scholarly journals Estimating local outbreak risks and the effects of non-pharmaceutical interventions in age-structured populations: SARS-CoV-2 as a case study

2021 ◽  
pp. 110983
Author(s):  
Francesca A. Lovell-Read ◽  
Silvia Shen ◽  
Robin N. Thompson
Keyword(s):  
Structured Populations ◽  
Age Structured ◽  
Pharmaceutical Interventions

scholarly journals Estimating local outbreak risks and the effects of non-pharmaceutical interventions in age-structured populations: SARS-CoV-2 as a case study

2021 ◽  
Author(s):  
Francesca A. Lovell-Read ◽  
Silvia Shen ◽  
Robin N. Thompson
Keyword(s):  
Process Model ◽  
Host Population ◽  
Structured Populations ◽  
School Closures ◽  
Related Factors ◽  
Social Distancing ◽  
Modelling Framework ◽  
Age Related ◽  
Pharmaceutical Interventions

AbstractDuring the COVID-19 pandemic, non-pharmaceutical interventions (NPIs) including school closures, workplace closures and social distancing policies have been employed worldwide to reduce transmission and prevent local outbreaks. However, transmission and the effectiveness of NPIs depend strongly on age-related factors including heterogeneities in contact patterns and pathophysiology. Here, using SARS-CoV-2 as a case study, we develop a branching process model for assessing the risk that an infectious case arriving in a new location will initiate a local outbreak, accounting for the age-stratification of the host population. We show that the risk of a local outbreak depends on the age of the index case, and we explore the effects of NPIs targeting individuals of different ages. Social distancing policies that reduce contacts outside of schools and workplaces and target individuals of all ages are predicted to reduce local outbreak risks substantially, whereas school closures have a more limited impact. When different NPIs are used in combination, the risk of local outbreaks can be eliminated. We also show that heightened surveillance of infectious individuals reduces the level of NPIs required to prevent local outbreaks, particularly if enhanced surveillance of symptomatic cases is combined with efforts to find and isolate nonsymptomatic infected individuals. Our results reflect real-world experience of the COVID-19 pandemic, during which combinations of intense NPIs have reduced transmission and the risk of local outbreaks. The general modelling framework that we present can be used to estimate local outbreak risks during future epidemics of a range of pathogens, accounting fully for age-related factors.

scholarly journals Life history changes and fisheries assessment performance: a case study for small yellow croaker

2019 ◽  
Vol 77 (2) ◽  
pp. 645-654
Author(s):  
Qi Lee ◽  
Alice Lee ◽  
Zunlei Liu ◽  
Cody S Szuwalski
Keyword(s):  
Life History ◽  
Reference Points ◽  
Structured Populations ◽  
Production Model ◽  
Life History Variation ◽  
Structured Model ◽  
Small Yellow Croaker ◽  
Age Structured ◽  
Age Structured Model

Abstract Many intensely exploited fish stocks have experienced changes in trophic structure and environmental conditions, resulting in non-stationary population processes. We evaluate the ability of assessment methods to estimate quantities used in management (like target biomasses and fishing mortalities) when life history processes are non-stationary and comprehensive data are not available. We use the small yellow croaker (Larimichthys polyactis) fishery in the East China and Yellow Seas as a case study. We simulate age-structured populations with time-varying fishery and life history characteristics similar to that of the small yellow croaker in China based on historical studies that demonstrate changes in life history. We then fit surplus production and statistical catch-at-age models to simulated catch and index data from these populations. Given our assumptions, both estimation models yielded biased quantities important to management. The production model estimated reference points associated with target biomass with less bias than the age-structured model, while the latter outperformed the former when estimating reference points associated with target fishing mortality. The age-structured model also better captured relative population trends and provided flexibility to consider impacts of life history changes over time. We suggest that assessments of similar stocks consider the potential of life history variation impact management quantities.

scholarly journals Frequency responses of age-structured populations: Pacific salmon as an example

2010 ◽  
Vol 78 (4) ◽  
pp. 239-249 ◽  
Author(s):  
Lee Worden ◽  
Louis W. Botsford ◽  
Alan Hastings ◽  
Matthew D. Holland
Keyword(s):  
Pacific Salmon ◽  
Structured Populations ◽  
Frequency Responses ◽  
Age Structured

