scholarly journals The impact of long-term non-pharmaceutical interventions on COVID-19 epidemic dynamics and control: the value and limitations of early models

2021 ◽  
Vol 288 (1957) ◽  
pp. 20210811
Author(s):  
Marissa L. Childs ◽  
Morgan P. Kain ◽  
Mallory J. Harris ◽  
Devin Kirk ◽  
Lisa Couper ◽  
...  
Keyword(s):  
Reproduction Number ◽  
Compartment Model ◽  
Limited Information ◽  
Epidemic Dynamics ◽  
Transmission Parameters ◽  
Santa Clara County ◽  
Dynamics And Control ◽  
Intervention Policy ◽  
And Control ◽  
The Impact

Mathematical models of epidemics are important tools for predicting epidemic dynamics and evaluating interventions. Yet, because early models are built on limited information, it is unclear how long they will accurately capture epidemic dynamics. Using a stochastic SEIR model of COVID-19 fitted to reported deaths, we estimated transmission parameters at different time points during the first wave of the epidemic (March–June, 2020) in Santa Clara County, California. Although our estimated basic reproduction number ( R 0 ) remained stable from early April to late June (with an overall median of 3.76), our estimated effective reproduction number ( R E ) varied from 0.18 to 1.02 in April before stabilizing at 0.64 on 27 May. Between 22 April and 27 May, our model accurately predicted dynamics through June; however, the model did not predict rising summer cases after shelter-in-place orders were relaxed in June, which, in early July, was reflected in cases but not yet in deaths. While models are critical for informing intervention policy early in an epidemic, their performance will be limited as epidemic dynamics evolve. This paper is one of the first to evaluate the accuracy of an early epidemiological compartment model over time to understand the value and limitations of models during unfolding epidemics.

scholarly journals The impact of long-term non-pharmaceutical interventions on COVID-19 epidemic dynamics and control

2020 ◽  
Author(s):  
Marissa L. Childs ◽  
Morgan P. Kain ◽  
Devin Kirk ◽  
Mallory Harris ◽  
Lisa Couper ◽  
...  
Keyword(s):  
Social Distancing ◽  
Epidemic Dynamics ◽  
Start Date ◽  
Santa Clara County ◽  
Rigorous Testing ◽  
Life Saving ◽  
Dynamics And Control ◽  
And Control ◽  
The Impact ◽  
Pharmaceutical Interventions

AbstractNon-pharmaceutical interventions to combat COVID-19 transmission have worked to slow the spread of the epidemic but can have high socio-economic costs. It is critical we understand the efficacy of non-pharmaceutical interventions to choose a safe exit strategy. Many current models are not suitable for assessing exit strategies because they do not account for epidemic resurgence when social distancing ends prematurely (e.g., statistical curve fits) nor permit scenario exploration in specific locations.We developed an SEIR-type mechanistic epidemiological model of COVID-19 dynamics to explore temporally variable non-pharmaceutical interventions. We provide an interactive tool and code to estimate the transmission parameter, β, and the effective reproduction number, . We fit the model to Santa Clara County, California, where an early epidemic start date and early shelter-in-place orders could provide a model for other regions.As of April 22, 2020, we estimate an of 0.982 (95% CI: 0.849 - 1.107) in Santa Clara County. After June 1 (the end-date for Santa Clara County shelter-in-place as of April 27), we estimate a shift to partial social distancing, combined with rigorous testing and isolation of symptomatic individuals, is a viable alternative to indefinitely maintaining shelter-in-place. We also estimate that if Santa Clara County had waited one week longer before issuing shelter-in-place orders, 95 additional people would have died by April 22 (95% CI: 7 - 283).Given early life-saving shelter-in-place orders in Santa Clara County, longer-term moderate social distancing and testing and isolation of symptomatic individuals have the potential to contain the size and toll of the COVID-19 pandemic in Santa Clara County, and may be effective in other locations.

