiological data. The model was evaluated using the coefficient of determination (R²), and sensitivity analysis confirmed its robustness. We further integrated Boruta, Extreme Gradient Boosting (XGBoost), and SHapley Additive exPlanations (SHAP) to systematically assess the influence of socioeconomic variables on Rt.
Results
Between 2005 and 2019, Chengdu reported 11,499 cases of SF, with an average incidence of 4.87 per 100,000. Two distinct seasonal peaks occurred in April–May and November–December, and incidence rates were notably lower during school holidays. The majority of cases affected children aged 3–7, with a male-to-female ratio of 1.59:1. In addition, core districts such as Wuhou and Xindu exhibited the highest incidence. The SEIAR model demonstrated strong predictive performance (overall R² = 0.831, P < 0.001) and estimated a median Rt of 0.963; however, several regions exceeded this threshold, with Rt peaking approximately two months prior to incidence surges. Spatial analyses revealed significant clustering in central urban areas, and integrated socioeconomic analysis identified the one-child rate as the primary driver of Rt, followed by population density and healthcare facility density (P < 0.01).
Conclusion
By integrating epidemiological data with socioeconomic factors, this study quantitatively elucidates the transmission characteristics of SF in Chengdu, providing data-driven support for monitoring and targeted intervention strategies in the absence of vaccination.
{"title":"Modeling transmission dynamics and socio-economic determinants of scarlet fever in Chengdu, China: An integrated SEIAR and machine learning approach","authors":"Tianlong Yang , Xunbo Du , Junfan Li , Tin Zhang , Yao Wang , Liang Wang","doi":"10.1016/j.epidem.2025.100844","DOIUrl":"10.1016/j.epidem.2025.100844","url":null,"abstract":"<div><h3>Background</h3><div>Scarlet fever (SF) is an acute infectious disease that poses a significant public health threat; however, its transmission dynamics, particularly the impact of asymptomatic carriers and socioeconomic determinants, remain unclear.</div></div><div><h3>Methods</h3><div>We developed a susceptible–exposed–infectious–asymptomatic–recovered (SEIAR) model that incorporates asymptomatic infections to estimate the time-varying reproduction number (<em>R</em><sub><em>t</em></sub>) for SF in Chengdu (2005–2019) using local epidemiological data. The model was evaluated using the coefficient of determination (<em>R</em>²), and sensitivity analysis confirmed its robustness. We further integrated Boruta, Extreme Gradient Boosting (XGBoost), and SHapley Additive exPlanations (SHAP) to systematically assess the influence of socioeconomic variables on <em>R</em><sub><em>t</em></sub>.</div></div><div><h3>Results</h3><div>Between 2005 and 2019, Chengdu reported 11,499 cases of SF, with an average incidence of 4.87 per 100,000. Two distinct seasonal peaks occurred in April–May and November–December, and incidence rates were notably lower during school holidays. The majority of cases affected children aged 3–7, with a male-to-female ratio of 1.59:1. In addition, core districts such as Wuhou and Xindu exhibited the highest incidence. The SEIAR model demonstrated strong predictive performance (overall <em>R</em>² = 0.831, <em>P</em> < 0.001) and estimated a median <em>R</em><sub><em>t</em></sub> of 0.963; however, several regions exceeded this threshold, with <em>R</em><sub><em>t</em></sub> peaking approximately two months prior to incidence surges. Spatial analyses revealed significant clustering in central urban areas, and integrated socioeconomic analysis identified the one-child rate as the primary driver of <em>R</em><sub><em>t</em></sub>, followed by population density and healthcare facility density (<em>P</em> < 0.01).</div></div><div><h3>Conclusion</h3><div>By integrating epidemiological data with socioeconomic factors, this study quantitatively elucidates the transmission characteristics of SF in Chengdu, providing data-driven support for monitoring and targeted intervention strategies in the absence of vaccination.</div></div>","PeriodicalId":49206,"journal":{"name":"Epidemics","volume":"52 ","pages":"Article 100844"},"PeriodicalIF":3.0,"publicationDate":"2025-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144597434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-07-01DOI: 10.1016/j.epidem.2025.100841
Hester Korthals Altes , Jan Van De Kassteele , Bram Wisse , Maria Xiridou , Albert Jan Van Hoek , Jacco Wallinga
The monitoring of work absenteeism can inform pandemic decision making, besides the surveillance of disease end-points like mortality and intensive care bed occupancy. For instance, high disease prevalence accompanied by elevated levels of absenteeism in the healthcare sector will increase the strain on the health care system, and may necessitate adaptation of the control measures. This highlights the need to assess the association between COVID-19 disease prevalence and absenteeism in relevant economic sectors. We initiated the comprehensive monitoring and analysis of work absenteeism and developed an autoregressive time series model which combined COVID-19 prevalence as measured through syndromic surveillance, with absenteeism across various economic activity sectors in the Netherlands. The analysis was updated regularly and shared with policy makers. Overall, prevalence of COVID-19-like illnesses was the most important contributor to variation in absenteeism over the period November 2020-May 2023, with absenteeism rates varying markedly between activity sectors. Of the sectors well-covered by the absenteeism database, the Education and Logistics sectors showed the greatest contribution of a seasonal pattern independent of COVID-19 to absenteeism.
{"title":"Work absenteeism across economic activity sectors and its association with COVID-19-like illness prevalence in the Netherlands, 2020–2023","authors":"Hester Korthals Altes , Jan Van De Kassteele , Bram Wisse , Maria Xiridou , Albert Jan Van Hoek , Jacco Wallinga","doi":"10.1016/j.epidem.2025.100841","DOIUrl":"10.1016/j.epidem.2025.100841","url":null,"abstract":"<div><div>The monitoring of work absenteeism can inform pandemic decision making, besides the surveillance of disease end-points like mortality and intensive care bed occupancy. For instance, high disease prevalence accompanied by elevated levels of absenteeism in the healthcare sector will increase the strain on the health care system, and may necessitate adaptation of the control measures. This highlights the need to assess the association between COVID-19 disease prevalence and absenteeism in relevant economic sectors. We initiated the comprehensive monitoring and analysis of work absenteeism and developed an autoregressive time series model which combined COVID-19 prevalence as measured through syndromic surveillance, with absenteeism across various economic activity sectors in the Netherlands. The analysis was updated regularly and shared with policy makers. Overall, prevalence of COVID-19-like illnesses was the most important contributor to variation in absenteeism over the period November 2020-May 2023, with absenteeism rates varying markedly between activity sectors. Of the sectors well-covered by the absenteeism database, the Education and Logistics sectors showed the greatest contribution of a seasonal pattern independent of COVID-19 to absenteeism.</div></div>","PeriodicalId":49206,"journal":{"name":"Epidemics","volume":"52 ","pages":"Article 100841"},"PeriodicalIF":3.0,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144572646","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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