scholarly journals Changes in the serial interval and transmission dynamics associated with the SARS-CoV-2 Delta variant in South Korea

2021 ◽  
Author(s):  
Sukhyun Ryu ◽  
Dasom Kim ◽  
Jun-Sik Lim ◽  
Sheikh Taslim Ali ◽  
Benjamin J Cowling
Keyword(s):  
South Korea ◽  
Transmission Dynamics ◽  
Serial Interval ◽  
The Mean

We estimated the mean serial interval and superspreading potential for the Delta variant SARS-CoV-2. As the Delta variant increased in prevalence, the mean serial interval declined from 4.0 to 2.5 days. However, the risk of superspreading events was similar, as 25% to 27% of cases seeded 80% of all transmission.

scholarly journals Clinical onset serial interval and diagnostic serial interval of SARS-CoV-2/COVID-19 in South Korea

2020 ◽  
Author(s):  
Sofia K. Mettler ◽  
Marloes H. Maathuis
Keyword(s):  
South Korea ◽  
Bootstrap Method ◽  
Sample Analysis ◽  
Bootstrap Confidence Intervals ◽  
Clinical Onset ◽  
Serial Interval ◽  
The Mean ◽  
The Difference ◽  
A Chain ◽  
Project Data

BACKGROUNDThe clinical onset serial interval, or the time between the onset of symptoms in successive cases in a chain of infection, is often used as a measurable proxy for the transmission serial interval of an infectious disease. Current estimates of the mean clinical onset serial interval of COVID-19 range from 3.96 to 7.5 days. In this article, we define the diagnostic serial interval as the time between the diagnosis dates of the infector and infectee. We study and compare the clinical onset and diagnostic serial intervals of SARS-CoV-2/COVID-19 in South Korea.METHODSAnalyzing the DS4C project data which summarize information on SARS-CoV-2/COVID-19 cases reported by regional governments in South Korea, we estimate the means of the clinical onset serial interval, the diagnostic serial interval and the difference between the two. We use the balanced cluster bootstrap method to construct 95% bootstrap confidence intervals.RESULTSThe mean clinical onset serial interval and mean diagnostic serial interval were estimated to be 3.58 days (95% CI: 2.62, 4.53) and 3.68 days (95% CI: 3.14, 4.22), respectively. A matched sample analysis showed that the diagnostic serial interval was significantly shorter than the clinical onset serial interval (estimated mean difference −1.17 days, 95% CI: −2.26, −0.09).CONCLUSIONSThe short diagnostic serial interval of SARS-CoV-2/COVID-19 in South Korea may explain why South Korea was able to contain the COVID-19 outbreak and avoid high mortality. We conjecture that the mean diagnostic serial interval may serve as a predictor for the success of a country’s containment efforts.

scholarly journals Serial Interval and Transmission Dynamics during SARS-CoV-2 Delta Variant Predominance, South Korea

2022 ◽  
Vol 28 (2) ◽  
Author(s):  
Sukhyun Ryu ◽  
Dasom Kim ◽  
Jun-Sik Lim ◽  
Sheikh Taslim Ali ◽  
Benjamin J. Cowling
Keyword(s):  
South Korea ◽  
Transmission Dynamics ◽  
Serial Interval

scholarly journals Serial interval and basic reproduction number of SARS-CoV-2 Omicron variant in South Korea

2021 ◽  
Author(s):  
Dasom Kim ◽  
Jisoo Jo ◽  
Jun-Sik Lim ◽  
Sukhyun Ryu
Keyword(s):  
South Korea ◽  
Basic Reproduction Number ◽  
Reproduction Number ◽  
Credible Interval ◽  
Serial Interval ◽  
Community Transmission ◽  
The Mean ◽  
The Basic Reproduction Number

South Korea is experiencing the community transmission of the SARS-CoV-2 Omicron variant (B.1.1.529). We estimated that the mean of the serial interval was 2.22 days, and the basic reproduction number was 1.90 (95% Credible Interval, 1.50-2.43) for the Omicron variant outbreak in South Korea.

