scholarly journals Interventions targeting nonsymptomatic cases can be important to prevent local outbreaks: COVID-19 as a case-study

2020 ◽  
Author(s):  
F.A. Lovell-Read ◽  
S. Funk ◽  
U. Obolski ◽  
C.A. Donnelly ◽  
R.N. Thompson
Keyword(s):  
Infectious Disease ◽  
Optimal Strategy ◽  
Process Model ◽  
Branching Process ◽  
Host Population ◽  
Imported Cases ◽  
New Locations ◽  
Disease Epidemics ◽  
And Control

ABSTRACTBackgroundDuring infectious disease epidemics, a key question is whether cases travelling to new locations will trigger local outbreaks. The risk of this occurring depends on a range of factors, such as the transmissibility of the pathogen, the susceptibility of the host population and, crucially, the effectiveness of local surveillance in detecting cases and preventing onward spread. For many pathogens, presymptomatic and/or asymptomatic (together referred to here as nonsymptomatic) transmission can occur, making effective surveillance challenging. In this study, using COVID-19 as a case-study, we show how the risk of local outbreaks can be assessed when nonsymptomatic transmission can occur.MethodsWe construct a branching process model that includes nonsymptomatic transmission, and explore the effects of interventions targeting nonsymptomatic or symptomatic hosts when surveillance resources are limited. Specifically, we consider whether the greatest reductions in local outbreak risks are achieved by increasing surveillance and control targeting nonsymptomatic or symptomatic cases, or a combination of both.FindingsSeeking to increase surveillance of symptomatic hosts alone is typically not the optimal strategy for reducing outbreak risks. Adopting a strategy that combines an enhancement of surveillance of symptomatic cases with efforts to find and isolate nonsymptomatic hosts leads to the largest reduction in the probability that imported cases will initiate a local outbreak.InterpretationDuring epidemics of COVID-19 and other infectious diseases, effective surveillance for nonsymptomatic hosts can be crucial to prevent local outbreaks.

scholarly journals Interventions targeting non-symptomatic cases can be important to prevent local outbreaks: SARS-CoV-2 as a case study

2021 ◽  
Vol 18 (178) ◽  
pp. 20201014
Author(s):  
Francesca A. Lovell-Read ◽  
Sebastian Funk ◽  
Uri Obolski ◽  
Christl A. Donnelly ◽  
Robin N. Thompson
Keyword(s):  
Infectious Disease ◽  
Optimal Strategy ◽  
Process Model ◽  
Branching Process ◽  
Host Population ◽  
Imported Cases ◽  
New Locations ◽  
Disease Epidemics ◽  
And Control

During infectious disease epidemics, an important question is whether cases travelling to new locations will trigger local outbreaks. The risk of this occurring depends on the transmissibility of the pathogen, the susceptibility of the host population and, crucially, the effectiveness of surveillance in detecting cases and preventing onward spread. For many pathogens, transmission from pre-symptomatic and/or asymptomatic (together referred to as non-symptomatic) infectious hosts can occur, making effective surveillance challenging. Here, by using SARS-CoV-2 as a case study, we show how the risk of local outbreaks can be assessed when non-symptomatic transmission can occur. We construct a branching process model that includes non-symptomatic transmission and explore the effects of interventions targeting non-symptomatic or symptomatic hosts when surveillance resources are limited. We consider whether the greatest reductions in local outbreak risks are achieved by increasing surveillance and control targeting non-symptomatic or symptomatic cases, or a combination of both. We find that seeking to increase surveillance of symptomatic hosts alone is typically not the optimal strategy for reducing outbreak risks. Adopting a strategy that combines an enhancement of surveillance of symptomatic cases with efforts to find and isolate non-symptomatic infected hosts leads to the largest reduction in the probability that imported cases will initiate a local outbreak.

scholarly journals Demanding of Lassa Fever: Reducing its Risk as an Infectious Disease

2020 ◽  
Author(s):  
Abdullahi Tunde Aborode ◽  
Victor Adegbile Adesewa ◽  
Oni Ebenezer Ayomide ◽  
Samuel Ogunsola Olarenwaju
Keyword(s):  
Infectious Disease ◽  
Relevant Information ◽  
Lassa Fever ◽  
West African ◽  
Focal Points ◽  
The World ◽  
Lassa Fever Virus ◽  
Imported Cases ◽  
Proactive Measures ◽  
And Control

