scholarly journals A renewal equation model to assess roles and limitations of contact tracing for disease outbreak control

2021 ◽  
Vol 8 (4) ◽  
Author(s):  
Francesca Scarabel ◽  
Lorenzo Pellis ◽  
Nicholas H. Ogden ◽  
Jianhong Wu
Keyword(s):  
Deterministic Model ◽  
Infected Individual ◽  
Equation Model ◽  
Renewal Equation ◽  
Contact Tracing ◽  
Calendar Time ◽  
Individual Level ◽  
Total Incidence ◽  
Community Transmission ◽  
The Individual

We propose a deterministic model capturing essential features of contact tracing as part of public health non-pharmaceutical interventions to mitigate an outbreak of an infectious disease. By incorporating a mechanistic formulation of the processes at the individual level, we obtain an integral equation (delayed in calendar time and advanced in time since infection) for the probability that an infected individual is detected and isolated at any point in time. This is then coupled with a renewal equation for the total incidence to form a closed system describing the transmission dynamics involving contact tracing. We define and calculate basic and effective reproduction numbers in terms of pathogen characteristics and contact tracing implementation constraints. When applied to the case of SARS-CoV-2, our results show that only combinations of diagnosis of symptomatic infections and contact tracing that are almost perfect in terms of speed and coverage can attain control, unless additional measures to reduce overall community transmission are in place. Under constraints on the testing or tracing capacity, a temporary interruption of contact tracing may, depending on the overall growth rate and prevalence of the infection, lead to an irreversible loss of control even when the epidemic was previously contained.

scholarly journals A renewal equation model to assess roles and limitations of contact tracing for disease outbreak control

2021 ◽  
Author(s):  
Francesca Scarabel ◽  
Lorenzo Pellis ◽  
Nicholas H Ogden ◽  
Jianhong Wu
Keyword(s):  
Deterministic Model ◽  
Infected Individual ◽  
Equation Model ◽  
Renewal Equation ◽  
Contact Tracing ◽  
Calendar Time ◽  
Individual Level ◽  
Total Incidence ◽  
Community Transmission ◽  
The Individual

We propose a deterministic model capturing essential features of contact tracing as part of public health non-pharmaceutical interventions to mitigate an outbreak of an infectious disease. By incorporating a mechanistic formulation of the processes at the individual level, we obtain an integral equation (delayed in calendar time and advanced in time since infection) for the probability that an infected individual is detected and isolated at any point in time. This is then coupled with a renewal equation for the total incidence to form a closed system describing the transmission dynamics involving contact tracing. We define and calculate basic and effective reproduction numbers in terms of pathogen characteristics and contact tracing implementation constraints. When applied to the case of SARS-CoV-2, our results show that only combinations of diagnosis of symptomatic infections and contact tracing that are almost perfect in terms of speed and coverage can attain control, unless additional measures to reduce overall community transmission are in place. Under constraints on the testing or tracing capacity, a temporary interruption of contact tracing may, depending on the overall growth rate and prevalence of the infection, lead to an irreversible loss of control even when the epidemic was previously contained.

A STOCHASTIC MODEL FOR EPIDEMICS BASED ON THE RENEWAL EQUATION

2000 ◽  
Vol 08 (01) ◽  
pp. 1-20 ◽  
Author(s):  
J. L. W. GIELEN
Keyword(s):  
Stochastic Model ◽  
Deterministic Model ◽  
Formal Solution ◽  
Infected Individual ◽  
External Source ◽  
Mean Value ◽  
Renewal Equation ◽  
Infection Model ◽  
Final Size ◽  
Infinite Population

A stochastic continuous-infection model is developed that describes the evolution of an infectious disease introduced into an infinite population of susceptibles. The proposed model is the natural stochastic counterpart of the deterministic model for epidemics, based on the renewal equation. As in the deterministic model, the infectivity of an infected individual is a function of his age-of-infection, that is the time elapsed since his own infection. A time-dependent external source of infection is included. The model provides analytical expressions that describe the stochastic infective-age structure of the population at any moment of time. It is shown that the mean value of the number of infectives predicted by the stochastic model satisfies the renewal equation, which furnishes a formal solution of this equation. The model also yields simple expressions for the expected arrival times of infectives, that can be useful for the inverse problem. An explicit expression for the final size distribution is obtained. This leads to a precise quantitative threshold theorem that distinguishes between the possibilities of a minor outbreak or a major build-up of the epidemic.

scholarly journals If You Believe, It May Come True: The Relationship and Mechanism Between Self-Occupation Stereotypes of Private Kindergarten Teachers and Their Turnover Intention in China-Mainland