scholarly journals Transmission dynamics and epidemiological characteristics of Delta variant infections in China

2021 ◽  
Author(s):  
Min Kang ◽  
Hualei Xin ◽  
Jun Yuan ◽  
Sheikh Taslim Ali ◽  
Zimian Liang ◽  
...  
Keyword(s):  
Viral Load ◽  
Confidence Interval ◽  
Southern China ◽  
Transmission Dynamics ◽  
Wild Type ◽  
Viral Loads ◽  
Serial Interval ◽  
The Mean ◽  
Epidemiological Characteristics ◽  
Close Contacts

Background: The Delta variant of SARS-CoV-2 has become predominant globally. We evaluated the transmission dynamics and epidemiological characteristics of the Delta variant in an outbreak in southern China. Methods: Data on confirmed cases and their close contacts were retrospectively collected from the outbreak that occurred in Guangdong, China in May-June 2021. Key epidemiological parameters, temporal trend of viral loads and secondary attack rates were estimated and compared between the Delta variant and the wild-type SARS-CoV-2 virus. We also evaluated the association of vaccination with viral load and transmission. Results: We identified 167 patients infected with the Delta variant in the Guangdong outbreak. The mean estimates of the latent period and the incubation period were 4.0 days and 5.8 days, respectively. A relatively higher viral load was observed in Delta cases than in wild-type infections. The secondary attack rate among close contacts of Delta cases was 1.4%, and 73.9% (95% confidence interval: 67.2%, 81.3%) of the transmissions occurred before onset. Index cases without vaccination (OR: 2.84, 95% confidence interval: 1.19, 8.45) or with one dose of vaccination (OR: 6.02, 95% confidence interval: 2.45, 18.16) were more likely to transmit infection to their contacts than those who had received 2 doses of vaccination. Discussion: Patients infected with the Delta variant had more rapid symptom onset. The shorter and time-varying serial interval should be accounted in estimation of reproductive numbers. The higher viral load and higher risk of pre-symptomatic transmission indicated the challenges in control of infections with the Delta variant.

scholarly journals Assessing the potential impact of transmission during prolonged viral shedding on the effect of lockdown relaxation on COVID-19

2020 ◽  
Author(s):  
Burcu Tepekule ◽  
Anthony Hauser ◽  
Viacheslav N. Kachalov ◽  
Sara Andresen ◽  
Thomas Scheier ◽  
...  
Keyword(s):  
Transmission Dynamics ◽  
Epidemiological Modeling ◽  
Hospital Capacity ◽  
Viral Shedding ◽  
Plausible Model ◽  
Serial Interval ◽  
The Mean ◽  
Potential Impact ◽  
Key Parameter

AbstractA key parameter in epidemiological modeling which characterizes the spread of an infectious disease is the mean serial interval. There is increasing evidence supporting a prolonged viral shedding window for COVID-19, but the transmissibility in this phase is unclear. Based on this, we build a model including an additional compartment of infectious individuals who stay infectious for a longer duration than the reported serial interval, but with infectivity reduced to varying degrees. We find that such an assumption also yields a plausible model in explaining the data observed so far, but has different implications for the future predictions in case of a gradual easing on the lockdown measures. Considering the role of modeling in important decisions such as easing lockdown measures and adjusting hospital capacity, we believe that it is critically important to consider a chronically infectious population as an alternative modeling approach to better interpret the transmission dynamics of COVID-19.

scholarly journals OP0073 RISK OF DEVELOPING RHEUMATIC DISEASES IN PATIENTS WITH PALINDROMIC RHEUMATISM IN SOUTH KOREA: A NATION-WIDE POPULATION-BASED STUDY

2020 ◽  
Vol 79 (Suppl 1) ◽  
pp. 49.2-49
Author(s):  
J. K. Ahn ◽  
J. Hwang ◽  
J. Lee ◽  
H. Kim ◽  
G. H. Seo
Keyword(s):  
Health Insurance ◽  
South Korea ◽  
Rheumatic Diseases ◽  
Index Date ◽  
Claims Data ◽  
Population Based ◽  
Palindromic Rheumatism ◽  
Psoriatic Arthropathy ◽  
Increased Risk ◽  
The Mean

