scholarly journals A stochastic contact network model for assessing outbreak risk of COVID-19 in workplaces

PLoS ONE ◽  
2022 ◽  
Vol 17 (1) ◽  
pp. e0262316
Author(s):  
Xi Guo ◽  
Abhineet Gupta ◽  
Anand Sampat ◽  
Chengwei Zhai
Keyword(s):  
Network Model ◽  
Cumulative Incidence ◽  
First Generation ◽  
Random Variable ◽  
Source Model ◽  
Control Measures ◽  
Contact Network ◽  
Risk Modeling ◽  
Bernoulli Random Variable ◽  
Model Code

The COVID-19 pandemic has drastically shifted the way people work. While many businesses can operate remotely, a large number of jobs can only be performed on-site. Moreover as businesses create plans for bringing workers back on-site, they are in need of tools to assess the risk of COVID-19 for their employees in the workplaces. This study aims to fill the gap in risk modeling of COVID-19 outbreaks in facilities like offices and warehouses. We propose a simulation-based stochastic contact network model to assess the cumulative incidence in workplaces. First-generation cases are introduced as a Bernoulli random variable using the local daily new case rate as the success rate. Contact networks are established through randomly sampled daily contacts for each of the first-generation cases and successful transmissions are established based on a randomized secondary attack rate (SAR). Modification factors are provided for SAR based on changes in airflow, speaking volume, and speaking activity within a facility. Control measures such as mask wearing are incorporated through modifications in SAR. We validated the model by comparing the distribution of cumulative incidence in model simulations against real-world outbreaks in workplaces and nursing homes. The comparisons support the model’s validity for estimating cumulative incidences for short forecasting periods of up to 15 days. We believe that the current study presents an effective tool for providing short-term forecasts of COVID-19 cases for workplaces and for quantifying the effectiveness of various control measures. The open source model code is made available at github.com/abhineetgupta/covid-workplace-risk.

scholarly journals Field Efficacy of Steinernema sp. (Rhabditida: Steinernematidae) on the Colorado Potato Beetle Overwintering Generation

Plants ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1464
Author(s):  
Maja Čačija ◽  
Renata Bažok ◽  
Majda Kolenc ◽  
Tena Bujas ◽  
Zrinka Drmić ◽  
...  
Keyword(s):  
Colorado Potato Beetle ◽  
First Generation ◽  
Control Measures ◽  
Recommended Dose ◽  
Steinernema Feltiae ◽  
First Year ◽  
Potato Beetle ◽  
Field Efficacy ◽  
Second Year ◽  
Economic Pest

Colorado potato beetle (CPB) is an economic pest of potato that has developed resistance to all classes of chemical insecticides, thus requiring alternative control measures. As a potential solution, entomopathogenic nematodes (EPNs) have proven effective in suppressing this pest, but their efficacy against overwintering generations of CPB in Croatia has not been sufficiently researched. The aim of this two-year (2018–2019) field study was to determine the efficacy of Steinernema feltiae and Steinernema carpocapsae applied to overwintering CPB adults. EPNs were applied at three doses (7.5 mil./10 m2, 5.0 mil./10 m2 (the recommended dose) and 2.5 mil./10 m2) by watering the soil where the adults were overwintering. The first-year results were satisfactory for both EPNs: the efficacy of S. feltiae ranged from 79.03% to 100.00%, while the efficacy of S. carpocapsae ranged from 77.32% to 96.22%. In the second year, the highest efficacy (69.57%) was obtained using the recommended dose of S. feltiae. Although the results are not consistent across the two years of our study and suggest further research, they indicate that EPNs have great potential in controlling overwintering CPB generations to reduce first generation abundance and damage, and also to prevent the spread of new generations to surrounding potato growing areas.

scholarly journals Modifying the network-based stochastic SEIR model to account for quarantine: an application to COVID-19