2021 ◽  
Vol 12 ◽  
Author(s):  
Feng Yang ◽  
Yang Han ◽  
Minyan Li
Keyword(s):  
Professional Identity ◽  
Turnover Intention ◽  
Personal Control ◽  
Equation Model ◽  
Kindergarten Teachers ◽  
Individual Level ◽  
Occupation Stereotypes ◽  
The Individual ◽  
China Mainland ◽  
The Relationship

In China-Mainland, the turnover rate of private kindergarten teachers remains high for a long time. With 692 Chinese private kindergarten teachers as subjects, we applied a questionnaire survey to examine the relationship between self-occupation stereotypes held by private kindergarten teachers and their turnover intention and the underlying mechanisms. The structured equation model (SCM) was conducted to analyze data and revealed a significantly positive correlation between self-occupation stereotypes and turnover intention. Further analyses showed that on the individual level, personal control sense mediated the relationship between self-occupation stereotypes and turnover intention, and on the organization level, professional identity mediated the relationship between them. Additionally, self-occupation stereotypes were also related to turnover intention via the chain-mediating role of personal control sense and professional identity. The current research firstly clarified the acting paths between self-occupation stereotypes of private kindergarten teachers and turnover intention on both the individual and the organization levels. In practice, the research provided a novel perspective for policy makers to alleviate the turnover tendency of private kindergarten teachers.

scholarly journals The Impact of Universal Mask Use on SARS-COV-2 in Victoria, Australia on the Epidemic Trajectory of COVID-19

2021 ◽  
Vol 9 ◽  
Author(s):  
Valentina Costantino ◽  
Chandini Raina MacIntyre
Keyword(s):  
Mathematical Modeling ◽  
Deterministic Model ◽  
Face Mask ◽  
Control Measures ◽  
Contact Tracing ◽  
Epidemic Size ◽  
Community Transmission ◽  
Age Structured ◽  
The Impact ◽  
Mask Effectiveness

Objective(s): To estimate the impact of universal community face mask use in Victoria, Australia along with other routine disease control measures in place.Methods: A mathematical modeling study using an age structured deterministic model for Victoria, was simulated for 123 days between 1 June 2020 and 1 October 2020, incorporating lockdown, contact tracing, and case findings with and without mask use in varied scenarios. The model tested the impact of differing scenarios of the universal use of face masks in Victoria, by timing, varying mask effectiveness, and uptake.Results: A six-week lockdown with standard control measures, but no masks, would have resulted in a large resurgence by September, following the lifting of restrictions. Mask use can substantially reduce the epidemic size, with a greater impact if at least 50% of people wear a mask which has an effectiveness of at least 40%. Early mask use averts more cases than mask usage that is only implemented closer to the peak. No mask use, with a 6-week lockdown, results in 67,636 cases and 120 deaths by 1 October 2020 if no further lockdowns are used. If mask use at 70% uptake commences on 23 July 2020, this is reduced to 7,961 cases and 42 deaths. We estimated community mask effectiveness to be 11%.Conclusion(s): Lockdown and standard control measures may not have controlled the epidemic in Victoria. Mask use can substantially improve epidemic control if its uptake is higher than 50% and if moderately effective masks are used. Early mask use should be considered in other states if community transmission is present, as this has a greater effect than later mask wearing mandates.

scholarly journals Testing, tracing and isolation in compartmental models

2021 ◽  
Vol 17 (3) ◽  
pp. e1008633
Author(s):  
Simone Sturniolo ◽  
William Waites ◽  
Tim Colbourn ◽  
David Manheim ◽  
Jasmina Panovska-Griffiths
Keyword(s):  
Computational Cost ◽  
Disease Outbreaks ◽  
Population Level ◽  
Compartmental Models ◽  
Contact Tracing ◽  
Adaptive Planning ◽  
Agent Based ◽  
Individual Level ◽  
Individual Based Models ◽  
The Individual

Existing compartmental mathematical modelling methods for epidemics, such as SEIR models, cannot accurately represent effects of contact tracing. This makes them inappropriate for evaluating testing and contact tracing strategies to contain an outbreak. An alternative used in practice is the application of agent- or individual-based models (ABM). However ABMs are complex, less well-understood and much more computationally expensive. This paper presents a new method for accurately including the effects of Testing, contact-Tracing and Isolation (TTI) strategies in standard compartmental models. We derive our method using a careful probabilistic argument to show how contact tracing at the individual level is reflected in aggregate on the population level. We show that the resultant SEIR-TTI model accurately approximates the behaviour of a mechanistic agent-based model at far less computational cost. The computational efficiency is such that it can be easily and cheaply used for exploratory modelling to quantify the required levels of testing and tracing, alone and with other interventions, to assist adaptive planning for managing disease outbreaks.

