Serial interval of novel coronavirus (COVID-19) infections.
TL;DR: The serial interval of COVID-19 is close to or shorter than its median incubation period, indicating that a substantial proportion of secondary transmission may occur prior to illness onset and that calculations made using the SARS serial interval may introduce bias.
About: This article is published in International Journal of Infectious Diseases.The article was published on 2020-03-04 and is currently open access. It has received 963 citations till now. The article focuses on the topics: Serial interval & Credible interval.
Citations
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Xi He1, Eric H. Y. Lau2, Peng Wu2, Xilong Deng1, Jian Wang1, Xinxin Hao2, Yiu Chung Lau2, Jessica Y. Wong2, Yujuan Guan1, Xinghua Tan1, Xiaoneng Mo1, Yanqing Chen1, Baolin Liao1, Weilie Chen1, Fengyu Hu1, Qing Zhang1, Mingqiu Zhong1, Yanrong Wu1, Lingzhai Zhao1, Fuchun Zhang1, Benjamin J. Cowling2, Fang Li1, Gabriel M. Leung2 •
TL;DR: It is estimated that 44% (95% confidence interval, 25–69%) of secondary cases were infected during the index cases’ presymptomatic stage, in settings with substantial household clustering, active case finding and quarantine outside the home.
Abstract: We report temporal patterns of viral shedding in 94 patients with laboratory-confirmed COVID-19 and modeled COVID-19 infectiousness profiles from a separate sample of 77 infector–infectee transmission pairs. We observed the highest viral load in throat swabs at the time of symptom onset, and inferred that infectiousness peaked on or before symptom onset. We estimated that 44% (95% confidence interval, 30–57%) of secondary cases were infected during the index cases’ presymptomatic stage, in settings with substantial household clustering, active case finding and quarantine outside the home. Disease control measures should be adjusted to account for probable substantial presymptomatic transmission. Presymptomatic transmission of SARS-CoV-2 is estimated to account for a substantial proportion of COVID-19 cases.
3,943 citations
Nicholas G Davies1, Sam Abbott1, Rosanna C. Barnard1, Christopher I Jarvis1, Adam J. Kucharski1, James D Munday1, Carl A. B. Pearson1, Timothy W Russell1, Damien C. Tully1, Alex D. Washburne, Tom Wenseleers2, Amy Gimma1, William Waites1, Kerry L. M. Wong1, Kevin van Zandvoort1, Justin D. Silverman3, Karla Diaz-Ordaz1, Ruth H. Keogh1, Rosalind M Eggo1, Sebastian Funk1, Mark Jit1, Katherine E. Atkins1, Katherine E. Atkins4, W. John Edmunds1 •
TL;DR: Using a variety of statistical and dynamic modeling approaches, the authors estimate that this variant has a 43 to 90% (range of 95% credible intervals, 38 to 130%) higher reproduction number than preexisting variants, and a fitted two-strain dynamic transmission model shows that VOC 202012/01 will lead to large resurgences of COVID-19 cases.
Abstract: A severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant, VOC 202012/01 (lineage B.1.1.7), emerged in southeast England in September 2020 and is rapidly spreading toward fixation. Using a variety of statistical and dynamic modeling approaches, we estimate that this variant has a 43 to 90% (range of 95% credible intervals, 38 to 130%) higher reproduction number than preexisting variants. A fitted two-strain dynamic transmission model shows that VOC 202012/01 will lead to large resurgences of COVID-19 cases. Without stringent control measures, including limited closure of educational institutions and a greatly accelerated vaccine rollout, COVID-19 hospitalizations and deaths across England in the first 6 months of 2021 were projected to exceed those in 2020. VOC 202012/01 has spread globally and exhibits a similar transmission increase (59 to 74%) in Denmark, Switzerland, and the United States.
1,935 citations
TL;DR: In this paper, the authors proposed a new model that predicts the course of the SARS-CoV-2 pandemic to help plan an effective control strategy, including social distancing, testing and contact tracing.
Abstract: In Italy, 128,948 confirmed cases and 15,887 deaths of people who tested positive for SARS-CoV-2 were registered as of 5 April 2020. Ending the global SARS-CoV-2 pandemic requires implementation of multiple population-wide strategies, including social distancing, testing and contact tracing. We propose a new model that predicts the course of the epidemic to help plan an effective control strategy. The model considers eight stages of infection: susceptible (S), infected (I), diagnosed (D), ailing (A), recognized (R), threatened (T), healed (H) and extinct (E), collectively termed SIDARTHE. Our SIDARTHE model discriminates between infected individuals depending on whether they have been diagnosed and on the severity of their symptoms. The distinction between diagnosed and non-diagnosed individuals is important because the former are typically isolated and hence less likely to spread the infection. This delineation also helps to explain misperceptions of the case fatality rate and of the epidemic spread. We compare simulation results with real data on the COVID-19 epidemic in Italy, and we model possible scenarios of implementation of countermeasures. Our results demonstrate that restrictive social-distancing measures will need to be combined with widespread testing and contact tracing to end the ongoing COVID-19 pandemic.