The Role of Population Mobility and Non-Pharmaceutical Interventions on COVID-19 Infection: A Canadian Case Study of Granger-Causal Relationships

2021 ◽  
Author(s):  
Myrtha E. Reyna ◽  
Boxi Lin ◽  
Lehang Zhong ◽  
Michael Jongho Moon ◽  
Mohammad Kaviul Anam Khan ◽  
...  
Keyword(s):  
Causal Relationships ◽  
Population Mobility ◽  
Pharmaceutical Interventions

scholarly journals The effect of life-history and mode of inheritance on neutral genetic variability

2001 ◽  
Vol 77 (2) ◽  
pp. 153-166 ◽  
Author(s):  
BRIAN CHARLESWORTH
Keyword(s):  
Sequence Variation ◽  
Adult Mortality ◽  
Structured Populations ◽  
Human Populations ◽  
Effective Population ◽  
Transmission Modes ◽  
Population Sizes ◽  
Age Structured ◽  
Infinite Sites Model ◽  
Site Diversity

Formulae for the effective population sizes of autosomal, X-linked, Y-linked and maternally transmitted loci in age-structured populations are developed. The approximations used here predict both asymptotic rates of increase in probabilities of identity, and equilibrium levels of neutral nucleotide site diversity under the infinite-sites model. The applications of the results to the interpretation of data on DNA sequence variation in Drosophila, plant, and human populations are discussed. It is concluded that sex differences in demographic parameters such as adult mortality rates generally have small effects on the relative effective population sizes of loci with different modes of inheritance, whereas differences between the sexes in variance in reproductive success can have major effects, either increasing or reducing the effective population size for X-linked loci relative to autosomal or Y-linked loci. These effects need to be accounted for when trying to understand data on patterns of sequence variation for genes with different transmission modes.

Evolution in Age-Structured Populations.

1995 ◽  
Vol 83 (3) ◽  
pp. 548
Author(s):  
Tom J. de Jong ◽  
B. Charlesworth
Keyword(s):  
Structured Populations ◽  
Age Structured

scholarly journals Towards a better understanding of the dynamics of Aphis spiraecola Patch (Homoptera: Aphididae) populations in commercial alpine yarrow fields

2010 ◽  
Vol 42 (2) ◽  
pp. 103 ◽  
Author(s):  
Zulfaidah Penata Gama ◽  
Pablo Morlacchi ◽  
Giuseppe Carlo Lozzia ◽  
Johann Baumgärtner ◽  
Anna Giorgi
Keyword(s):  
Natural Enemy ◽  
Distributed Delay ◽  
Structured Populations ◽  
Temperature Dependent ◽  
Optimum Sample Size ◽  
Aphis Spiraecola ◽  
Different Temperatures ◽  
Mechanistic Basis ◽  
Age Structured ◽  
Optimum Sample

The spatial distribution of Aphis spiraecola Patch was studied in two commercial yarrow fields located in the Swiss and Italian Alps and represented by Taylor’s (1961) power law. The respective parameters indicate a highly aggregated distribution and lead to a high optimum sample size of 400-500 plants in the design of a sampling program. Opportunities for reducing the sampling efforts are discussed. The infestation patterns were studied on the basis of Vansickle’s (1977) time varying distributed delay adequate for modelling the dynamics of age-structured populations. Published literature data were used to parametrize the functions representing the temperature-dependent duration and survival of the nymphal and adult stage. Likewise, literature data were available to obtain reliable estimates for the parameters of the fecundity function comprising the reproductive profile and the number of nymphs produced at different temperatures. The field data were used to parametrize the functions for wing formation and a compound mortality compromising the effects of plant senescence, stem cutting and natural enemies. The model satisfactorily represented the observed infestation patterns. However, there are opportunities for improving parameter estimation and validation. Moreover, the separation of the compound mortality into host plant and natural enemy effects would improve the mechanistic basis of the model and lead towards a tool that could be used to study bottom-up and top-down effects in the yarrow-aphid-natural enemy system.

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