scholarly journals Quantitative modeling and analysis show country-specific optimization of quarantine measures can potentially circumvent COVID19 infection spread post lockdown

2020 ◽  
Author(s):  
Uddipan Sarma ◽  
Bhaswar Ghosh
Keyword(s):  
Reproduction Number ◽  
Transmission Rate ◽  
Fold Increase ◽  
Modeling And Analysis ◽  
Infection Dynamics ◽  
The Usa ◽  
Data Driven Modeling ◽  
Second Wave ◽  
Country Specific ◽  
Infection Spread

AbstractThe COVID19 outbreak, which started in Wuhan, is now spread across 200+ countries with over 6 million reported infections and a death toll over 350 thousand. In response, and primarily in the absence of a vaccine, many countries have implemented lockdown to ensure social distancing and started rigorously quarantining the infected subjects. In this study, we attempt to identify the most potent component(s) in the system that can be manipulated via human intervention. Firstly, analysis of the metadata for 93 countries showed a reduction in the estimated reproduction number (a month post-infection) is correlated to the testing rate in a country. To systematically study the dynamics of infection we next built epidemic models for 23 different countries and calibrated the confirmed, recovered, and dead population trajectories in the model to the respective data from WHO. The countries chosen either had the infection peak long crossed; peak recently reached but still with significant daily infection, or, infection peak is yet to arrive. Our model successfully fits data from all 23 countries and provides us with incubation time, transmission rate, quarantine, recovery, and death rates for each country. With further analysis, we found infection spread towards a much larger second wave can be controlled via a rigorous increase in the quarantine rates that, we show, can be tailored in a country-specific manner; for instance, we found the USA or Spain might require a 10 fold increase in testing/ quarantine rates compared to India to control the second wave post lockdown. Our data-driven modeling and analysis thus pave a way to understand and manipulate the infection dynamics during and post lockdown phases in various countries. The findings can also be used to strategize the testing and quarantine processes to manipulate the spread of the disease in the future.

scholarly journals Country-specific Optimization Strategy for Testing Through Contact Tracing Can Help Maintain a Low Reproduction Number (R_0) During Unlock

2021 ◽  
Author(s):  
Uddipan Sarma ◽  
Bhaswar Ghosh
Keyword(s):  
Positive Feedback ◽  
Feedback Loop ◽  
Reproduction Number ◽  
Epidemic Models ◽  
Contact Tracing ◽  
Positive Feedback Loop ◽  
Trade Off ◽  
Spread Of Infection ◽  
Country Specific ◽  
Infection Spread

Abstract In response to the COVID19 pandemics, many countries have implemented lockdowns in multiple phases to ensure social distancing and quarantining of the infected subjects as a first step to contain the infection spread. Subsequent unlocks to reopen the economies started next waves and imposed extra burden on quarantine to keep the reproduction number ( R0<1 ). Even with initial strict lockdowns and recent launching of vaccination programs, many countries are still struggling to contain the infection which suggests that revisiting the mechanism of lockdown-unlock implementation and simultaneous underpinning of the potential sources diluting the effort of such lockdowns could help better contain the spread of infection. Here, building epidemic models and analyzing the metadata of 50 countries, we first found that the estimated values of R0, adjusted w.r.t the distribution of medical facilities and virus clades, correlates strongly with the testing rates across countries. However, testing capacity of a country is limited by its medical resources, hence, as we demonstrate, optimizing a cost-benefit trade-off between testing rate and unlocking extents implemented in a country specific manner can help in devising the strategies of unlocking the economy. Our study delineates a strategy to optimize this trade-off by utilizing country specific infection spread parameters estimated in the epidemic models and implementing them in a stochastic agent based contact tracing models. The analysis provides a quantitative estimate of testing rates required to maintain a low for different extents of unlock. We further found that a small fraction of superspreaders can drastically increase the number of infected individuals even during lockdowns, primarily due to a switch-like response stemming from the implicit systems-level positive feedback loop driving the spread of infection. Our model suggests that with a country specific optimal combination of unlock extents and testing rates, R0 <1 can be stabilized during a pandemic like COVID19. To harness the benefit of improved testing rates and minimize the infection spread, strict social distancing norms to restrict the movement of superspreaders is necessary, such that onset of the positive feedback loop mediated exponential infection spread can be avoided.