Heterogeneities in schistosome transmission dynamics and control

Parasitology ◽  
1998 ◽  
Vol 117 (5) ◽  
pp. 475-482 ◽  
Author(s):  
M. E. J. WOOLHOUSE ◽  
J.-F. ETARD ◽  
K. DIETZ ◽  
P. D. NDHLOVU ◽  
S. K. CHANDIWANA
Keyword(s):  
Reproduction Number ◽  
Transmission Dynamics ◽  
Water Contact ◽  
Contact Rates ◽  
Control Programmes ◽  
Contact Data ◽  
Dynamics And Control ◽  
And Control ◽  
The Impact ◽  
The Basic Reproduction Number

We review the theoretical framework for exploring the impact of individual and spatial heterogeneities in patterns of exposure and contamination and on the basic reproduction number, R0, for human schistosomes. Analysis of water contact data for 5 communities in Zimbabwe and Mali suggests that the impact is substantial, increasing R0 by factors of up to 6·5, mostly due to highly overdispersed distributions of contact rates among individuals. Several practical conclusions emerge: concentration of contacts at a single site should be avoided; the impact of control targeted at certain sites cannot be predicted without knowledge of how individuals' contacts are distributed among sites; control programmes targeted at individuals or sites contributing most to transmission can be very efficient but, conversely, will be ineffective if any of these individuals or sites are missed.

A multigroup model for cholera dynamics and control

2015 ◽  
Vol 09 (01) ◽  
pp. 1650001 ◽  
Author(s):  
Drew Posny ◽  
Chairat Modnak ◽  
Jin Wang
Keyword(s):  
Reproduction Number ◽  
Vaccination Strategy ◽  
Sharp Threshold ◽  
Indirect Transmission ◽  
Dynamics And Control ◽  
Simulation Results ◽  
Transmission Pathways ◽  
And Control ◽  
Control Study ◽  
The Basic Reproduction Number

We propose a general multigroup model for cholera dynamics that involves both direct and indirect transmission pathways and that incorporates spatial heterogeneity. Under biologically feasible conditions, we show that the basic reproduction number R0 remains a sharp threshold for cholera dynamics in multigroup settings. We verify the analysis by numerical simulation results. We also perform an optimal control study to explore optimal vaccination strategy for cholera outbreaks.

scholarly journals Dynamics and control of measles in Portugal: Accessing the impact of anticipating the age for the first dose of MMR from 15 to 12 months of age

Vaccine ◽  
2008 ◽  
Vol 26 (19) ◽  
pp. 2418-2427 ◽  
Author(s):  
Ana Cristina Paulo ◽  
Manuel C. Gomes ◽  
M.Gabriela M. Gomes
Keyword(s):  
Dynamics And Control ◽  
And Control ◽  
The Impact

scholarly journals Mathematical modelling and phylodynamics for the study of dog rabies dynamics and control: A scoping review

2021 ◽  
Vol 15 (5) ◽  
pp. e0009449
Author(s):  
Maylis Layan ◽  
Simon Dellicour ◽  
Guy Baele ◽  
Simon Cauchemez ◽  
Hervé Bourhy
Keyword(s):  
Mathematical Modelling ◽  
Mathematical Models ◽  
Scoping Review ◽  
Control Strategies ◽  
Domestic Dog ◽  
Interdisciplinary Approaches ◽  
Dynamics And Control ◽  
And Control ◽  
The Impact

Background Rabies is a fatal yet vaccine-preventable disease. In the last two decades, domestic dog populations have been shown to constitute the predominant reservoir of rabies in developing countries, causing 99% of human rabies cases. Despite substantial control efforts, dog rabies is still widely endemic and is spreading across previously rabies-free areas. Developing a detailed understanding of dog rabies dynamics and the impact of vaccination is essential to optimize existing control strategies and developing new ones. In this scoping review, we aimed at disentangling the respective contributions of mathematical models and phylodynamic approaches to advancing the understanding of rabies dynamics and control in domestic dog populations. We also addressed the methodological limitations of both approaches and the remaining issues related to studying rabies spread and how this could be applied to rabies control. Methodology/principal findings We reviewed how mathematical modelling of disease dynamics and phylodynamics have been developed and used to characterize dog rabies dynamics and control. Through a detailed search of the PubMed, Web of Science, and Scopus databases, we identified a total of n = 59 relevant studies using mathematical models (n = 30), phylodynamic inference (n = 22) and interdisciplinary approaches (n = 7). We found that despite often relying on scarce rabies epidemiological data, mathematical models investigated multiple aspects of rabies dynamics and control. These models confirmed the overwhelming efficacy of massive dog vaccination campaigns in all settings and unraveled the role of dog population structure and frequent introductions in dog rabies maintenance. Phylodynamic approaches successfully disentangled the evolutionary and environmental determinants of rabies dispersal and consistently reported support for the role of reintroduction events and human-mediated transportation over long distances in the maintenance of rabies in endemic areas. Potential biases in data collection still need to be properly accounted for in most of these analyses. Finally, interdisciplinary studies were determined to provide the most comprehensive assessments through hypothesis generation and testing. They also represent new avenues, especially concerning the reconstruction of local transmission chains or clusters through data integration. Conclusions/significance Despite advances in rabies knowledge, substantial uncertainty remains regarding the mechanisms of local spread, the role of wildlife in dog rabies maintenance, and the impact of community behavior on the efficacy of control strategies including vaccination of dogs. Future integrative approaches that use phylodynamic analyses and mechanistic models within a single framework could take full advantage of not only viral sequences but also additional epidemiological information as well as dog ecology data to refine our understanding of rabies spread and control. This would represent a significant improvement on past studies and a promising opportunity for canine rabies research in the frame of the One Health concept that aims to achieve better public health outcomes through cross-sector collaboration.

