scholarly journals Understanding the Importance of Contact Heterogeneity and Variable Infectiousness in the Dynamics of a Large Norovirus Outbreak

2019 ◽  
Vol 70 (3) ◽  
pp. 493-500 ◽  
Author(s):  
Jon Zelner ◽  
Carly Adams ◽  
Joshua Havumaki ◽  
Ben Lopman
Keyword(s):  
Transmission Rate ◽  
Transmission Dynamics ◽  
Dynamics Modeling ◽  
Outbreak Response ◽  
Final Size ◽  
Modeling Tools ◽  
Bayesian Hierarchical ◽  
Contact Patterns ◽  
Lower Transmission ◽  
And Control

Abstract Background Large norovirus (NoV) outbreaks are explosive in nature and vary widely in final size and duration, suggesting that superspreading combined with heterogeneous contact may explain these dynamics. Modeling tools that can capture heterogeneity in infectiousness and contact are important for NoV outbreak prevention and control, yet they remain limited. Methods Data from a large NoV outbreak at a Dutch scout jamboree, which resulted in illness among 326 (of 4500 total) individuals from 7 separate camps, were used to examine the contributions of individual variation in infectiousness and clustered contact patterns to the transmission dynamics. A Bayesian hierarchical model of heterogeneous, clustered outbreak transmission was applied to represent (1) between-individual heterogeneity in infectiousness and (2) heterogeneous patterns of contact. Results We found wide heterogeneity in infectiousness across individuals, suggestive of superspreading. Nearly 50% of individual infectiousness was concentrated in the individual’s subcamp of residence, with the remainder distributed over other subcamps. This suggests a source-and-sink dynamic in which subcamps with greater average infectiousness fed cases to those with a lower transmission rate. Although the per capita transmission rate within camps was significantly greater than that between camps, the large pool of susceptible individuals across camps enabled similar numbers of secondary cases generated between versus within camps. Conclusions The consideration of clustered transmission and heterogeneous infectiousness is important for understanding NoV transmission dynamics. Models including these mechanisms may be useful for providing early warning and guiding outbreak response.

scholarly journals On the study of full transmission dynamics of COVID-19 in Wuhan

2020 ◽  
Author(s):  
Chong You ◽  
Xin Gai ◽  
Yuan Zhang ◽  
Xiao-Hua Zhou
Keyword(s):  
Transmission Rate ◽  
Control Measure ◽  
Transmission Mechanism ◽  
Control Measures ◽  
Transmission Dynamics ◽  
Modified Model ◽  
Pcr Screening ◽  
Active Virus ◽  
Current Outbreak ◽  
And Control

Abstract The current outbreak of coronavirus disease 2019 (COVID-19) has quickly spread across countries and become a global crisis. Understanding the transmission mechanism and effects of interventions is critical to the prevention and control of the COVID-19 pandemic. A recent study by Hao et al (2020) provided an interesting perspective on the transmission dynamics of COVID-19 in Wuhan and inferred that 87% of the infections before 8 March 2020 were not laboratory-confirmed. However we believe that there are a few major issues due to the vagueness in the definitions of compartments and inconsistence in the settings of parameters. In this paper, we clarify the definitions of the model compartments and raise questions in regard to the underlying homogenous assumption within compartments and settings of the parameters in the dynamic model by Hao et al (2020), and furthermore offer a modified model to resolve these potential limitations. Compared with the model in Hao et al (2020), the active virus carriers were predicted to persist for a longer period in our model which is well consistent with the active virus carriers detected in Wuhan in mid-May. Our model suggests that control measures cannot be easily lifted while continuous efforts are needed to contain the spread of the pandemic; a universal PT-PCR screening is essential to detect hidden cases before lifting control measure. In addition, we also provide a possible solution to solve the problem of heterogeneity transmission rate in disease courses.

scholarly journals Establishment and lineage dynamics of the SARS-CoV-2 epidemic in the UK

Science ◽  
2021 ◽  
pp. eabf2946
Author(s):  
Louis du Plessis ◽  
John T. McCrone ◽  
Alexander E. Zarebski ◽  
Verity Hill ◽  
Christopher Ruis ◽  
...  
Keyword(s):  
Large Scale ◽  
Phylogenetic Analyses ◽  
Transmission Dynamics ◽  
Genetic Lineage ◽  
Size Dependent ◽  
Spatio Temporal ◽  
The Uk ◽  
Lineage Structure ◽  
And Control ◽  
Lineage Diversity