scholarly journals Modeling the dynamics of COVID19 spread during and after social distancing: interpreting prolonged infection plateaus

2020 ◽  
Author(s):  
Natalia L. Komarova ◽  
Dominik Wodarz
Keyword(s):  
New York ◽  
Network Models ◽  
The United States ◽  
Social Distancing ◽  
Decline Phase ◽  
Intervention Measures ◽  
Infection Dynamics ◽  
Infection Models ◽  
Second Wave ◽  
Infection Spread

AbstractNon-pharmaceutical intervention measures, such as social distancing, have so far been the only means to slow the spread of COVID19. In the United States, strict social distancing has resulted in different types infection dynamics. In some states, such as New York, extensive infection spread was followed by a pronounced decline of infection levels. In other states, such as California, less infection spread occurred before strict social distancing, and a different pattern was observed. Instead of a pronounced infection decline, a long-lasting plateau is evident, characterized by similar daily new infection levels. While these plateau dynamics cannot be readily reproduced with standard SIR infection models, we show that network models, in which individuals and their social contacts are explicitly tracked, can reproduce the plateau if network connections are cut due to social distancing measures. The reason is that in networks characterized by a 2D spatial structure, infection tends to spread quadratically with time, but as edges are randomly removed, the infection spreads along nearly one-dimensional infection “corridors”, resulting in plateau dynamics. Interestingly, the plateau dynamics are predicted to eventually transition into an infection decline phase without any further increase in social distancing measures. Additionally, the models suggest that a potential second wave becomes significantly less pronounced if social distancing is only relaxed once the dynamics have transitioned to the decline phase. The network models analyzed here allow us to interpret and reconcile different infection dynamics during social distancing observed in various US states.

scholarly journals Analyzing the Effectiveness of COVID-19 Lockdown Policies Using the Time-Dependent Reproduction Number and the Regression Discontinuity Framework: Comparison between Countries

2021 ◽  
Vol 5 (1) ◽  
pp. 8
Author(s):  
Shangjun Liu ◽  
Tatiana Ermolieva ◽  
Guiying Cao ◽  
Gong Chen ◽  
Xiaoying Zheng
Keyword(s):  
Risk Perception ◽  
Real Time ◽  
Regression Discontinuity ◽  
Reproduction Number ◽  
Epidemic Models ◽  
Time Dependent ◽  
Time Reproduction ◽  
Long Period ◽  
Infection Dynamics ◽  
The Usa

This study compares the effectiveness of COVID-19 control policies on the virus’s spread and on the change of the infection dynamics in China, Germany, Austria, and the USA relying on a regression discontinuity in time and ‘earlyR’ epidemic models. The effectiveness of policies is measured by real-time reproduction number and cases counts. Comparison between the two lockdowns within each country showed the importance of people's risk perception for the effectiveness of the measures. Results suggest that restrictions applied for a long period or reintroduced later may cause at-tenuated effect on the circulation of the virus and the number of casualties.

scholarly journals Country-specific optimization strategy for testing through contact tracing can help maintain a low reproduction number ($$R_{0}$$) during unlock

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Uddipan Sarma ◽  
Bhaswar Ghosh
Keyword(s):  
Positive Feedback ◽  
Reproduction Number ◽  
Cost Benefit ◽  
Contact Tracing ◽  
Optimization Strategy ◽  
Trade Off ◽  
Social Distancing ◽  
Medical Facilities ◽  
Country Specific ◽  
Infection Spread