In recent years, Lassa fever has been announced as an infectious disease in the world, a few imported cases have been accounted for in various pieces of the world and there are developing worries of the possibilities of Lassa fever Virus as an organic weapon. Regardless of its assaulting impact, no substantial arrangement has been created to reduce the hazard of the ailment, about a large portion of 10 years after identifying it. A Review based on the documents from the literature search on PubMed, Scopus, Goggle Scholar and Science direct. Out of these, the final 16 articles that met the criteria were selected. Relevant information on epidemiology, the burden of management and control were obtained. Timely and effective containment of the Lassa fever disease in Lassa village four decades ago could have minimized the devastating effect and threats posed by this illness in the West African sub-region and indeed the entire globe. That was a hard lesson calling for much more proactive measures towards the eradication of the illness at primary, secondary, and tertiary levels of health care. Hence, the paper is aimed at appraising the threats associated with Lassa fever disease; its demands on curtailing the menace of the epidemic, and recommendations on important focal points.

scholarly journals Using a household-structured branching process to analyse contact tracing in the SARS-CoV-2 pandemic

2021 ◽  
Vol 376 (1829) ◽  
pp. 20200267
Author(s):  
Martyn Fyles ◽  
Elizabeth Fearon ◽  
Christopher Overton ◽  
Tom Wingfield ◽  
Graham F. Medley ◽  
...  
Keyword(s):  
Process Model ◽  
Branching Process ◽  
Household Structure ◽  
Contact Tracing ◽  
Symptom Report ◽  
Primary Model ◽  
Imported Cases ◽  
Strategic Implementation ◽  
Household Members ◽  
The Uk

We explore strategies of contact tracing, case isolation and quarantine of exposed contacts to control the SARS-CoV-2 epidemic using a branching process model with household structure. This structure reflects higher transmission risks among household members than among non-household members. We explore strategic implementation choices that make use of household structure, and investigate strategies including two-step tracing, backwards tracing, smartphone tracing and tracing upon symptom report rather than test results. The primary model outcome is the effect of contact tracing, in combination with different levels of physical distancing, on the growth rate of the epidemic. Furthermore, we investigate epidemic extinction times to indicate the time period over which interventions must be sustained. We consider effects of non-uptake of isolation/quarantine, non-adherence, and declining recall of contacts over time. Our results find that, compared to self-isolation of cases without contact tracing, a contact tracing strategy designed to take advantage of household structure allows for some relaxation of physical distancing measures but cannot completely control the epidemic absent of other measures. Even assuming no imported cases and sustainment of moderate physical distancing, testing and tracing efforts, the time to bring the epidemic to extinction could be in the order of months to years. This article is part of the theme issue ‘Modelling that shaped the early COVID-19 pandemic response in the UK’.

scholarly journals Using a household structured branching process to analyse contact tracing in the SARS-CoV-2 pandemic

2021 ◽  
Author(s):  
Martyn Fyles ◽  
Elizabeth Fearon ◽  
Christopher Overton ◽  
Tom Wingfield ◽  
Graham F Medley ◽  
...  
Keyword(s):  
Process Model ◽  
Branching Process ◽  
Household Structure ◽  
Contact Tracing ◽  
Test Results ◽  
Symptom Report ◽  
Time Period ◽  
Primary Model ◽  
Imported Cases ◽  
Household Members

AbstractWe explore strategies of contact tracing, case isolation and quarantine of exposed contacts to control the SARS-CoV-2 epidemic using a branching process model with household structure. This structure reflects higher transmission risks among household members than among non-household members, and is also the level at which physical distancing policies have been applied. We explore implementation choices that make use of household structure, and investigate strategies including two-step tracing, backwards tracing, smartphone tracing and tracing upon symptom report rather than test results. The primary model outcome is the effect on the growth rate of the epidemic under contact tracing in combination with different levels of physical distancing, and we investigate epidemic extinction times to indicate the time period over which interventions must be sustained. We consider effects of non-uptake of isolation/quarantine, non-adherence, and declining recall of contacts over time. We find that compared to self-isolation of cases but no contact tracing, a household-based contact tracing strategy allows for some relaxation of physical distancing measures; however, it is unable to completely control the epidemic in the absence of other measures. Even assuming no imported cases and sustainment of moderate distancing, testing and tracing efforts, the time to bring the epidemic to extinction could be in the order of months to years.

scholarly journals A Branching Process Model for the Novel Coronavirus (Covid-19) Spread in Greece

