Reduction in time delay of isolation in COVID-19 cases in South Korea

Ryu, Sukhyun; Jang, Cheolsun; Kim, Baekjin

doi:10.1101/2020.04.03.20051847

Cited by 3 publications

(3 citation statements)

References 5 publications

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“…Second, some cases may have been incorrectly attributed to the clusters while the true source of infection was elsewhere. Third, in our study, the mean reporting delay of 1.7 days, the period between symptom onset and case con rmation, was shorter than the previous estimate (mean of 3.3 days) [33]. The reduced reporting delay with rapid case isolation could shorten the serial interval by truncating the infectious period of an infector [34].…”

Section: Discussioncontrasting

confidence: 66%

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

Hwang¹,

Lim

Song³

et al. 2021

Preprint

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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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Section: Discussioncontrasting

confidence: 66%

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

Hwang¹,

Lim

Song³

et al. 2021

Preprint

Self Cite

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“…A primary case who was fully vaccinated was then imported. We assumed that the imported primary case had been isolated since their last recent exposure to the virus, while other subsequently infected individuals in the community were isolated with a default time delay of 6.8 days (estimated from the mean incubation period and the mean delay from symptom onset to isolation in South Korea 27 ). An example of the transmission events is illustrated in Fig.…”

Section: Methodsmentioning

confidence: 99%

Individual-based modeling reveals that the COVID-19 isolation period can be shortened by community vaccination

Sararat

Wangkanai

Wilasang

et al. 2022

Sci Rep

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The isolation of infected individuals and quarantine of their contacts are usually employed to mitigate the transmission of SARS-CoV-2. Although 14-day isolation of infected individuals could effectively reduce the risk of subsequent transmission, it also substantially impacts the patient's psychological and emotional well-being. It is, therefore, vital to investigate how the isolation duration could be shortened when effective vaccines are available. Here, an individual-based modeling approach was employed to estimate the likelihood of secondary infections and the likelihood of an outbreak following the isolation of a primary case for a range of isolation periods. Our individual-based model integrated the viral loads and infectiousness profiles of vaccinated and unvaccinated infected individuals. The effects of waning vaccine-induced immunity against infection were also considered. By simulating the transmission of the SARS-CoV-2 Delta (B.1.617.2) variant in a community, we found that in the baseline scenario in which all individuals were unvaccinated and nonpharmaceutical interventions were not used, there was an approximately 3% chance that an unvaccinated individual would lead to at least one secondary infection after being isolated for 14 days, and a sustained chain of transmission could occur with a less than 1% chance. With the outbreak risk equivalent to that of the 14-day isolation in the baseline scenario, we found that the isolation duration could be shortened to 7.33 days (95% CI 6.68–7.98) if 75% of people in the community were fully vaccinated with the BNT162b2 vaccine within the last three months. In the best-case scenario in which all individuals in the community are fully vaccinated, isolation of Delta variant-infected individuals may no longer be necessary. However, to keep the outbreak risk lower than 1%, a booster vaccination may be necessary three months after full vaccination.

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“…We were unable to estimate the delay to isolation of a confirmed case from the KCDC press release data. Another study, which fitted gamma distributions to case data of 211 confirmed cases, estimated the mean delay from symptom onset to isolation of cases as 4.3 days, before the red alert warning on February 23rd and 3.3 days after [74]. The same study estimated the mean delay from exposure to isolation as 7.2 days before the red alert and 6.5 days after.…”

Section: Isolationmentioning

confidence: 99%

Response to COVID-19 in South Korea and implications for lifting stringent interventions

Dighe

Cattarino

Cuomo-Dannenburg

et al. 2020

BMC Med

167

178

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Background After experiencing a sharp growth in COVID-19 cases early in the pandemic, South Korea rapidly controlled transmission while implementing less stringent national social distancing measures than countries in Europe and the USA. This has led to substantial interest in their “test, trace, isolate” strategy. However, it is important to understand the epidemiological peculiarities of South Korea’s outbreak and characterise their response before attempting to emulate these measures elsewhere. Methods We systematically extracted numbers of suspected cases tested, PCR-confirmed cases, deaths, isolated confirmed cases, and numbers of confirmed cases with an identified epidemiological link from publicly available data. We estimated the time-varying reproduction number, Rt, using an established Bayesian framework, and reviewed the package of interventions implemented by South Korea using our extracted data, plus published literature and government sources. Results We estimated that after the initial rapid growth in cases, Rt dropped below one in early April before increasing to a maximum of 1.94 (95%CrI, 1.64–2.27) in May following outbreaks in Seoul Metropolitan Region. By mid-June, Rt was back below one where it remained until the end of our study (July 13th). Despite less stringent “lockdown” measures, strong social distancing measures were implemented in high-incidence areas and studies measured a considerable national decrease in movement in late February. Testing the capacity was swiftly increased, and protocols were in place to isolate suspected and confirmed cases quickly; however, we could not estimate the delay to isolation using our data. Accounting for just 10% of cases, individual case-based contact tracing picked up a relatively minor proportion of total cases, with cluster investigations accounting for 66%. Conclusions Whilst early adoption of testing and contact tracing is likely to be important for South Korea’s successful outbreak control, other factors including regional implementation of strong social distancing measures likely also contributed. The high volume of testing and the low number of deaths suggest that South Korea experienced a small epidemic relative to other countries. Caution is needed in attempting to replicate the South Korean response in populations with larger more geographically widespread epidemics where finding, testing, and isolating cases that are linked to clusters may be more difficult.

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Reduction in time delay of isolation in COVID-19 cases in South Korea

Abstract: 25Korean public health authorities raised the public alert to its highest level on February 23, 26 2020 to mitigate the 2019 novel coronavirus disease epidemic. We have identified that the mean

Cited by 3 publications

References 5 publications

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

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

Individual-based modeling reveals that the COVID-19 isolation period can be shortened by community vaccination

Response to COVID-19 in South Korea and implications for lifting stringent interventions

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