AbstractIn response to the COVID19 pandemic, many countries have implemented lockdowns in multiple phases to ensure social distancing and quarantining of the infected subjects. Subsequent unlocks to reopen the economies started next waves of infection and imposed an extra burden on quarantine to keep the reproduction number ($$R_{0}$$ R 0 ) < 1. However, most countries could not effectively contain the infection spread, suggesting identification of the potential sources weakening the effect of lockdowns could help design better informed lockdown-unlock cycles in the future. Here, through building quantitative epidemic models and analyzing the metadata of 50 countries from across the continents we first found that the estimated value of $$R_{0}$$ R 0 , adjusted w.r.t the distribution of medical facilities and virus clades correlates strongly with the testing rates in a country. Since the testing capacity of a country is limited by its medical resources, we investigated if a cost–benefit trade-off can be designed connecting testing rate and extent of unlocking. We present a strategy to optimize this trade-off in a country specific manner by providing a quantitative estimate of testing and quarantine rates required to allow different extents of unlocks while aiming to maintain $$R_{0} < 1$$ R 0 < 1 . We further show that a small fraction of superspreaders can dramatically increase the number of infected individuals even during strict lockdowns by strengthening the positive feedback loop driving infection spread. Harnessing the benefit of optimized country-specific testing rates would critically require minimizing the movement of these superspreaders via strict social distancing norms, such that the positive feedback driven switch-like exponential spread phase of infection can be avoided/delayed.

scholarly journals Fractional SIR-Model for Estimating Transmission Dynamics of COVID-19 in India

J ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 86-100
Author(s):  
Nita H. Shah ◽  
Ankush H. Suthar ◽  
Ekta N. Jayswal ◽  
Ankit Sikarwar
Keyword(s):  
Basic Reproduction Number ◽  
Reproduction Number ◽  
Transmission Rate ◽  
Sir Model ◽  
Time Dependent ◽  
Contact Rate ◽  
Distribution Maps ◽  
Fundamental Parameters ◽  
Different Order ◽  
The Basic Reproduction Number

In this article, a time-dependent susceptible-infected-recovered (SIR) model is constructed to investigate the transmission rate of COVID-19 in various regions of India. The model included the fundamental parameters on which the transmission rate of the infection is dependent, like the population density, contact rate, recovery rate, and intensity of the infection in the respective region. Looking at the great diversity in different geographic locations in India, we determined to calculate the basic reproduction number for all Indian districts based on the COVID-19 data till 7 July 2020. By preparing district-wise spatial distribution maps with the help of ArcGIS 10.2, the model was employed to show the effect of complete lockdown on the transmission rate of the COVID-19 infection in Indian districts. Moreover, with the model's transformation to the fractional ordered dynamical system, we found that the nature of the proposed SIR model is different for the different order of the systems. The sensitivity analysis of the basic reproduction number is done graphically which forecasts the change in the transmission rate of COVID-19 infection with change in different parameters. In the numerical simulation section, oscillations and variations in the model compartments are shown for two different situations, with and without lockdown.

scholarly journals Infection dynamics and persistence of hepatitis E virus on pig farms – a review

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
M. Meester ◽  
T. J. Tobias ◽  
M. Bouwknegt ◽  
N. E. Kusters ◽  
J. A. Stegeman ◽  
...  
Keyword(s):  
Risk Factors ◽  
Hepatitis E Virus ◽  
Risk Mitigation ◽  
Transmission Rate ◽  
Hepatitis E ◽  
Main Body ◽  
Genotype 3 ◽  
Infection Dynamics ◽  
Pig Farms ◽  
Slaughter Pigs

Abstract Background Hepatitis E virus (HEV) genotype 3 and 4 is a zoonosis that causes hepatitis in humans. Humans can become infected by consumption of pork or contact with pigs. Pigs are the main reservoir of the virus worldwide and the virus is present on most pig farms. Main body Though HEV is present on most farms, the proportion of infected pigs at slaughter and thus the level of exposure to consumers differs between farms and countries. Understanding the cause of that difference is necessary to install effective measures to lower HEV in pigs at slaughter. Here, HEV studies are reviewed that include infection dynamics of HEV in pigs and on farms, risk factors for HEV farm prevalence, and that describe mechanisms and sources that could generate persistence on farms. Most pigs become infected after maternal immunity has waned, at the end of the nursing or beginning of the fattening phase. Risk factors increasing the likelihood of a high farm prevalence or proportion of actively infected slaughter pigs comprise of factors such as farm demographics, internal and external biosecurity and immunomodulating coinfections. On-farm persistence of HEV is plausible, because of a high transmission rate and a constant influx of susceptible pigs. Environmental sources of HEV that enhance persistence are contaminated manure storages, water and fomites. Conclusion As HEV is persistently present on most pig farms, current risk mitigation should focus on lowering transmission within farms, especially between farm compartments. Yet, one should be aware of the paradox of increasing the proportion of actively infected pigs at slaughter by reducing transmission insufficiently. Vaccination of pigs may aid HEV control in the future.

