scholarly journals Immunologic and epidemiologic drivers of norovirus transmission in daycare and school outbreaks

2019 ◽  
Author(s):  
Joshua Havumaki ◽  
Joseph NS Eisenberg ◽  
Claire P Mattison ◽  
Benjamin A Lopman ◽  
Ismael R Ortega-Sanchez ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Surveillance Data ◽  
Control Measures ◽  
Disease Spread ◽  
Transmission Model ◽  
Level Control ◽  
School Settings ◽  
Population Immunity ◽  
Contact Rates ◽  
Disease Transmission Model

1AbstractBackgroundNorovirus outbreaks are notoriously explosive, with dramatic symptomology and rapid disease spread. Children are particularly vulnerable to infection and drive norovirus transmission due to their high contact rates with each other and the environment. Despite the explosive nature of norovirus outbreaks, attack rates in schools and daycares remain low with the majority of students not reporting symptoms.MethodsWe explore immunologic and epidemiologic mechanisms that may underlie epidemic norovirus transmission dynamics using a disease transmission model. Towards this end, we compared different model scenarios, including innate resistance and acquired immunity (collectively denoted ‘immunity’), stochastic extinction, and an individual exclusion intervention. We calibrated our model to daycare and school outbreaks from national surveillance data.ResultsRecreating the low attack rates observed in daycare and school outbreaks required a model with immunity. However, immunity alone resulted in shorter duration outbreaks than what was observed. The addition of individual exclusion (to the immunity model) extended outbreak durations by reducing the amount of time that symptomatic people contribute to transmission. Including both immunity and individual exclusion mechanisms resulted in simulations where both attack rates and outbreak durations were consistent with surveillance data.ConclusionsThe epidemiology of norovirus outbreaks in daycare and school settings cannot be well described by a simple transmission model in which all individuals start as fully susceptible. Interventions should leverage population immunity and encourage more rigorous individual exclusion to improve venue-level control measures.

scholarly journals Scenario Tree and Adaptive Decision Making on Optimal Type and Timing for Intervention and Social-economic Activity Changes to Manage the COVID-19 Pandemic

2020 ◽  
Vol 13 (3) ◽  
pp. 710-729
Author(s):  
Kyeongah Nah ◽  
Shengyuan Chen ◽  
Yanyu Xiao ◽  
Biao Tang ◽  
Nicola Bragazzi ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Optimization Technique ◽  
System Capacity ◽  
Scenario Tree ◽  
Transmission Model ◽  
Optimal Timing ◽  
Contact Rates ◽  
Novel Approach ◽  
Disease Transmission Model ◽  
Adaptive Decision Making

We introduce a novel approach to inform the re-opening plan followed by a postpandemic lockdown by integrating a stochastic optimization technique with a disease transmission model. We assess Ontarios re-opening plans as a case-study. Taking into account the uncertainties in contact rates during different re-opening phases, we find the optimal timing for the upcoming re-opening phase that maximizes the relaxation of social contacts under uncertainties, while not overwhelming the health system capacity before the arrival of effective therapeutics or vaccines.

scholarly journals Predicting the Time to Detect Moderately Virulent African Swine Fever Virus in Finisher Swine Herds Using a Stochastic Disease Transmission Model

2021 ◽  
Author(s):  
Sasidhar Malladi ◽  
Amos Ssematimba ◽  
Peter J. Bonney ◽  
Kaitlyn M. St. Charles ◽  
Timothy Boyer ◽  
...  
Keyword(s):  
Disease Transmission ◽  
African Swine Fever Virus ◽  
Clinical Signs ◽  
African Swine Fever ◽  
The United States ◽  
Disease Spread ◽  
Transmission Model ◽  
Economic Losses ◽  
Parameter Estimates ◽  
Disease Transmission Model