Background:Palindromic rheumatism (PR) has known to be three patterns of disease course: clinical remission of attacks, persistent attacks, and evolution to chronic arthritis or systemic disease. The spectrum in progression to chronic diseases of PR, however, is quite variable; rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), systemic sclerosis (SSc), Sjögren’s syndrome (SjS), ankylosing spondylitis (AS), relapsing polychondritis (RP), Behçet’s disease (BD), sarcoidosis, and psoriatic spondylitis and arthropathy. Because of the small numbers in case-control studies and too aged investigations, now we needs to shed new light on the fate of PR.Objectives:The aim was to investigate the epidemiology of PR and the risk of developing various rheumatic diseases compared with non-PR individuals, employing the National Health Insurance Service (NHIS) medical claims data, which covers all medical institutions of South Korea.Methods:The study used 2007-2018 claims data from the Korean Health Insurance Review and Assessment Service (HIRA). The identified 19,724 PR patients from 2010 to 2016 were assessed for the incidence rate (IR) compared with the population in the given year by 100,000 person-year (py). The date of diagnosis was the index date. After matching with non-PR individuals (1:10) for age, sex and the year of index date, we calculated the hazard ratios (HRs) with 95% confidence intervals (CIs). The risk of developing the various rheumatic diseases and adult immunodeficiency syndrome (AIDS) as the outcome diseases in PR cohort was estimated. This risk was compared with that of matched non-PR cohort.Results:Of 19,724 PR patients (8,665 males and 11,059 females), the mean age was 50.2 ± 14.9 years (47.7 ± 14.4 years in males and 52.6 ± 14.9 years in females,p< 0.001). The ratio of male to female patients with PR was approximately 1:1.28. The annual IR of PR was 7.02 (6.92-7.12) per 100,000 py (6.22 (6.09-6.35) and 7.80 (7.66-7.95) per 100,000 py in males and females, respectively). The mean duration to develop the outcome diseases was significantly shorter in PR cohort compared that of non-PR cohort (19.4 vs. 35.8 months,p< 0.001). The most common outcome disease was RA (7.34% of PR patients; 80.0% of total outcome diseases), followed by AS, SLE, BD, SjS, MCTD, DM/PM, SSc, RP, psoriatic arthropathy, and AIDS in PR cohort. The patients with PR had an increased risk of RA (HR 46.6, 95% CI [41.1-52.7]), psoriatic arthropathy (44.79 [15.2-132.4]), SLE (24.5 [16.2-37.2]), MCTD (22.0 [7.7-63.3]), BD (21.0 [13.8-32.1]), SjS (12.4 [8.5-17.9]), AS (9.0 [6.7-12.2]), DM/PM (6.1 [2.6-14.8]), and SSc (3.8 [1.5-9.6]) but not of AIDS. The risk of developing RA was greater in male patients (HR 58.9, 95% CI [45.6-76.2] vs. 43.2 [37.4-49.8],pfor interaction = 0.037) while female patients encountered a higher risk of developing AS (15.8 [8.9-28.1] vs. 7.2 [5.0-10.3],pfor interaction = 0.023). The risk of developing RA, SLE, SjS, and BD were significantly more highly affected in younger age (pfor interaction < 0.001, = 0.003, 0.002, and 0.017, at each).Conclusion:This nationwide, population-based cohort study demonstrated that patients with PR had an increased risk of developing various rheumatic diseases, not only RA but also psoriatic arthropathy. Therefore, patients with PR needs to be cautiously followed up for their potential of diverse outcome other than RA: RA, SLE, SjS, and BD in younger patients, RA in males, and AS in females, in particular.Disclosure of Interests:None declared

scholarly journals Rapid review of available evidence on the serial interval and generation time of COVID-19