1,432 citations
TL;DR: A significantly decreased growth rate and increased doubling time of cases was observed, which is most likely due to Chinese lockdown measures, which seem to have a potential to slow down the spread of COVID-19.
Abstract: BACKGROUND With its epicenter in Wuhan, China, the COVID-19 outbreak was declared a Public Health Emergency of International Concern by the World Health Organization (WHO). Consequently, many countries have implemented flight restrictions to China. China itself has imposed a lockdown of the population of Wuhan as well as the entire Hubei province. However, whether these two enormous measures have led to significant changes in the spread of COVID-19 cases remains unclear. METHODS We analyzed the available data on the development of confirmed domestic and international COVID-19 cases before and after lockdown measures. We evaluated the correlation of domestic air traffic to the number of confirmed COVID-19 cases and determined the growth curves of COVID-19 cases within China before and after lockdown as well as after changes in COVID-19 diagnostic criteria. RESULTS Our findings indicate a significant increase in doubling time from 2 days (95% CI: 1.9-2.6) to 4 days (95% CI: 3.5-4.3), after imposing lockdown. A further increase is detected after changing diagnostic and testing methodology to 19.3 (95% CI: 15.1-26.3), respectively. Moreover, the correlation between domestic air traffic and COVID-19 spread became weaker following lockdown (before lockdown: r = 0.98, P < 0.05 vs after lockdown: r = 0.91, P = NS). CONCLUSIONS A significantly decreased growth rate and increased doubling time of cases was observed, which is most likely due to Chinese lockdown measures. A more stringent confinement of people in high risk areas seems to have a potential to slow down the spread of COVID-19.
982 citations
TL;DR: Although a number of assumptions need to be reexamined, like age structure in social mixing patterns and in the distribution of mobility, hospitalization, and fatality, it is concluded that verifiable evidence exists to support the planning of emergency measures.
Abstract: The spread of coronavirus disease 2019 (COVID-19) in Italy prompted drastic measures for transmission containment. We examine the effects of these interventions, based on modeling of the unfolding epidemic. We test modeling options of the spatially explicit type, suggested by the wave of infections spreading from the initial foci to the rest of Italy. We estimate parameters of a metacommunity Susceptible-Exposed-Infected-Recovered (SEIR)-like transmission model that includes a network of 107 provinces connected by mobility at high resolution, and the critical contribution of presymptomatic and asymptomatic transmission. We estimate a generalized reproduction number ([Formula: see text] = 3.60 [3.49 to 3.84]), the spectral radius of a suitable next-generation matrix that measures the potential spread in the absence of containment interventions. The model includes the implementation of progressive restrictions after the first case confirmed in Italy (February 21, 2020) and runs until March 25, 2020. We account for uncertainty in epidemiological reporting, and time dependence of human mobility matrices and awareness-dependent exposure probabilities. We draw scenarios of different containment measures and their impact. Results suggest that the sequence of restrictions posed to mobility and human-to-human interactions have reduced transmission by 45% (42 to 49%). Averted hospitalizations are measured by running scenarios obtained by selectively relaxing the imposed restrictions and total about 200,000 individuals (as of March 25, 2020). Although a number of assumptions need to be reexamined, like age structure in social mixing patterns and in the distribution of mobility, hospitalization, and fatality, we conclude that verifiable evidence exists to support the planning of emergency measures.
948 citations
References
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Qun Li1, Xuhua Guan1, Peng Wu2, Xiaoye Wang1, Lei Zhou1, Yeqing Tong1, Ruiqi Ren1, Kathy Leung2, Eric H. Y. Lau2, Jessica Y. Wong2, Xuesen Xing1, Nijuan Xiang1, Yang Wu1, Chao Li1, Chen Qi1, Dan Li1, Tian Liu1, Jing Zhao1, Man Liu1, Wenxiao Tu1, Chuding Chen1, Lianmei Jin1, Rui Yang1, Qi Wang1, Suhua Zhou1, Rui Wang1, Hui Liu1, Yingbo Luo1, Yuan Liu1, Ge Shao1, Huan Li1, Zhongfa Tao1, Yang Yang3, Yang Yang4, Zhiqiang Deng5, Boxi Liu5, Zhitao Ma5, Yanping Zhang1, Guoqing Shi1, Tommy Tsan-Yuk Lam2, Joseph T. Wu2, George F. Gao1, George F. Gao6, Benjamin J. Cowling2, Bo Yang5, Gabriel M. Leung2, Zijian Feng1 •
TL;DR: There is evidence that human-to-human transmission has occurred among close contacts since the middle of December 2019 and considerable efforts to reduce transmission will be required to control outbreaks if similar dynamics apply elsewhere.