Abstract Background: African swine fever (ASF) is a highly contagious and devastating pig disease that has caused extensive global economic losses. Understanding ASF virus (ASFV) transmission dynamics within a herd is necessary in order to prepare for and respond to an outbreak in the United States. Although the transmission parameters for the highly virulent ASF strains have been estimated in several articles, there are relatively few studies focused on moderately virulent strains. Using an approximate Bayesian computation algorithm in conjunction with Monte Carlo simulation, we have estimated the adequate contact rate for moderately virulent ASFV strains and determined the statistical distributions for the durations of mild and severe clinical signs using individual, pig-level data. A discrete individual based disease transmission model was then used to estimate the time to detect ASF infection based on increased mild clinical signs, severe clinical signs, or daily mortality. Results: Our results indicate that it may take two weeks or longer to detect ASF in a finisher swine herd via mild clinical signs or increased mortality beyond levels expected in routine production. A key factor contributing to the extended time to detect ASF in a herd is the fairly long latently infected period for an individual pig (mean 4.5, 95% P.I., 2.4 - 7.2 days). Conclusion: These transmission model parameter estimates and estimated time to detection via clinical signs provide valuable information that can be used not only to support emergency preparedness but also to inform other simulation models of evaluating regional disease spread.

Lyapunov functions for a dengue disease transmission model

2009 ◽  
Vol 39 (2) ◽  
pp. 936-941 ◽  
Author(s):  
Jean Jules Tewa ◽  
Jean Luc Dimi ◽  
Samuel Bowong
Keyword(s):  
Disease Transmission ◽  
Lyapunov Functions ◽  
Transmission Model ◽  
Dengue Disease ◽  
Disease Transmission Model

scholarly journals Differential effects of intervention timing on COVID-19 spread in the United States

2020 ◽  
Vol 6 (49) ◽  
pp. eabd6370 ◽  
Author(s):  
Sen Pei ◽  
Sasikiran Kandula ◽  
Jeffrey Shaman
Keyword(s):  
United States ◽  
Disease Transmission ◽  
Human Mobility ◽  
The United States ◽  
Control Measures ◽  
Basic Reproductive Number ◽  
Transmission Model ◽  
Reproductive Number ◽  
Mobility Data ◽  
Nonpharmaceutical Interventions

Assessing the effects of early nonpharmaceutical interventions on coronavirus disease 2019 (COVID-19) spread is crucial for understanding and planning future control measures to combat the pandemic. We use observations of reported infections and deaths, human mobility data, and a metapopulation transmission model to quantify changes in disease transmission rates in U.S. counties from 15 March to 3 May 2020. We find that marked, asynchronous reductions of the basic reproductive number occurred throughout the United States in association with social distancing and other control measures. Counterfactual simulations indicate that, had these same measures been implemented 1 to 2 weeks earlier, substantial cases and deaths could have been averted and that delayed responses to future increased incidence will facilitate a stronger rebound of infections and death. Our findings underscore the importance of early intervention and aggressive control in combatting the COVID-19 pandemic.

Stability, Bifurcation and Optimal Control Analysis of a Malaria Model in a Periodic Environment

2018 ◽  
Vol 19 (6) ◽  
pp. 627-642 ◽  
Author(s):  
Prabir Panja ◽  
Shyamal Kumar Mondal ◽  
Joydev Chattopadhyay
Keyword(s):  
Optimal Control ◽  
Disease Transmission ◽  
Existence Condition ◽  
Infected Mosquito ◽  
Transmission Model ◽  
Control Analysis ◽  
Periodic Environment ◽  
Vector Population ◽  
Autonomous Case ◽  
Disease Transmission Model

AbstractIn this paper, a malaria disease transmission model has been developed. Here, the disease transmission rates from mosquito to human as well as human to mosquito and death rate of infected mosquito have been constituted by two variabilities: one is periodicity with respect to time and another is based on some control parameters. Also, total vector population is divided into two subpopulations such as susceptible mosquito and infected mosquito as well as the total human population is divided into three subpopulations such as susceptible human, infected human and recovered human. The biologically feasible equilibria and their stability properties have been discussed. Again, the existence condition of the disease has been illustrated theoretically and numerically. Hopf-bifurcation analysis has been done numerically for autonomous case of our proposed model with respect to some important parameters. At last, a optimal control problem is formulated and solved using Pontryagin’s principle. In numerical simulations, different possible combination of controls have been illustrated including the comparisons of their effectiveness.

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