BMJ Open ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. e040263
Author(s):  
John Griffin ◽  
Miriam Casey ◽  
Áine Collins ◽  
Kevin Hunt ◽  
David McEvoy ◽  
...  
Keyword(s):  
Generation Time ◽  
Social Contact ◽  
Careful Consideration ◽  
Rapid Review ◽  
Eligibility Criteria ◽  
Reproduction Numbers ◽  
Serial Interval ◽  
Scientific Papers ◽  
The Mean ◽  
Parameter Values

The serial interval is the time between symptom onsets in an infector–infectee pair. The generation time, also known as the generation interval, is the time between infection events in an infector–infectee pair. The serial interval and the generation time are key parameters for assessing the dynamics of a disease. A number of scientific papers reported information pertaining to the serial interval and/or generation time for COVID-19. Objective Conduct a review of available evidence to advise on appropriate parameter values for serial interval and generation time in national COVID-19 transmission models for Ireland and on methodological issues relating to those parameters. Methods We conducted a rapid review of the literature covering the period 1 January 2020 and 21 August 2020, following predefined eligibility criteria. Forty scientific papers met our inclusion criteria and were included in the review. Results The mean of the serial interval ranged from 3.03 to 7.6 days, based on 38 estimates, and the median from 1.0 to 6.0 days (based on 15 estimates). Only three estimates were provided for the mean of the generation time. These ranged from 3.95 to 5.20 days. One estimate of 5.0 days was provided for the median of the generation time. Discussion Estimates of the serial interval and the generation time are very dependent on the specific factors that apply at the time that the data are collected, including the level of social contact. Consequently, the estimates may not be entirely relevant to other environments. Therefore, local estimates should be obtained as soon as possible. Careful consideration should be given to the methodology that is used. Real-time estimations of the serial interval/generation time, allowing for variations over time, may provide more accurate estimates of reproduction numbers than using conventionally fixed serial interval/generation time distributions.

scholarly journals Subcritical Transmission in the Early Stage of COVID-19 in Korea

2021 ◽  
Vol 18 (3) ◽  
pp. 1265
Author(s):  
Yong Sul Won ◽  
Jong-Hoon Kim ◽  
Chi Young Ahn ◽  
Hyojung Lee
Keyword(s):  
Incubation Period ◽  
Early Stage ◽  
Probability Distributions ◽  
Likelihood Estimation ◽  
Contact Tracing ◽  
Statistical Characterization ◽  
Serial Interval ◽  
Imported Cases ◽  
The Mean ◽  
Reporting Delays

While the coronavirus disease 2019 (COVID-19) outbreak has been ongoing in Korea since January 2020, there were limited transmissions during the early stages of the outbreak. In the present study, we aimed to provide a statistical characterization of COVID-19 transmissions that led to this small outbreak. We collated the individual data of the first 28 confirmed cases reported from 20 January to 10 February 2020. We estimated key epidemiological parameters such as reporting delay (i.e., time from symptom onset to confirmation), incubation period, and serial interval by fitting probability distributions to the data based on the maximum likelihood estimation. We also estimated the basic reproduction number (R0) using the renewal equation, which allows for the transmissibility to differ between imported and locally transmitted cases. There were 16 imported and 12 locally transmitted cases, and secondary transmissions per case were higher for the imported cases than the locally transmitted cases (nine vs. three cases). The mean reporting delays were estimated to be 6.76 days (95% CI: 4.53, 9.28) and 2.57 days (95% CI: 1.57, 4.23) for imported and locally transmitted cases, respectively. The mean incubation period was estimated to be 5.53 days (95% CI: 3.98, 8.09) and was shorter than the mean serial interval of 6.45 days (95% CI: 4.32, 9.65). The R0 was estimated to be 0.40 (95% CI: 0.16, 0.99), accounting for the local and imported cases. The fewer secondary cases and shorter reporting delays for the locally transmitted cases suggest that contact tracing of imported cases was effective at reducing further transmissions, which helped to keep R0 below one and the overall transmissions small.

scholarly journals Evolving epidemiology of novel coronavirus diseases 2019 and possible interruption of local transmission outside Hubei Province in China: a descriptive and modeling study