2021 ◽  
Vol 10 (s1) ◽  
Author(s):  
Chris Groendyke ◽  
Adam Combs
Keyword(s):  
Network Model ◽  
Transmission Rate ◽  
Disease Spread ◽  
Contact Network ◽  
Model Parameters ◽  
Seir Model ◽  
Disease States ◽  
Potential Contact ◽  
The Mean ◽  
Infectious State

Abstract Objectives: Diseases such as SARS-CoV-2 have novel features that require modifications to the standard network-based stochastic SEIR model. In particular, we introduce modifications to this model to account for the potential changes in behavior patterns of individuals upon becoming symptomatic, as well as the tendency of a substantial proportion of those infected to remain asymptomatic. Methods: Using a generic network model where every potential contact exists with the same common probability, we conduct a simulation study in which we vary four key model parameters (transmission rate, probability of remaining asymptomatic, and the mean lengths of time spent in the exposed and infectious disease states) and examine the resulting impacts on various metrics of epidemic severity, including the effective reproduction number. We then consider the effects of a more complex network model. Results: We find that the mean length of time spent in the infectious state and the transmission rate are the most important model parameters, while the mean length of time spent in the exposed state and the probability of remaining asymptomatic are less important. We also find that the network structure has a significant impact on the dynamics of the disease spread. Conclusions: In this article, we present a modification to the network-based stochastic SEIR epidemic model which allows for modifications to the underlying contact network to account for the effects of quarantine. We also discuss the changes needed to the model to incorporate situations where some proportion of the individuals who are infected remain asymptomatic throughout the course of the disease.

A new robust Kalman filter with measurement loss based on mixing distribution

2021 ◽  
pp. 014233122110549
Author(s):  
Chenghao Shan ◽  
Weidong Zhou ◽  
Yefeng Yang ◽  
Hanyu Shan
Keyword(s):  
Kalman Filter ◽  
Likelihood Function ◽  
State Space Model ◽  
Random Variable ◽  
Superior Performance ◽  
Gaussian State ◽  
Bernoulli Random Variable ◽  
Mixing Distribution ◽  
Robust Kalman Filter ◽  
Heavy Tailed

A new robust Kalman filter (KF) based on mixing distribution is presented to address the filtering issue for a linear system with measurement loss (ML) and heavy-tailed measurement noise (HTMN) in this paper. A new Student’s t-inverse-Wishart-Gamma mixing distribution is derived to more rationally model the HTMN. By employing a discrete Bernoulli random variable (DBRV), the form of measurement likelihood function of double mixing distributions is converted from a weighted sum to an exponential product, and a hierarchical Gaussian state-space model (HGSSM) is therefore established. Finally, the system state, the intermediate random variables (IRVs) of the new STIWG distribution, and the DBRV are simultaneously estimated by utilizing the variational Bayesian (VB) method. Numerical example simulation experiment indicates that the proposed filter in this paper has superior performance than current algorithms in processing ML and HTMN.

scholarly journals Risk Modeling of Bat Rabies in the Caribbean Islands

2020 ◽  
Vol 5 (1) ◽  
pp. 35
Author(s):  
Clint N. Morgan ◽  
Ryan M. Wallace ◽  
Alexandra Vokaty ◽  
Janine F.R. Seetahal ◽  
Yoshinori J. Nakazawa
Keyword(s):  
Pairwise Comparison ◽  
Control Measures ◽  
Risk Modeling ◽  
Cayman Islands ◽  
The Bahamas ◽  
Analytic Hierarchy ◽  
Caribbean Islands ◽  
Control And Prevention ◽  
The Caribbean ◽  
Bat Rabies