Abstract: Background The initial cases of novel coronavirus (2019-nCoV)–infected pneumonia (NCIP) occurred in Wuhan, Hubei Province, China, in December 2019 and January 2020. We analyzed data on the...
13,101 citations
TL;DR: Investigators in Germany detected the spread of the novel coronavirus (2019-nCoV) from a person who had recently traveled from China and found it to be a novel virus.
Abstract: 2019-nCoV Transmission from Asymptomatic Patient In this report, investigators in Germany detected the spread of the novel coronavirus (2019-nCoV) from a person who had recently traveled from China...
3,492 citations
"Serial interval of novel coronaviru..." refers background or methods in this paper
...Pairs of cases that cannot be scientifically linked were classified as “uncertain” and removed from our analysis, and the verification of illness onset date was ensured following an erratum report of presymptomatic transmissions in Germany [4]....
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...First, our data include the updated information from a recent report of pre-symptomatic transmission in Germany [4] where it was later found that the primary case was already symptomatic while in contact with persons who later became infected...
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...First, our data include the updated information from a recent report of pre-symptomatic transmission in Germany [4] where it was later found that the primary case was already symptomatic while in contact with persons who later became infected (Supplementary Material in [4])....
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TL;DR: It is estimated that a single infectious case of SARS will infect about three secondary cases in a population that has not yet instituted control measures, and public-health efforts to reduce transmission are expected to have a substantial impact on reducing the size of the epidemic.
Abstract: Severe acute respiratory syndrome (SARS) is a recently described illness of humans that has spread widely over the past 6 months. With the use of detailed epidemiologic data from Singapore and epidemic curves from other settings, we estimated the reproductive number for SARS in the absence of interventions and in the presence of control efforts. We estimate that a single infectious case of SARS will infect about three secondary cases in a population that has not yet instituted control measures. Public-health efforts to reduce transmission are expected to have a substantial impact on reducing the size of the epidemic.
1,409 citations
"Serial interval of novel coronaviru..." refers background or methods in this paper
...4-day mean serial interval reported for severe acute respiratory syndrome (SARS) from Singaporean household contact data [3]....
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...Figure 1 shows the best-fit distributions overlaid with a published distribution of the SARS serial interval [3]....
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TL;DR: The incubation period falls within the range of 2–14 days with 95% confidence and has a mean of around 5 days when approximated using the best-fit lognormal distribution and it is recommended that the length of quarantine should be at least 14 days.
Abstract: The geographic spread of 2019 novel coronavirus (COVID-19) infections from the epicenter of Wuhan, China, has provided an opportunity to study the natural history of the recently emerged virus. Using publicly available event-date data from the ongoing epidemic, the present study investigated the incubation period and other time intervals that govern the epidemiological dynamics of COVID-19 infections. Our results show that the incubation period falls within the range of 2–14 days with 95% confidence and has a mean of around 5 days when approximated using the best-fit lognormal distribution. The mean time from illness onset to hospital admission (for treatment and/or isolation) was estimated at 3–4 days without truncation and at 5–9 days when right truncated. Based on the 95th percentile estimate of the incubation period, we recommend that the length of quarantine should be at least 14 days. The median time delay of 13 days from illness onset to death (17 days with right truncation) should be considered when estimating the COVID-19 case fatality risk.
1,222 citations
TL;DR: It is concluded that severe acute respiratory syndrome and smallpox are easier to control using these simple public health measures and should be a priority during an outbreak of a novel infectious agent.
Abstract: The aim of this study is to identify general properties of emerging infectious agents that determine the likely success of two simple public health measures in controlling outbreaks, namely (i) isolating symptomatic individuals and (ii) tracing and quarantining their contacts. Because these measures depend on the recognition of specific disease symptoms, we investigate the relative timing of infectiousness and the appearance of symptoms by using a mathematical model. We show that the success of these control measures is determined as much by the proportion of transmission occurring prior to the onset of overt clinical symptoms (or via asymptomatic infection) as the inherent transmissibility of the etiological agent (measured by the reproductive number R0). From published studies, we estimate these quantities for two moderately transmissible viruses, severe acute respiratory syndrome coronavirus and HIV, and for two highly transmissible viruses, smallpox and pandemic influenza. We conclude that severe acute respiratory syndrome and smallpox are easier to control using these simple public health measures. Direct estimation of the proportion of asymptomatic and presymptomatic infections is achievable by contact tracing and should be a priority during an outbreak of a novel infectious agent.
1,093 citations
"Serial interval of novel coronaviru..." refers background in this paper
...A substantial proportion of secondary transmission occurring before illness onset indicates that many transmissions cannot be prevented solely through isolation of symptomatic cases, as by the time contacts are traced they may have already become infectious themselves and generated secondary cases [9]....
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The serial interval of COVID-19 is close to or shorter than its median incubation period.