scholarly journals Transmission dynamics and control of multidrug-resistant Klebsiella pneumoniae in neonates in a developing country

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Thomas Crellen ◽  
Paul Turner ◽  
Sreymom Pol ◽  
Stephen Baker ◽  
To Nguyen Thi Nguyen ◽  
...  
Keyword(s):  
Klebsiella Pneumoniae ◽  
Neonatal Intensive Care ◽  
Dynamic Models ◽  
Generation Cephalosporin ◽  
Multidrug Resistant ◽  
Transmission Risk ◽  
Dynamics And Control ◽  
One Year ◽  
And Control ◽  
The Impact

Multidrug-resistant Klebsiella pneumoniae is an increasing cause of infant mortality in developing countries. We aimed to develop a quantitative understanding of the drivers of this epidemic by estimating the effects of antibiotics on nosocomial transmission risk, comparing competing hypotheses about mechanisms of spread, and quantifying the impact of potential interventions. Using a sequence of dynamic models, we analysed data from a one-year prospective carriage study in a Cambodian neonatal intensive care unit with hyperendemic third-generation cephalosporin-resistant K. pneumoniae. All widely-used antibiotics except imipenem were associated with an increased daily acquisition risk, with an odds ratio for the most common combination (ampicillin + gentamicin) of 1.96 (95% CrI 1.18, 3.36). Models incorporating genomic data found that colonisation pressure was associated with a higher transmission risk, indicated sequence type heterogeneity in transmissibility, and showed that within-ward transmission was insufficient to maintain endemicity. Simulations indicated that increasing the nurse-patient ratio could be an effective intervention.

scholarly journals Transmission dynamics and control measures of COVID-19 outbreak in China: a modelling study

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Xu-Sheng Zhang ◽  
Emilia Vynnycky ◽  
Andre Charlett ◽  
Daniela De Angelis ◽  
Zhengji Chen ◽  
...  
Keyword(s):  
Reproduction Number ◽  
Early Stage ◽  
Case Fatality ◽  
Control Measures ◽  
Infected People ◽  
Contact Rates ◽  
Multiple Datasets ◽  
Dynamics And Control ◽  
Successful Control ◽  
And Control

AbstractCOVID-19 is reported to have been brought under control in China. To understand the COVID-19 outbreak in China and provide potential lessons for other parts of the world, in this study we apply a mathematical model with multiple datasets to estimate the transmissibility of the SARS-CoV-2 virus and the severity of the illness associated with the infection, and how both were affected by unprecedented control measures. Our analyses show that before 19th January 2020, 3.5% (95% CI 1.7–8.3%) of  infected people were detected; this percentage increased to 36.6% (95% CI 26.1–55.4%) thereafter. The basic reproduction number (R0) was 2.33 (95% CI 1.96–3.69) before 8th February 2020; then the effective reproduction number dropped to 0.04(95% CI 0.01–0.10). This estimation also indicates that control measures taken since 23rd January 2020 affected the transmissibility about 2 weeks after they were introduced. The confirmed case fatality rate is estimated at 9.6% (95% CI 8.1–11.4%) before 15 February 2020, and then it reduced to 0.7% (95% CI 0.4–1.0%). This shows that SARS-CoV-2 virus is highly transmissible but may be less severe than SARS-CoV-1 and MERS-CoV. We found that at the early stage, the majority of R0 comes from undetected infectious people. This implies that successful control in China was achieved through reducing the contact rates among people in the general population and increasing the rate of detection and quarantine of the infectious cases.

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