2020 ◽  
Author(s):  
Juanjuan Zhang ◽  
Maria Litvinova ◽  
Wei Wang ◽  
Yan Wang ◽  
Xiaowei Deng ◽  
...  
Keyword(s):  
Age Groups ◽  
Mainland China ◽  
The Elderly ◽  
Hubei Province ◽  
Epidemic Threshold ◽  
Epidemic Dynamics ◽  
Serial Interval ◽  
The Mean ◽  
Novel Coronavirus ◽  
Local Transmission

AbstractBackgroundThe COVID-19 epidemic originated in Wuhan City of Hubei Province in December 2019 and has spread throughout China. Understanding the fast evolving epidemiology and transmission dynamics of the outbreak beyond Hubei would provide timely information to guide intervention policy.MethodsWe collected individual information on 8,579 laboratory-confirmed cases from official publically sources reported outside Hubei in mainland China, as of February 17, 2020. We estimated the temporal variation of the demographic characteristics of cases and key time-to-event intervals. We used a Bayesian approach to estimate the dynamics of the net reproduction number (Rt) at the provincial level.ResultsThe median age of the cases was 44 years, with an increasing of cases in younger age groups and the elderly as the epidemic progressed. The delay from symptom onset to hospital admission decreased from 4.4 days (95%CI: 0.0-14.0) until January 27 to 2.6 days (0.0-9.0) from January 28 to February 17. The mean incubation period was estimated at 5.2 days (1.8-12.4) and the mean serial interval at 5.1 days (1.3-11.6). The epidemic dynamics in provinces outside Hubei was highly variable, but consistently included a mix of case importations and local transmission. We estimate that the epidemic was self-sustained for less than three weeks with Rt reaching peaks between 1.40 (1.04-1.85) in Shenzhen City of Guangdong Province and 2.17 (1.69-2.76) in Shandong Province. In all the analyzed locations (n=10) Rt was estimated to be below the epidemic threshold since the end of January.ConclusionOur findings suggest that the strict containment measures and movement restrictions in place may contribute to the interruption of local COVID-19 transmission outside Hubei Province. The shorter serial interval estimated here implies that transmissibility is not as high as initial estimates suggested.

scholarly journals Transmission dynamics of the delta variant of SARS-CoV-2 infections in Daejeon, South Korea

2021 ◽  
Author(s):  
Hari Hwang ◽  
Jun-Sik Lim ◽  
Sun-Ah Song ◽  
Chiara Achangwa ◽  
Woobeom Sim ◽  
...  
Keyword(s):  
South Korea ◽  
Symptom Onset ◽  
Credible Interval ◽  
Transmission Dynamics ◽  
Contact Tracing ◽  
Nasopharyngeal Swab ◽  
Strict Adherence ◽  
Virus Shedding ◽  
Viral Shedding ◽  
Asymptomatic Patients

Abstract Background The delta variant of SARS-CoV-2 is now the predominant variant worldwide. However, its transmission dynamics remain unclear. Methods We analyzed all case patients in local clusters and temporal patterns of viral shedding using contact tracing data from 405 cases associated with the delta variant of SARS-CoV-2 between 22 June and 31 July 2021 in Daejeon, South Korea. Results Overall, half of the cases were aged under 19 years, and 20% were asymptomatic at the time of epidemiological investigation. We estimated the mean serial interval as 3.26 days (95% credible interval 2.92, 3.60), and 12% of the transmission occurred before symptom onset of the infector. We identified six clustered outbreaks, and all were associated with indoor facilities. In 23 household contacts, the secondary attack rate was 63% (52/82). We estimated that 15% (95% confidence interval, 13–18%) of cases seeded 80% of all local transmission. Analysis of the nasopharyngeal swab samples identified virus shedding from asymptomatic patients, and the highest viral load was observed two days after symptom onset. The temporal pattern of viral shedding did not differ between children and adults (P = 0.48). Conclusions Our findings suggest that the delta variant is highly transmissible in indoor settings and households. Rapid contact tracing, isolation of the asymptomatic contacts, and strict adherence to public health measures are needed to mitigate the community transmission of the delta variant.

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