Rabies surveillance and control measures vary significantly between Caribbean islands. The Centers for Disease Control and Prevention currently recommends certain groups of U.S. travelers to any Caribbean island receive pre-exposure rabies immunization. However, most islands self-declare as “rabies free”, and have never publicly released data to support rabies-free claims. We used the Analytic Hierarchy Process to create pairwise comparison values among five risk factors determined by subject matter experts. Risk factor weights were calculated and used in a geospatial analysis to calculate a risk value for each island nation (higher values indicate higher risk). Risk values ranged from 8.73 (Trinidad) to 1.57 (The Bahamas, Turks and Caicos Islands). All four countries that have documented occurrences of laboratory confirmed rabid bats were ranked highest (Trinidad and Tobago, Grenada, Cuba, Dominican Republic), as well as Haiti. The top five highest risk countries that currently have no reports of bat rabies include St. Vincent and the Grenadines, Jamaica, Puerto Rico, the Cayman Islands, and Dominica. This study reviews the inter-island movement potential of bats, designates areas of high risk for bat-associated rabies within the Caribbean islands, and demonstrates a need for further surveillance efforts in bat populations within islands that self-declare as rabies free.

Seasonal Occurrence of Pieris rapae (L.) (Lepidoptera: Pieridae) in Southwest Virginia

1995 ◽  
Vol 30 (2) ◽  
pp. 262-272 ◽  
Author(s):  
David N. Gaines ◽  
L. T. Kok
Keyword(s):  
Count Data ◽  
First Generation ◽  
Pieris Rapae ◽  
Growth Period ◽  
Control Measures ◽  
Seasonal Occurrence ◽  
Fifth Generation ◽  
Sixth Generation ◽  
Field Plots ◽  
Eggs And Larvae

In Virginia, Pieris rapae (L.) phenology is not well established because earlier studies focused on its occurrence within the growth period of a particular crop. In this study, conducted in 1989 and 1990, we sampled multiple crops in both spring and fall plantings and these data were compared with those from earlier studies to obtain an overall pattern of seasonal occurrence. In 1989, spring crops of broccoli, cabbage, and kale were planted in field plots in Montgomery Co., VA, and sampled weekly for the eggs and larvae of P. rapae. In 1990, both spring and fall crops were planted and sampled. Four P. rapae generations (egg count peaks) were observed in 1989 and 1990, but comparison of data from both years suggested a fifth generation was possible in this region. When these data are compared with egg count data from seven previous years (1981–1988; 1985 not included), evidence indicates a first generation in mid-May, and consistent second and third generations in mid-June and mid-July, respectively. The June and July generations were always well defined by high egg and larva counts per plant. Less predictable are the fourth and fifth generations which may both occur in August or one generation each in August and September. When fourth and fifth generations occur in early and late August, a sixth generation may occur in late September. The regular occurrence and size of the second and third generation can facilitate the planning and implementation of biological or other control measures for P. rapae in this region.

Probabilistic network modelling of the impact of penicillin consumption on spread of pneumococci

2010 ◽  
Vol 139 (9) ◽  
pp. 1351-1360 ◽  
Author(s):  
D. KARLSSON
Keyword(s):  
Population Dynamics ◽  
Network Model ◽  
Age Distribution ◽  
Clinical Problem ◽  
Control Measures ◽  
Network Modelling ◽  
Model Simulations ◽  
Probabilistic Network ◽  
Strain Competition ◽  
The Impact

SUMMARYThe worldwide increase of resistant S. pneumoniae is a growing clinical problem. In several countries, a more restrictive use of penicillin has been promoted in hope of slowing the rates of resistant pneumococci. However, the consequences of such an action on pneumococcal population dynamics are not fully understood. Thus, a network model was constructed to assess the impacts of penicillin consumption and between-strain competition on the spread of penicillin non-susceptible pneumococci. Model simulations suggest that the age distribution for carriage of penicillin non-susceptible pneumococci, in contrast to susceptible pneumococci, is affected by penicillin consumption. Furthermore, it appears extremely difficult to reduce the incidence of penicillin non-susceptible pneumococci by simply controlling penicillin consumption, assuming that reduced penicillin susceptibility does not confer a fitness cost for the organism. A more judicious use of penicillin together with control measures are in that case required to manage penicillin resistance in pneumococci.

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