scholarly journals Stock Market Anomalies as Mediators Between Prospect Factors and Investment Decisions and Performance: Findings at the Individual Investor Level

2017 ◽  
Vol 6 (1) ◽  
pp. 21-40
Author(s):  
Syed Zain Ul Abdin ◽  
Naheed Sultana ◽  
Mariam Farooq ◽  
Syed Zulfiqar Ali Shah
Keyword(s):  
Structural Equation ◽  
Investment Decisions ◽  
Equation Model ◽  
Individual Investors ◽  
Market Anomalies ◽  
Individual Level ◽  
Calendar Anomalies ◽  
And Performance ◽  
The Individual ◽  
Regret Aversion

While other studies have investigated the direct impact of prospect factors on investment decisions and performance at the individual level, we examine the mediated link between the two, via fundamental, technical and calendar anomalies. The study applies a structural equation model to data for 324 individual investors in Pakistan. Our findings show that two processes, fundamental and calendar anomalies, mediate the relationship between certain prospect factors and investment decisions and performance. Of these prospect factors, regret aversion is the strongest predictor of investment decisions and performance, followed by calendar anomalies. It is also the strongest predictor of investment decisions and performance via fundamental anomalies.

scholarly journals Analysis of Individual-Level Epidemic Data: Study of 2018-2020 Ebola Outbreak in Democratic Republic of the Congo

2021 ◽  
Author(s):  
Harley Vossler ◽  
Pierre Akilimali ◽  
Yuhan Pan ◽  
Wasiur Khudabukhsh ◽  
Eben Kenah ◽  
...  
Keyword(s):  
At Risk ◽  
Ebola Virus ◽  
Democratic Republic ◽  
Virus Disease ◽  
Contact Tracing ◽  
Effective Population ◽  
Individual Level ◽  
Ring Vaccination ◽  
Republic Of The Congo ◽  
The Individual

Abstract The 2018-2020 Ebola virus disease epidemic in Democratic Republic of the Congo (DRC) resulted in 3481 cases (probable and confirmed) and 2299 deaths. In this paper, we use a novel statistical method to analyze the individual-level incidence and hospitalization data on DRC Ebola victims. Our analysis suggests that an increase in the rate of quarantine and isolation by approximately 12% during the epidemic’s third and final wave was likely responsible for the eventual containment of the outbreak. The analysis further reveals that the total effective population size or the average number of individuals at risk for the disease exposure in three epidemic waves over the period of 24 months was around 19,000—a much smaller number than previously estimated and likely an evidence of at least partial protection of the population at risk through ring vaccination and contact tracing as well as adherence to strict quarantine and isolation policies.

scholarly journals Pruning Digital Contact Networks for Meso-scale Epidemic Surveillance Using Foursquare Data

2021 ◽  
Author(s):  
Sofia Hurtado ◽  
Radu Marculescu ◽  
Justin A. Drake ◽  
Ravi Srinivasan
Keyword(s):  
New York ◽  
Human Mobility ◽  
Smart Phone ◽  
Population Level ◽  
Dynamic Contact ◽  
Contact Tracing ◽  
Contact Networks ◽  
Individual Level ◽  
The Individual ◽  
Meso Scale

AbstractWith the recent boom in human sensing, the push to incorporate human mobility tracking with epidemic modeling highlights the lack of groundwork at the meso-scale (e.g., city-level) for both contact tracing and transmission dynamics. Although GPS data has been used to study city-level outbreaks, current approaches fail to capture the path of infection at the individual level. Consequently, in this paper, we extend the usefulness of epidemics prediction from estimating the size of an outbreak at the population level to estimating the individuals who may likely get infected within a finite period of time. To this end, we propose a network-based method to first build and then prune the dynamic contact networks for recurring interactions; these networks can serve as the backbone topology for mechanistic epidemics modeling. We test our method using Foursquare’s Points of Interest (POI) smart-phone geolocation data from over 1.3 million devices and show that we can recreate the COVID-19 infection curves for two major (yet very different) US cities (i.e., Austin and New York City) while maintaining the granularity of individual transmissions and reducing model uncertainty. Our method provides a foundation for building a disease prediction framework at the meso-scale that can help both policy makers and individuals of their estimated state of health and help with pandemic planning.

