scholarly journals Evaluating the effect of Chinese control measures on COVID-19 via temporal reproduction number estimation

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0246715
Author(s):  
Duanbing Chen ◽  
Tao Zhou
Keyword(s):  
Reproduction Number ◽  
Early Stage ◽  
Mainland China ◽  
Complete Information ◽  
Control Measures ◽  
Research Needs ◽  
Temporal Reproduction ◽  
Reproduction Numbers ◽  
Province Level ◽  
Level Analysis

Control measures are necessary to contain the spread of serious infectious diseases such as COVID-19, especially in its early stage. We propose to use temporal reproduction number an extension of effective reproduction number, to evaluate the efficacy of control measures, and establish a Monte-Carlo method to estimate the temporal reproduction number without complete information about symptom onsets. The province-level analysis indicates that the effective reproduction numbers of the majority of provinces in mainland China got down to < 1 just by one week from the setting of control measures, and the temporal reproduction number of the week [15 Feb, 21 Feb] is only about 0.18. It is therefore likely that Chinese control measures on COVID-19 are effective and efficient, though more research needs to be performed.

scholarly journals Modelling the Effectiveness of Epidemic Control Measures in Preventing the Transmission of COVID-19 in Malaysia

2020 ◽  
Vol 17 (15) ◽  
pp. 5509 ◽  
Author(s):  
Balvinder Singh Gill ◽  
Vivek Jason Jayaraj ◽  
Sarbhan Singh ◽  
Sumarni Mohd Ghazali ◽  
Yoon Ling Cheong ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Model Calibration ◽  
Reproduction Number ◽  
Close Contact ◽  
Movement Control ◽  
Control Measures ◽  
Seir Model ◽  
Epidemic Curve ◽  
Reproduction Numbers ◽  
Control Order

Malaysia is currently facing an outbreak of COVID-19. We aim to present the first study in Malaysia to report the reproduction numbers and develop a mathematical model forecasting COVID-19 transmission by including isolation, quarantine, and movement control measures. We utilized a susceptible, exposed, infectious, and recovered (SEIR) model by incorporating isolation, quarantine, and movement control order (MCO) taken in Malaysia. The simulations were fitted into the Malaysian COVID-19 active case numbers, allowing approximation of parameters consisting of probability of transmission per contact (β), average number of contacts per day per case (ζ), and proportion of close-contact traced per day (q). The effective reproduction number (Rt) was also determined through this model. Our model calibration estimated that (β), (ζ), and (q) were 0.052, 25 persons, and 0.23, respectively. The (Rt) was estimated to be 1.68. MCO measures reduce the peak number of active COVID-19 cases by 99.1% and reduce (ζ) from 25 (pre-MCO) to 7 (during MCO). The flattening of the epidemic curve was also observed with the implementation of these control measures. We conclude that isolation, quarantine, and MCO measures are essential to break the transmission of COVID-19 in Malaysia.

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.

scholarly journals The spatial transmission of SARS-CoV-2 in China under the prevention and control measures at the early outbreak

2021 ◽  
Vol 79 (1) ◽  
Author(s):  
Jianli Liu ◽  
Yuan Zhou ◽  
Chuanyu Ye ◽  
Guangming Zhang ◽  
Feng Zhang ◽  
...  
Keyword(s):  
Basic Reproduction Number ◽  
Prevention And Control ◽  
Reproduction Number ◽  
Early Stage ◽  
Chinese Mainland ◽  
Hubei Province ◽  
Control Measures ◽  
Provincial Level ◽  
Prevention And Control Measures ◽  
And Control