2021 ◽  
pp. 63-69
Author(s):  
Ioanna A. Mitrofani ◽  
◽  
Vasilis P. Koutras
Keyword(s):  
Process Model ◽  
Branching Process ◽  
Early Stage ◽  
Branching Processes ◽  
Relevant Literature ◽  
Control Measures ◽  
The Novel ◽  
Simple Exponential Smoothing ◽  
Novel Coronavirus ◽  
And Control

The novel coronavirus (covid-19) was initially identified at the end of 2019 and caused a global health care crisis. The increased transmissibility of the virus, that led to high mortality, raises the interest of scientists worldwide. Thus, various methods and models have been extensively discussed, so to study and control covid-19 transmission. Mathematical modeling constitutes an important tool to estimate key parameters of the transmission and predict the dynamic of the virus. More precisely, in the relevant literature, epidemiology is considered as a classical application area of branching processes, which are stochastic individual-based processes. In this paper, we develop a classical Galton-Watson branching process approach for the covid-19 spread in Greece at the early stage. This approach is structured in two parts, initial and latter transmission stages, so to provide a comprehensive view of the virus spread through basic and effective reproduction numbers respectively, along with the probability of an outbreak. Additionally, the effectiveness of control measures is discussed, based on a simple exponential smoothing model, which is used to build a non-mitigation scenario. Finally, our primary aim is to model all transmission stages through branching processes in order to analyze the first semiannual spread of the ongoing coronavirus pandemic in the region of Greece.

scholarly journals The Probability of Containment for Multitype Branching Process Models for Emerging Epidemics

2011 ◽  
Vol 48 (1) ◽  
pp. 173-188
Author(s):  
Simon E. F. Spencer ◽  
Philip D. O‘Neill
Keyword(s):  
Infectious Disease ◽  
Multiple Solutions ◽  
Branching Process ◽  
Specific Model ◽  
Process Models ◽  
Multitype Branching Process ◽  
Fixed Point Equation ◽  
Point Equation ◽  
Disease Epidemics ◽  
Special Case

This paper is concerned with the definition and calculation of containment probabilities for emerging disease epidemics. A general multitype branching process is used to model an emerging infectious disease in a population of households. It is shown that the containment probability satisfies a certain fixed point equation which has a unique solution under certain conditions; the case of multiple solutions is also described. The extinction probability of the branching process is shown to be a special case of the containment probability. It is shown that Laplace transform ordering of the severity distributions of households in different epidemics yields an ordering on the containment probabilities. The results are illustrated with both standard epidemic models and a specific model for an emerging strain of influenza.

scholarly journals The Probability of Containment for Multitype Branching Process Models for Emerging Epidemics

2011 ◽  
Vol 48 (01) ◽  
pp. 173-188
Author(s):  
Simon E. F. Spencer ◽  
Philip D. O‘Neill
Keyword(s):  
Infectious Disease ◽  
Multiple Solutions ◽  
Branching Process ◽  
Specific Model ◽  
Process Models ◽  
Multitype Branching Process ◽  
Fixed Point Equation ◽  
Point Equation ◽  
Disease Epidemics ◽  
Special Case

This paper is concerned with the definition and calculation of containment probabilities for emerging disease epidemics. A general multitype branching process is used to model an emerging infectious disease in a population of households. It is shown that the containment probability satisfies a certain fixed point equation which has a unique solution under certain conditions; the case of multiple solutions is also described. The extinction probability of the branching process is shown to be a special case of the containment probability. It is shown that Laplace transform ordering of the severity distributions of households in different epidemics yields an ordering on the containment probabilities. The results are illustrated with both standard epidemic models and a specific model for an emerging strain of influenza.

scholarly journals Detection, forecasting and control of infectious disease epidemics: modelling outbreaks in humans, animals and plants

2019 ◽  
Vol 374 (1775) ◽  
pp. 20190038 ◽  
Author(s):  
Robin N. Thompson ◽  
Ellen Brooks-Pollock
Keyword(s):  
Infectious Disease ◽  
Decision Making ◽  
Plant Disease ◽  
Influenza Pandemic ◽  
Disease Outbreaks ◽  
Theme Issue ◽  
Infectious Disease Outbreaks ◽  
Human Animal ◽  
Disease Epidemics ◽  
And Control

