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The Incubation Period of Coronavirus Disease 2019 (COVID-19) From Publicly Reported Confirmed Cases: Estimation and
Stephen A Lauer1, Kyra H Grantz1, Qifang Bi1
1Johns 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.).
Insights
The median incubation period for coronavirus disease 2019 (COVID-19) is approximately 5 days. This finding supports current quarantine guidelines but suggests longer monitoring may be needed for some severe cases.
Area of Science:
- Epidemiology
- Infectious Diseases
- Public Health
Background:
- Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in late 2019, necessitating understanding of its incubation period.
- Accurate incubation period data is crucial for effective COVID-19 surveillance and control strategies.
Purpose of the Study:
- To estimate the incubation period of coronavirus disease 2019 (COVID-19).
- To analyze the public health implications of the COVID-19 incubation period.
Main Methods:
- Pooled analysis of 181 confirmed COVID-19 cases reported between January 4 and February 24, 2020.
- Data sourced from news reports and press releases outside of Wuhan, China.
- Inclusion of patient demographics, exposure, symptom onset, and hospitalization data.
Main Results:
- The median incubation period for COVID-19 was estimated at 5.1 days (95% CI, 4.5–5.8).
- 97.5% of symptomatic individuals developed symptoms within 11.5 days (CI, 8.2–15.6) of infection.
- Under conservative assumptions, approximately 101 per 10,000 cases may develop symptoms after 14 days.
Conclusions:
- Findings provide evidence for a median COVID-19 incubation period of approximately 5 days, similar to SARS.
- Results support current quarantine and active monitoring durations for potential SARS-CoV-2 exposure.
- Longer monitoring periods may be warranted for certain severe cases.
Background:
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.
Objective:
To estimate the length of the incubation period of COVID-19 and describe its public health implications.
Design:
Pooled analysis of confirmed COVID-19 cases reported between 4 January 2020 and 24 February 2020.
Setting:
News reports and press releases from 50 provinces, regions, and countries outside Wuhan, Hubei province, China.
Participants:
Persons with confirmed SARS-CoV-2 infection outside Hubei province, China.
Measurements:
Patient demographic characteristics and dates and times of possible exposure, symptom onset, fever onset, and hospitalization.
Results:
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.
Limitation:
Publicly reported cases may overrepresent severe cases, the incubation period for which may differ from that of mild cases.
Conclusion:
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.