scholarly journals Assessing Interventions against Coronavirus Disease 2019 (COVID-19) in Osaka, Japan: A Modeling Study

2021 ◽  
Vol 10 (6) ◽  
pp. 1256
Author(s):  
Ko Nakajo ◽  
Hiroshi Nishiura
Keyword(s):  
Model Comparison ◽  
Reproduction Number ◽  
State Of Emergency ◽  
Illness Onset ◽  
Epidemic Dynamics ◽  
Osaka Prefecture ◽  
Time Of Infection ◽  
Single Intervention ◽  
Second Wave ◽  
Combined Interventions

Estimation of the effective reproduction number, R(t), of coronavirus disease (COVID-19) in real-time is a continuing challenge. R(t) reflects the epidemic dynamics based on readily available illness onset data, and is useful for the planning and implementation of public health and social measures. In the present study, we proposed a method for computing the R(t) of COVID-19, and applied this method to the epidemic in Osaka prefecture from February to September 2020. We estimated R(t) as a function of the time of infection using the date of illness onset. The epidemic in Osaka came under control around 2 April during the first wave, and 26 July during the second wave. R(t) did not decline drastically following any single intervention. However, when multiple interventions were combined, the relative reductions in R(t) during the first and second waves were 70% and 51%, respectively. Although the second wave was brought under control without declaring a state of emergency, our model comparison indicated that relying on a single intervention would not be sufficient to reduce R(t) < 1. The outcome of the COVID-19 pandemic continues to rely on political leadership to swiftly design and implement combined interventions capable of broadly and appropriately reducing contacts.

scholarly journals Mathematical analysis of a measles transmission dynamics model in Bangladesh with double dose vaccination

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Md Abdul Kuddus ◽  
M. Mohiuddin ◽  
Azizur Rahman
Keyword(s):  
Basic Reproduction Number ◽  
Reproduction Number ◽  
Transmission Rate ◽  
Equilibrium Points ◽  
Rank Correlation ◽  
Dynamical Analysis ◽  
Model Parameters ◽  
Progression Rate ◽  
Double Dose ◽  
The Basic Reproduction Number

AbstractAlthough the availability of the measles vaccine, it is still epidemic in many countries globally, including Bangladesh. Eradication of measles needs to keep the basic reproduction number less than one $$(\mathrm{i}.\mathrm{e}. \, \, {\mathrm{R}}_{0}<1)$$ ( i . e . R 0 < 1 ) . This paper investigates a modified (SVEIR) measles compartmental model with double dose vaccination in Bangladesh to simulate the measles prevalence. We perform a dynamical analysis of the resulting system and find that the model contains two equilibrium points: a disease-free equilibrium and an endemic equilibrium. The disease will be died out if the basic reproduction number is less than one $$(\mathrm{i}.\mathrm{e}. \, \, {\mathrm{ R}}_{0}<1)$$ ( i . e . R 0 < 1 ) , and if greater than one $$(\mathrm{i}.\mathrm{e}. \, \, {\mathrm{R}}_{0}>1)$$ ( i . e . R 0 > 1 ) epidemic occurs. While using the Routh-Hurwitz criteria, the equilibria are found to be locally asymptotically stable under the former condition on $${\mathrm{R}}_{0}$$ R 0 . The partial rank correlation coefficients (PRCCs), a global sensitivity analysis method is used to compute $${\mathrm{R}}_{0}$$ R 0 and measles prevalence $$\left({\mathrm{I}}^{*}\right)$$ I ∗ with respect to the estimated and fitted model parameters. We found that the transmission rate $$(\upbeta )$$ ( β ) had the most significant influence on measles prevalence. Numerical simulations were carried out to commissions our analytical outcomes. These findings show that how progression rate, transmission rate and double dose vaccination rate affect the dynamics of measles prevalence. The information that we generate from this study may help government and public health professionals in making strategies to deal with the omissions of a measles outbreak and thus control and prevent an epidemic in Bangladesh.