The 1918 influenza pandemic is one of the most devastating infectious disease epidemics on record, having caused approximately 50 million deaths worldwide. Control measures, including prohibiting non-essential gatherings as well as closing cinemas and music halls, were applied with varying success and limited knowledge of transmission dynamics. One hundred years later, following developments in the field of mathematical epidemiology, models are increasingly used to guide decision-making and devise appropriate interventions that mitigate the impacts of epidemics. Epidemiological models have been used as decision-making tools during outbreaks in human, animal and plant populations. However, as the subject has developed, human, animal and plant disease modelling have diverged. Approaches have been developed independently for pathogens of each host type, often despite similarities between the models used in these complementary fields. With the increased importance of a One Health approach that unifies human, animal and plant health, we argue that more inter-disciplinary collaboration would enhance each of the related disciplines. This pair of theme issues presents research articles written by human, animal and plant disease modellers. In this introductory article, we compare the questions pertinent to, and approaches used by, epidemiological modellers of human, animal and plant pathogens, and summarize the articles in these theme issues. We encourage future collaboration that transcends disciplinary boundaries and links the closely related areas of human, animal and plant disease epidemic modelling. This article is part of the theme issue ‘Modelling infectious disease outbreaks in humans, animals and plants: approaches and important themes’. This issue is linked with the subsequent theme issue ‘Modelling infectious disease outbreaks in humans, animals and plants: epidemic forecasting and control’.

scholarly journals Dynamic of a TB-HIV Coinfection Epidemic Model with Latent Age

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Xiaoyan Wang ◽  
Junyuan Yang ◽  
Fengqin Zhang
Keyword(s):  
Infectious Disease ◽  
Human Immunodeficiency Virus ◽  
Latent Tuberculosis ◽  
Host Population ◽  
The Other ◽  
Hiv Coinfection ◽  
Immunodeficiency Virus ◽  
Latent Tb ◽  
Disease Epidemics ◽  
Disease Free

A coepidemic arises when the spread of one infectious disease stimulates the spread of another infectious disease. Recently, this has happened with human immunodeficiency virus (HIV) and tuberculosis (TB). The density of individuals infected with latent tuberculosis is structured by age since latency. The host population is divided into five subclasses of susceptibles, latent TB, active TB (without HIV), HIV infectives (without TB), and coinfection class (infected by both TB and HIV). The model exhibits three boundary equilibria, namely, disease free equilibrium, TB dominated equilibrium, and HIV dominated equilibrium. We discuss the local or global stabilities of boundary equilibria. We prove the persistence of our model. Our simple model of two synergistic infectious disease epidemics illustrates the importance of including the effects of each disease on the transmission and progression of the other disease. We simulate the dynamic behaviors of our model and give medicine explanations.

Capstan Design and Control for Drawing Optical Fiber: A Case Study in Mechatronics Design

2007 ◽  
Author(s):  
Hodge E. Jenkins ◽  
Mark L. Nagurka
Keyword(s):  
Optical Fiber ◽  
Process Model ◽  
Systems Approach ◽  
Fiber Diameter ◽  
Fiber Quality ◽  
Optical Data ◽  
Glass Temperature ◽  
Simulation Studies ◽  
And Control

This paper presents a case study on the design of a draw capstan drive with feedback control for use in optical fiber manufacturing. Optical fiber is manufactured by the draw process, which involves heating and pulling high purity glass cylinders to diameters of 125 micron. Of critical concern is producing a constant diameter for the glass fiber and its lightguide core. The diameter of the optical fiber must remain constant to create a product capable of transmitting high-bandwidth optical data. The optical fiber draw capstan design has a significant impact on the resulting fiber quality. As the draw speed is used to control the fiber diameter, the ability of the draw capstan to follow velocity commands directly affects the resulting fiber diameter. In this case study a systems approach is used for the design of the mechanical and control aspects through parametric evaluations and modeling, as well as simulation studies of the capstan drive. Disturbances in the draw process arise from sources such as the variation in the diameter of the input glass cylinder and the draw tension control, affecting the glass temperature and viscosity. Simulation studies demonstrate that speed regulation, to manufacture optical fiber within allowable diameter tolerances, is achievable in the presence of representative disturbances. The capstan model and design along with the fiberdrawing process model presented in this case study are suitable for undergraduate and graduate courses in system dynamics, control, and mechatronics. As is typical of many problems in manufacturing processes, the problem discussed is multidisciplinary. The study highlights the use of mechanical and electrical modeling, system identification, and control design as necessary parts of product and process improvement.

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