Abstract Background Since severe acute respiratory syndrome coronavirus, 2 (SARS-CoV-2) was firstly reported in Wuhan City, China in December 2019, Novel Coronavirus Disease 2019 (COVID-19) that is caused by SARS-CoV-2 is predominantly spread from person-to-person on worldwide scales. Now, COVID-19 is a non-traditional and major public health issue the world is facing, and the outbreak is a global pandemic. The strict prevention and control measures have mitigated the spread of SARS-CoV-2 and shown positive changes with important progress in China. But prevention and control tasks remain arduous for the world. The objective of this study is to discuss the difference of spatial transmission characteristics of COVID-19 in China at the early outbreak stage with resolute efforts. Simultaneously, the COVID-19 trend of China at the early time was described from the statistical perspective using a mathematical model to evaluate the effectiveness of the prevention and control measures. Methods In this study, the accumulated number of confirmed cases publicly reported by the National Health Committee of the People’s Republic of China (CNHC) from January 20 to February 11, 2020, were grouped into three partly overlapping regions: Chinese mainland including Hubei province, Hubei province alone, and the other 30 provincial-level regions on Chinese mainland excluding Hubei province, respectively. A generalized-growth model (GGM) was used to estimate the basic reproduction number to evaluate the transmissibility in different spatial locations. The prevention and control of COVID-19 in the early stage were analyzed based on the number of new cases of confirmed infections daily reported. Results Results indicated that the accumulated number of confirmed cases reported from January 20 to February 11, 2020, is well described by the GGM model with a larger correlation coefficient than 0.99. When the accumulated number of confirmed cases is well fitted by an exponential function, the basic reproduction number of COVID-19 of the 31 provincial-level regions on the Chinese mainland, Hubei province, and the other 30 provincial-level regions on the Chinese mainland excluding Hubei province, is 2.68, 6.46 and 2.18, respectively. The consecutive decline of the new confirmed cases indicated that the prevention and control measures taken by the Chinese government have contained the spread of SARS-CoV-2 in a short period. Conclusions The estimated basic reproduction number thorough GGM model can reflect the spatial difference of SARS-CoV-2 transmission in China at the early stage. The strict prevention and control measures of SARS-CoV-2 taken at the early outbreak can effectively reduce the new confirmed cases outside Hubei and have mitigated the spread and yielded positive results since February 2, 2020. The research results indicated that the outbreak of COVID-19 in China was sustaining localized at the early outbreak stage and has been gradually curbed by China’s resolute efforts.

scholarly journals Evolution of effective serial interval of SARS-CoV-2 by non-pharmaceutical interventions

2020 ◽  
Author(s):  
Sheikh Taslim Ali ◽  
Lin Wang ◽  
Eric H. Y. Lau ◽  
Xiao-Ke Xu ◽  
Zhanwei Du ◽  
...  
Keyword(s):  
Mainland China ◽  
Time Estimation ◽  
Control Measures ◽  
Reproduction Numbers ◽  
Serial Interval ◽  
Real Time Estimation ◽  
Definition Of ◽  
Novel Coronavirus ◽  
The Impact ◽  
Pharmaceutical Interventions

Abstract Studies of novel coronavirus disease (COVID-19) have reported varying estimates of epidemiological parameters such as serial intervals and reproduction numbers. By compiling a unique line-list database of transmission pairs in mainland China, we demonstrated that serial intervals of COVID-19 have shortened substantially from a mean of 7.8 days to 2.6 days within a month. This change is driven by enhanced non-pharmaceutical interventions, in particular case isolation. We also demonstrated that using real-time estimation of serial intervals allowing for variation over time would provide more accurate estimates of reproduction numbers, than by using conventional definition of fixed serial interval distributions. These findings are essential to improve the assessment of transmission dynamics, forecasting future incidence, and estimating the impact of control measures.

scholarly journals Viral infection and Transmission in a large well-traced outbreak caused by the Delta SARS-CoV-2 variant

2021 ◽  
Author(s):  
Baisheng Li ◽  
Aiping Deng ◽  
Kuibiao Li ◽  
Yao Hu ◽  
Zhencui Li ◽  
...  
Keyword(s):  
Index Case ◽  
Early Stage ◽  
Mainland China ◽  
Epidemiological Data ◽  
Control Measures ◽  
Sequencing Data ◽  
Replication Rate ◽  
Single Nucleotide Variants ◽  
Single Nucleotide ◽  
Local Transmission

We report the first local transmission of the Delta SARS-CoV-2 variant in mainland China. All 167 infections could be traced back to the first index case. The investigation on daily sequential PCR testing of the quarantined subjects indicated the viral load of the first positive test of Delta infections was ~1000 times higher than that of the 19A/19B strains infections back in the initial epidemic wave of 2020, suggesting the potential faster viral replication rate and more infectiousness of the Delta variant at the early stage of the infection. The 126 high-quality sequencing data and reliable epidemiological data indicated some minor intra-host single nucleotide variants (iSNVs) could be transmitted between hosts and finally fixed in the virus population during the outbreak. The minor iSNVs transmission between donor-recipient contribute at least 4 of 31 substitutions identified in the outbreak suggesting some iSNVs more likely to arise and reach fixation when the virus spread rapidly. Disease control measures, including the frequency of population testing, quarantine in pre-symptomatic phase and enhancing the genetic surveillance should be adjusted to account for the increasing prevalence of the Delta variant at global level.

scholarly journals Comparison of Different Approaches in Estimating Initial Reproduction Number of SARS-CoV-2 in the Islamic Republic of Iran