The UK’s COVID-19 epidemic during early 2020 was one of world’s largest and unusually well represented by virus genomic sampling. Here we reveal the fine-scale genetic lineage structure of this epidemic through analysis of 50,887 SARS-CoV-2 genomes, including 26,181 from the UK sampled throughout the country’s first wave of infection. Using large-scale phylogenetic analyses, combined with epidemiological and travel data, we quantify the size, spatio-temporal origins and persistence of genetically-distinct UK transmission lineages. Rapid fluctuations in virus importation rates resulted in >1000 lineages; those introduced prior to national lockdown tended to be larger and more dispersed. Lineage importation and regional lineage diversity declined after lockdown, while lineage elimination was size-dependent. We discuss the implications of our genetic perspective on transmission dynamics for COVID-19 epidemiology and control.

scholarly journals The effects of flooding and weather conditions on leptospirosis transmission in Thailand

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sudarat Chadsuthi ◽  
Karine Chalvet-Monfray ◽  
Anuwat Wiratsudakul ◽  
Charin Modchang
Keyword(s):  
Sensitivity Analysis ◽  
Public Education ◽  
Mathematical Models ◽  
Disease Transmission ◽  
Transmission Rate ◽  
Weather Conditions ◽  
Transmission Dynamics ◽  
Multiplication Rate ◽  
High Degree ◽  
Transmission Models

AbstractThe epidemic of leptospirosis in humans occurs annually in Thailand. In this study, we have developed mathematical models to investigate transmission dynamics between humans, animals, and a contaminated environment. We compared different leptospire transmission models involving flooding and weather conditions, shedding and multiplication rate in a contaminated environment. We found that the model in which the transmission rate depends on both flooding and temperature, best-fits the reported human data on leptospirosis in Thailand. Our results indicate that flooding strongly contributes to disease transmission, where a high degree of flooding leads to a higher number of infected individuals. Sensitivity analysis showed that the transmission rate of leptospires from a contaminated environment was the most important parameter for the total number of human cases. Our results suggest that public education should target people who work in contaminated environments to prevent Leptospira infections.

scholarly journals Control/Network Codesign Basics for IP-Based Shared Networks

2011 ◽  
Vol 2011 ◽  
pp. 1-23 ◽  
Author(s):  
Miguel Díaz-Cacho Medina ◽  
Emma Delgado Romero ◽  
Antonio Barreiro Blas
Keyword(s):  
Control Systems ◽  
Networked Control Systems ◽  
Transmission Rate ◽  
Design Parameters ◽  
Control Network ◽  
Transport Protocol ◽  
Test Platform ◽  
Shared Networks ◽  
The Stability ◽  
And Control

Network and control relationship is an essential aspect in the design of networked control systems (NCSs). The design parameters are mainly centered in the transmission rate and in the packet structure, and some studies have been made to determine how transmission rate affects the network delay and consequently the stability of the control. In Internet, these analysis are mathematically complex due to the large number of different potential scenarios. Using empirical methods, this work deduces that the transmission scheduling problem of an NCS can be solved by designing an appropriate transport protocol, taken into account high and periodic sampling rates. The transport protocol features are determined by simulation, using a new test platform based on the NS2 network simulation suite, to develop control/network codesign solutions. Conclusions of this paper are that the transport features are packet-loss-based flow control, best effort, and fairness, supplemented by a packet priority scheme.

scholarly journals Early transmission dynamics of SARS-CoV-2 in Indonesia

2021 ◽  
Vol 1 (1) ◽  
pp. 1-6
Author(s):  
Mudatsir Mudatsir ◽  
Synat Keam ◽  
Wira Winardi ◽  
Amanda Yufika ◽  
Ali A. Rabaan ◽  
...  
Keyword(s):  
Surveillance System ◽  
Disease Surveillance ◽  
Capital City ◽  
Transmission Dynamics ◽  
Disease Surveillance System ◽  
First Case ◽  
Directorate General ◽  
The Government ◽  
And Control ◽  
Importation Risk

