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      The Incubation Period of Coronavirus Disease 2019 (COVID-19) From Publicly Reported Confirmed Cases: Estimation and Application


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          A novel human coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was identified in China in December 2019. There is limited support for many of its key epidemiologic features, including the incubation period for clinical disease (coronavirus disease 2019 [COVID-19]), which has important implications for surveillance and control activities.


          To estimate the length of the incubation period of COVID-19 and describe its public health implications.


          Pooled analysis of confirmed COVID-19 cases reported between 4 January 2020 and 24 February 2020.


          News reports and press releases from 50 provinces, regions, and countries outside Wuhan, Hubei province, China.


          Persons with confirmed SARS-CoV-2 infection outside Hubei province, China.


          Patient demographic characteristics and dates and times of possible exposure, symptom onset, fever onset, and hospitalization.


          There were 181 confirmed cases with identifiable exposure and symptom onset windows to estimate the incubation period of COVID-19. The median incubation period was estimated to be 5.1 days (95% CI, 4.5 to 5.8 days), and 97.5% of those who develop symptoms will do so within 11.5 days (CI, 8.2 to 15.6 days) of infection. These estimates imply that, under conservative assumptions, 101 out of every 10 000 cases (99th percentile, 482) will develop symptoms after 14 days of active monitoring or quarantine.


          Publicly reported cases may overrepresent severe cases, the incubation period for which may differ from that of mild cases.


          This work provides additional evidence for a median incubation period for COVID-19 of approximately 5 days, similar to SARS. Our results support current proposals for the length of quarantine or active monitoring of persons potentially exposed to SARS-CoV-2, although longer monitoring periods might be justified in extreme cases.

          Primary Funding Source:

          U.S. Centers for Disease Control and Prevention, National Institute of Allergy and Infectious Diseases, National Institute of General Medical Sciences, and Alexander von Humboldt Foundation.


          Visual Abstract.

          The Incubation Period of COVID-19 From Publicly Reported Confirmed Cases

          Using news reports and press releases from provinces, regions, and countries outside Wuhan, Hubei province, China, this analysis estimates the length of the incubation period of coronavirus disease 2019 (COVID-19) and its public health implications.


          Using news reports and press releases from provinces, regions, and countries outside Wuhan, Hubei province, China, this analysis estimates the length of the incubation period of coronavirus disease 2019 (COVID-19) and its public health implications.

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          Most cited references3

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          Estimating incubation period distributions with coarse data.

          The incubation period, the time between infection and disease onset, is important in the surveillance and control of infectious diseases but is often coarsely observed. Coarse data arises because the time of infection, the time of disease onset or both are not known precisely. Accurate estimates of an incubation period distribution are useful in real-time outbreak investigations and in modeling public health interventions. We compare two methods of estimating such distributions. The first method represents the data as doubly interval-censored. The second introduces a data reduction technique that makes the computation more tractable. In a simulation study, the methods perform similarly when estimating the median, but the first method yields more reliable estimates of the distributional tails. We conduct a sensitivity analysis of the two methods to violations of model assumption and we apply these methods to historical incubation period data on influenza A and respiratory syncytial virus. The analysis of reduced data is less computationally intensive and performs well for estimating the median under a wide range of conditions. However for estimation of the tails of the distribution, the doubly interval-censored analysis is the recommended procedure. (c) 2009 John Wiley & Sons, Ltd.
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            Comparison of incubation period distribution of human infections with MERS-CoV in South Korea and Saudi Arabia

            The incubation period is an important epidemiologic distribution, it is often incorporated in case definitions, used to determine appropriate quarantine periods, and is an input to mathematical modeling studies. Middle East Respiratory Syndrome coronavirus (MERS) is an emerging infectious disease in the Arabian Peninsula. There was a large outbreak of MERS in South Korea in 2015. We examined the incubation period distribution of MERS coronavirus infection for cases in South Korea and in Saudi Arabia. Using parametric and nonparametric methods, we estimated a mean incubation period of 6.9 days (95% credibility interval: 6.3–7.5) for cases in South Korea and 5.0 days (95% credibility interval: 4.0–6.6) among cases in Saudi Arabia. In a log-linear regression model, the mean incubation period was 1.42 times longer (95% credibility interval: 1.18–1.71) among cases in South Korea compared to Saudi Arabia. The variation that we identified in the incubation period distribution between locations could be associated with differences in ascertainment or reporting of exposure dates and illness onset dates, differences in the source or mode of infection, or environmental differences.
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              Is Open Access

              Quantifying the Risk and Cost of Active Monitoring for Infectious Diseases

              During outbreaks of deadly emerging pathogens (e.g., Ebola, MERS-CoV) and bioterror threats (e.g., smallpox), actively monitoring potentially infected individuals aims to limit disease transmission and morbidity. Guidance issued by CDC on active monitoring was a cornerstone of its response to the West Africa Ebola outbreak. There are limited data on how to balance the costs and performance of this important public health activity. We present a framework that estimates the risks and costs of specific durations of active monitoring for pathogens of significant public health concern. We analyze data from New York City’s Ebola active monitoring program over a 16-month period in 2014–2016. For monitored individuals, we identified unique durations of active monitoring that minimize expected costs for those at “low (but not zero) risk” and “some or high risk”: 21 and 31 days, respectively. Extending our analysis to smallpox and MERS-CoV, we found that the optimal length of active monitoring relative to the median incubation period was reduced compared to Ebola due to less variable incubation periods. Active monitoring can save lives but is expensive. Resources can be most effectively allocated by using exposure-risk categories to modify the duration or intensity of active monitoring.

                Author and article information

                Ann Intern Med
                Ann. Intern. Med
                Annals of Internal Medicine
                American College of Physicians
                10 March 2020
                [1 ]Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland (S.A.L., K.H.G., Q.B., F.K.J., Q.Z., H.R.M., A.S.A., J.L.)
                [2 ]School of Public Health and Health Sciences, University of Massachusetts, Amherst, Massachusetts, and Ludwig-Maximilians-Universität, Munich, Germany (N.G.R.)

                This article is made available via the PMC Open Access Subset for unrestricted re-use for research, analyses, and text and data mining through PubMed Central. Acknowledgement of the original source shall include a notice similar to the following: “© 2020 American College of Physicians. Some rights reserved. This work permits non-commercial use, distribution, and reproduction in any medium, provided the original author and source are credited.” These permissions are granted for the duration of the COVID-19 pandemic or until permissions are revoked in writing. Upon expiration of these permissions, PMC is granted a perpetual license to make this article available via PMC and Europe PMC, consistent with existing copyright protections.

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                Hospital Medicine


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