2021 ◽  
Vol 8 (4) ◽  
Author(s):  
Nasrin Talkhi ◽  
Nayereh Esmaeilzadeh ◽  
Mohammad Taghi Shakeri ◽  
Zahra Pasdar
Keyword(s):  
Disease Transmission ◽  
Reproduction Number ◽  
Early Stage ◽  
Control Measures ◽  
Epidemic Threshold ◽  
Fitting Method ◽  
Rate Maximum ◽  
Islamic Republic Of Iran ◽  
Best Fitting ◽  
Fitting In

Background: The basic reproduction number (R0) is an epidemic threshold parameter that indicates the magnitude of disease transmission and thus allows suggestions for the planning of control measures. Objectives: Our aim in this study was to compare different approaches for estimating R0 in the early stage of the SARS-CoV-2 outbreak and discern the best-fitting model. Methods: The dataset was derived from cumulative laboratory-confirmed COVID-19 cases from 26th February to 30th May 2020 in Iran. The methods of exponential growth (EG) rate, maximum likelihood (ML), time-dependent (TD) reproduction number, attack rate (AR), and sequential Bayesian (SB) model were used. The gamma distribution (mean 4.41 ± 3.17 days) was used for serial interval (SI) distribution. The best-fitting method was selected according to the lowest root mean square error (RMSE). Results: We obtained the following estimated R0 [95% confidence interval]: 1.55 [1.54; 1.55], 1.46 [1.45; 1.46], 1.31 [1.30; 1.32], and 1.40 [1.39; 1.41] using EG, ML, TD, and SB methods, respectively. Additionally, the EG and ML methods showed an overestimation of R0, and the SB method showed to be under-fitting in the estimation of R0. The AR method estimated R0 equal to one. The TD method had the lowest RMSE. Conclusions: The simulated and actual R0 of TD showed that this method had a good fit for actual data and the lowest RMSE. Therefore, the TD method is the most appropriate method with the best performance in estimating actual R0 values.

scholarly journals Serial interval of SARS-CoV-2 was shortened over time by nonpharmaceutical interventions

Science ◽  
2020 ◽  
Vol 369 (6507) ◽  
pp. 1106-1109 ◽  
Author(s):  
Sheikh Taslim Ali ◽  
Lin Wang ◽  
Eric H. Y. Lau ◽  
Xiao-Ke Xu ◽  
Zhanwei Du ◽  
...  
Keyword(s):  
Mainland China ◽  
Time Estimation ◽  
Control Measures ◽  
Illness Onset ◽  
Reproduction Numbers ◽  
Serial Interval ◽  
Novel Coronavirus ◽  
Nonpharmaceutical Interventions ◽  
The Impact ◽  
Over Time

Studies of novel coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), have reported varying estimates of epidemiological parameters, including serial interval distributions—i.e., the time between illness onset in successive cases in a transmission chain—and reproduction numbers. By compiling a line-list database of transmission pairs in mainland China, we show that mean serial intervals of COVID-19 shortened substantially from 7.8 to 2.6 days within a month (9 January to 13 February 2020). This change was driven by enhanced nonpharmaceutical interventions, particularly case isolation. We also show that using real-time estimation of serial intervals allowing for variation over time provides more accurate estimates of reproduction numbers than using conventionally fixed serial interval distributions. These findings could improve our ability to assess transmission dynamics, forecast future incidence, and estimate the impact of control measures.

scholarly journals Modeling and reviewing analysis of the COVID-19 epidemic in Algeria with diagnostic shadow

2021 ◽  
Author(s):  
Jiwei Jia ◽  
Siyu Liu ◽  
Yawen Liu ◽  
Ruitong Shan ◽  
Khaled Zennir ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Reproduction Number ◽  
Control Strategies ◽  
Control Measures ◽  
Effective Control ◽  
Reproduction Numbers ◽  
Epidemic Dynamic ◽  
Reported Data ◽  
Parameter Values ◽  
Research Period

In this paper, we formulate a special epidemic dynamic model to describe the transmission of COVID-19 in Algeria. We derive the threshold parameter control reproduction number (R0c ), and present the effective control reproduction number (Rc(t)) as a real-time index for evaluating the epidemic under different control strategies. Due to the limitation of the reported data, we redefine the number of accumulative confirmed cases with diagnostic shadow and then use the processed data to do the optimal numerical simulations. According to the control measures, we divide the whole research period into six stages. And then the corresponding medical resource estimations and the average effective control reproduction numbers for each stage are given. Meanwhile, we use the parameter values which are obtained from the optimal numerical simulations to forecast the whole epidemic tendency under different control strategies.