The objective of this study was to determine the transmission dynamics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and to evaluate the vigilance of the health system during the early phase of coronavirus disease 2019 (COVID-19) outbreak in Indonesia. The early epidemiology and transmission chains of COVID-19 were analyzed based on data from the Directorate General of Disease Prevention and Control of the Indonesian Ministry of Health. The results of this study shown although Indonesia is a country with a high relative importation risk of SARS-CoV-2, the first two cases of COVID-19 were identified on March 2, 2020. This relatively late date by regional standards raises the possibility of undetected cases beforehand. The first case was a foreigner citizen who visited the capital city of Jakarta and later was diagnosed COVID-19 after returning from Indonesia. One week later after the first case, 27 confirmed COVID-19 cases had been reported in Indonesia, and the majority of the cases were clustered together. Apart from the possibility of underdetection of COVID-19 cases in the country, the government has strengthened the disease surveillance system and established an outbreak preparedness system to diagnose and control COVID-19. 

scholarly journals Effects of reward on oculomotor control

2016 ◽  
Vol 116 (5) ◽  
pp. 2453-2466 ◽  
Author(s):  
Brónagh McCoy ◽  
Jan Theeuwes
Keyword(s):  
Reward Magnitude ◽  
Saccade Latency ◽  
Oculomotor Control ◽  
Distractor Location ◽  
Landing Position ◽  
Bayesian Hierarchical ◽  
Visual Hemifield ◽  
High Reward ◽  
And Control ◽  
Remote Distractor Effect

The present study examines the extent to which distractors that signal the availability of monetary reward on a given trial affect eye movements. We used a novel eye movement task in which observers had to follow a target around the screen while ignoring distractors presented at varying locations. We examined the effects of reward magnitude and distractor location on a host of oculomotor properties, including saccade latency, amplitude, landing position, curvature, and erroneous saccades toward the distractor. We found consistent effects of reward magnitude on classic oculomotor phenomena such as the remote distractor effect, the global effect, and oculomotor capture by the distractor. We also show that a distractor in the visual hemifield opposite to the target had a larger effect on oculomotor control than an equidistant distractor in the same hemifield as the target. Bayesian hierarchical drift diffusion modeling revealed large differences in drift rate depending on the reward value, location, and visual hemifield of the distractor stimulus. Our findings suggest that high reward distractors not only capture the eyes but also affect a multitude of oculomotor properties associated with oculomotor inhibition and control.

scholarly journals Predicting the early depleting transmission dynamics of COVID-19: A time-varying SIR model

2020 ◽  
Author(s):  
Kian Boon Law ◽  
Kalaiarasu M Peariasamy ◽  
Balvinder Singh Gill ◽  
Sarbhan Singh Lakha Singh ◽  
Bala Murali Sundram ◽  
...  
Keyword(s):  
Temporal Trends ◽  
Model Fitting ◽  
Sir Model ◽  
Transmission Dynamics ◽  
Time Varying ◽  
Force Of Infection ◽  
Planning And Control ◽  
The Mean ◽  
And Control ◽  
Absolute Percent Error

Abstract The susceptible-infectious-removed (SIR) model offers the simplest framework to study transmission dynamics of COVID-19, however, it does not factor in its early depleting trend observed during a lockdown. We modified the SIR model to specifically simulate the early depleting transmission dynamics of COVID-19 to better predict its temporal trend in Malaysia. The classical SIR model was fitted to observed total (I total), active (I), and removed (R) cases of COVID-19 before lockdown to estimate the basic reproduction number. Next, the model was modified with a partial time-varying force of infection, given by a proportionally depleting transmission coefficient, βt, and a fractional term, z. The modified SIR model was then fitted to observed data over 6 weeks during the lockdown. Model fitting and projection were validated using the mean absolute percent error (MAPE). The transmission dynamics of COVID-19 was interrupted immediately by the lockdown. The modified SIR model projected the depleting temporal trends with lowest MAPE for I total, followed by I, I daily, and R. During lockdown, the dynamics of COVID-19 depleted at a rate of 4·7% each day with a decreased capacity of 40%. For 7–day and 14–day projections, the modified SIR model accurately predicted I total, I, and R. The depleting transmission dynamics for COVID-19 during lockdown can be accurately captured by time-varying SIR model. Projection generated based on observed data is useful for future planning and control of COVID-19.

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