Thought self-leadership strategies and sales performance: integrating selling skills and adaptive selling behavior as missing links

2017 ◽  
Vol 32 (5) ◽  
pp. 652-663 ◽  
Author(s):  
Rakesh Singh ◽  
Narendra Kumar ◽  
Sandeep Puri
Keyword(s):  
Self Efficacy ◽  
Structural Equation ◽  
Sales Performance ◽  
Sales Force ◽  
Equation Model ◽  
Content Type ◽  
Adaptive Selling ◽  
Individual Level ◽  
Adaptive Selling Behavior ◽  
The Individual

Purpose This study aims to address the need to study salespersons’ thought self-leadership (TSL) and its effectiveness through the interplay of self-efficacy, skills and behavior at the individual level. It also advances the agenda of integrating self-leadership into marketing literature. Design/methodology/approach A model was tested using survey data collected from salespeople within pharmaceutical companies located in India and other Asian countries. A structural equation model was used to test the hypotheses. Findings The results suggest an interesting interplay between a salesperson’s TSL and his/her sales performance. The results also demonstrate the relationship between TSL and self-efficacy and the mediation mechanism through which self-efficacy influences sales performance. Results support the role of TSL as a distal predictor of performance and delineate the complexity of the mediation mechanism through theoretical grounding and empirical evidence. Research limitations/implications The research suggests that a salesperson’s TSL relates positively with the sales performance through three process variables; self-efficacy, selling skills and adaptive selling behavior. The results should encourage managers to leverage salesperson’s TSL strategies to build a self-leading sales force and optimize supervision cost. Moreover, training the sales force for enhanced TSL has immediate payoffs in terms of increased selling effectiveness. The study also discusses theoretical implications. Originality/value By examining TSL in the sales context, the study makes an original contribution to the extant literature. The results of the study enrich the extant information on self-leadership and sales performance linkages by suggesting a mediation mechanism and proposing an integrated framework with selling skills and adaptive selling behavior.

scholarly journals Incomplete protection against dengue virus type 2 re-infection in Peru

2015 ◽  
Author(s):  
Brett M. Forshey ◽  
Robert C. Reiner ◽  
Sandra Olkowski ◽  
Amy C. Morrison ◽  
Angelica Espinoza ◽  
...  
Keyword(s):  
Confidence Interval ◽  
Dengue Virus ◽  
Neutralizing Antibodies ◽  
Age Distribution ◽  
Neutralizing Antibody ◽  
Denv Infection ◽  
Contact Tracing ◽  
Individual Level ◽  
The Individual

Background. Nearly half of the world’s population is at risk for dengue, yet no licensed vaccine or anti-viral drug is currently available. Dengue is caused by any of four dengue virus serotypes (DENV-1 through DENV-4), and infection by a DENV serotype is assumed to provide life-long protection against re-infection by that serotype. We investigated the validity of this fundamental assumption during a large dengue epidemic caused by DENV-2 in Iquitos, Peru, in 2010-2011, 15 years after the first outbreak of DENV-2 in the region.Methodology/Principal Findings. We estimated the age-dependent prevalence of serotype-specific DENV antibodies from longitudinal cohort studies conducted between 1993 and 2010. During the 2010-2011 epidemic, active dengue cases were identified through active community- and clinic-based febrile surveillance studies, and acute inapparent DENV infections were identified through contact tracing studies. Based on the age-specific prevalence of DENV-2 neutralizing antibodies, the age distribution of DENV-2 cases was markedly older than expected. Homologous protection was estimated at 35.1% (95% confidence interval: 0% -- 65.2%). At the individual level, pre-existing DENV-2 antibodies were associated with an incomplete reduction in the frequency of symptoms. Among dengue cases, 43% (26/66) exhibited elevated DENV-2 neutralizing antibody titers for years prior to infection, compared with 76% (13/17) of inapparent infections (age-adjusted odds ratio: 4.2; 95% confidence interval: 1.1 – 17.7).Conclusions/Significance. Our data indicate that protection from homologous DENV re-infection may be incomplete in some circumstances, which provides context for the limited vaccine efficacy against DENV-2 in recent trials. Further studies are warranted to confirm this phenomenon and to evaluate the potential role of incomplete homologous protection in DENV transmission dynamics.Author SummaryHomotypic immunity against DENV infection has been assumed to be complete and lifelong, and to our knowledge, instances of homologous DENV re-infection have not been rigorously documented. However, few long-term studies have been conducted in such a way that homologous re-infection could be observed, if it did in fact occur. Our study provides evidence that homologous re-infection may occur in certain circumstances. We draw from data collected during a 2010-2011 DENV-2 epidemic in northeastern Peru, 15 years after the initial DENV-2 outbreak in the region. This finding has significant implications for our understanding of dengue epidemiology and for dengue vaccine formulation, which may need to consider multiple genotypes of each serotype. Data from other long-term dengue epidemiology studies should be analyzed to determine of homologous re-infection is a more widespread phenomenon.

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