scholarly journals The importance of the timing of quarantine measures before symptom onset to prevent COVID-19 outbreaks - illustrated by Hong Kong’s intervention model

2020 ◽  
Author(s):  
Hsiang-Yu Yuan ◽  
Guiyuan Han ◽  
Hsiangkuo Yuan ◽  
Susanne Pfeiffer ◽  
Axiu Mao ◽  
...  
Keyword(s):  
Hong Kong ◽  
Symptom Onset ◽  
Reproduction Number ◽  
Model Fitting ◽  
Mainland China ◽  
Control Measures ◽  
Rapid Expansion ◽  
Transmission Dynamics ◽  
Population Immunity ◽  
Key Factor

AbstractBackgroundThe rapid expansion of the current COVID-19 outbreak has caused a global pandemic but how quarantine-based measures can prevent or suppress an outbreak without other more intrusive interventions has not yet been determined. Hong Kong had a massive influx of travellers from mainland China, where the outbreak began, during the early expansion period coinciding with the Lunar New Year festival; however, the spread of the virus has been relatively limited even without imposing severe control measures, such as a full city lockdown. Understanding how quarantine measures in Hong Kong were effective in limiting community spread can provide us with valuable insights into how to suppress an outbreak. However, challenges exist in evaluating the effects of quarantine on COVID-19 transmission dynamics in Hong Kong due to the fact that the effects of border control have to be also taken into account.MethodsWe have developed a two-layered susceptible-exposed-infectious-quarantined-recovered (SEIQR) meta-population model which can estimate the effects of quarantine on virus transmissibility after stratifying infections into imported and subsequent community infections, in a region closely connected to the outbreak’s source. We fitted the model to both imported and local confirmed case data with symptom onset from 18 January to 29 February 2020 in Hong Kong, together with daily transportation data and the transmission dynamics of COVID-19 from Wuhan and mainland China. After model fitting, epidemiological parameters and the timing of the start of quarantine for infected cases were estimated.ResultsThe model estimated that the reproduction number of COVID-19 in Hong Kong was 0.76 (95% CI, 0.66 to 0.86), achieved through quarantining infected cases −0.57 days (95% CI, −4.21 − 3.88) relative to symptom onset, with an estimated incubation time of 5.43 days (95% CI, 1.30 − 9.47). However, if delaying the quarantine start by more than 1.43 days, the reproduction number would be greater than one, making community spread more likely. The model also determined the timing of the start of quarantine necessary in order to suppress an outbreak in the presence of population immunity.ConclusionThe results suggest that the early quarantine for infected cases before symptom onset is a key factor to prevent COVID-19 outbreak.

scholarly journals Lessons drawn from China and South Korea for managing COVID-19 epidemic: insights from a comparative modeling study

2020 ◽  
Author(s):  
Biao Tang ◽  
Fan Xia ◽  
Nicola Luigi Bragazzi ◽  
Xia Wang ◽  
Sha He ◽  
...  
Keyword(s):  
South Korea ◽  
Disease Transmission ◽  
Reproduction Number ◽  
Mainland China ◽  
Guangdong Province ◽  
Comparative Modeling ◽  
Integrated Approach ◽  
Reproduction Numbers ◽  
Serial Interval ◽  
Dynamics Models

AbstractWe conducted a comparative study of COVID-19 epidemic in three different settings: mainland China, the Guangdong province of China and South Korea, by formulating two disease transmission dynamics models incorporating epidemic characteristics and setting-specific interventions, and fitting the models to multi-source data to identify initial and effective reproduction numbers and evaluate effectiveness of interventions. We estimated the initial basic reproduction number for South Korea, the Guangdong province and mainland China as 2.6 (95% confidence interval (CI): (2.5, 2.7)), 3.0 (95%CI: (2.6, 3.3)) and 3.8 (95%CI: (3.5,4.2)), respectively, given a serial interval with mean of 5 days with standard deviation of 3 days. We found that the effective reproduction number for the Guangdong province and mainland China has fallen below the threshold 1 since February 8th and 18th respectively, while the effective reproduction number for South Korea remains high, suggesting that the interventions implemented need to be enhanced in order to halt further infections. We also project the epidemic trend in South Korea under different scenarios where a portion or the entirety of the integrated package of interventions in China is used. We show that a coherent and integrated approach with stringent public health interventions is the key to the success of containing the epidemic in China and specially its provinces outside its epicenter, and we show that this approach can also be effective to mitigate the burden of the COVID-19 epidemic in South Korea. The experience of outbreak control in mainland China should be a guiding reference for the rest of the world including South Korea.

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