scholarly journals Ectopic pregnancy: exploration of its global research architecture using density-equalising mapping and socioeconomic benchmarks

BMJ Open ◽  
2017 ◽  
Vol 7 (10) ◽  
pp. e018394 ◽  
Author(s):  
Dörthe Brüggmann ◽  
Jana Kollascheck ◽  
David Quarcoo ◽  
Michael H Bendels ◽  
Doris Klingelhöfer ◽  
...  
Keyword(s):  
Ectopic Pregnancy ◽  
Gdp Per Capita ◽  
Related Research ◽  
Depth Analysis ◽  
The Usa ◽  
Per Capita ◽  
The Uk ◽  
Research Architecture ◽  
Country Specific ◽  
Global Research

ObjectiveAbout 2% of all pregnancies are complicated by the implantation of the zygote outside the uterine cavity and termed ectopic pregnancy. Whereas a multitude of guidelines exists and related research is constantly growing, no thorough assessment of the global research architecture has been performed yet. Hence, we aim to assess the associated scientific activities in relation to geographical and chronological developments, existing research networks and socioeconomic parameters.DesignRetrospective, descriptive study.SettingOn the basis of the NewQIS platform, scientometric methods were combined with novel visualising techniques such as density-equalising mapping to assess the scientific output on ectopic pregnancy. Using the Web of Science, we identified all related entries from 1900 to 2012.Results8040 publications were analysed. The USA and the UK were dominating the field in regard to overall research activity (2612 and 723 publications), overall citation numbers and country-specific H-Indices (US: 80, UK: 42). Comparison to economic power of the most productive countries demonstrated that Israel invested more resources in ectopic pregnancy-related research than other nations (853.41 ectopic pregnancy-specific publications per 1000 billlion US$ gross domestic product (GDP)), followed by the UK (269.97). Relation to the GDP per capita index revealed 49.3 ectopic pregnancy-specific publications per US$1000 GDP per capita for the USA in contrast to 17.31 for the UK. Semiqualitative indices such as country-specific citation rates ranked Switzerland first (24.7 citations per ectopic pregnancy-specific publication), followed by the Scandinavian countries Finland and Sweden. Low-income countries did not exhibit significant research activities.ConclusionsThis is the first in-depth analysis of global ectopic pregnancy research since 1900. It offers unique insights into the global scientific landscape. Besides the USA and the UK, Scandinavian countries and Switzerland can also be regarded as leading nations with regard to their relative socioeconomic input.

scholarly journals The shifting landscape of tick-borne zoonoses: tick-borne encephalitis and Lyme borreliosis in Europe

2001 ◽  
Vol 356 (1411) ◽  
pp. 1045-1056 ◽  
Author(s):  
Sarah E. Randolph
Keyword(s):  
Lyme Borreliosis ◽  
Temporal Dynamics ◽  
Transmission Rate ◽  
Climate Change Scenarios ◽  
Vector Borne Diseases ◽  
Tick Borne Encephalitis ◽  
Tbe Virus ◽  
The Usa ◽  
Rate Of Emergence ◽  
The Baltic

The two major vector-borne diseases of northern temperate regions, tick-borne encephalitis (TBE) and Lyme borreliosis (LB), show very different epidemiological patterns, but both have increased significantly in incidence since the 1980s. Insight into the temporal dynamics of TBE, gained from statistical analysis of spatial patterns integrated with biological explanation, suggests that the recent increases in TBE cases in Central Europe and the Baltic States may have arisen largely from changes in human behaviour that have brought more people into contact with infected ticks. Under forecast climate change scenarios, it is predicted that enzootic cycles of TBE virus may not survive along the southern edge of their present range, e.g. in Slovenia, Croatia and Hungary, where case numbers are indeed decreasing. New foci, however, are predicted and have been observed in Scandinavia. At the same time, human impact on the landscape, increasing both the habitat and wildlife hosts of ticks, has allowed tick populations to multiply significantly. This probably accounts for a genuine emergence of LB, with its high potential transmission rate, in both the USA and Europe, although the rate of emergence has been exaggerated by improved surveillance and diagnosis.

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