All Summaries of Evidence: 12 March 2020 What is the incubation period for COVID-19?

What is the incubation period for COVID-19?

BMJ Best Practice

COVID-19: Aetiology and Pathophysiology Current estimates of the incubation period range from 1 to 14 days, according to the World Health Organization1 and the US Centers for Disease Control and Prevention. 2 The median incubation period has been estimated to be 5 days. 3 Transmission may be possible during the incubation period. ⁴

Primary Research

Laueret al. Incubation Periodof Coronavirus Disease 2019from Publicly Reported Confirmed Cases: Estimation and Application⁵

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 over-represent 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.

Linton et al. Incubation Period and Other Epidemiological Characteristics of 2019 Novel Coronavirus Infections⁶

Abstract: The geographic spread of 2019 novel coronavirus (COVID-19) infections from the epicentre of Wuhan, China, has provided an opportunity to study the natural history of the recently emerged virus. Using publicly available eventdate 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. Backeret al. Incubation Period of 2019 Novel Coronavirus(2019-nCoV) Infections among Travellers from Wuhan, China7 Using the travel history and symptom onset of 88 confirmed cases that were detected outside Wuhan in the early outbreak phase, we estimate the mean incubation period to be 6.4 days (95% credible interval: 5.6-7.7), ranging from 2.1 to 11.1 days (2.5th to 97.5th percentile). These values should help inform 2019-nCoV case definitions and appropriate quarantine durations.

PICOT

Authors

Brendan Leen, Regional Librarian, HSE South, St. Luke’s General Hospital, Kilkenny; Gethin White, Librarian, Dr. Steevens’ Hospital, Dublin; Isabelle Delaunois, Librarian, University Hospital Limerick; Linda Halton, Librarian, Our Lady’s Hospital, Navan; Marie Carrigan, Librarian, St. Luke’s Radiation Oncology Network, Dublin; Pauline Ryan, Librarian, University Hospital Waterford; Ronan Hegarty, Librarian, Naas General Hospital; Bennery Rickard, Regional Librarian, Dr. Steevens’ Hospital, Dublin.

References

1. World Health Organization. Novel coronavirus (2019-nCoV) situation report - 6. January 2020 [internet publication]. https://www.who.int/docs/defaultsource/coronaviruse/situation-reports/20200126-sitrep-6-2019--ncov.pdf
2. Centers for Disease Control and Prevention. Coronavirus disease 2019 (COVID-19): symptoms. February 2020 [internet publication]. https://www.cdc.gov/coronavirus/2019-ncov/about/symptoms.html
3. https://www.ncbi.nlm.nih.gov/pubmed/31995857
4. https://www.ncbi.nlm.nih.gov/pubmed/32067043
5. https://www.ncbi.nlm.nih.gov/pubmed/32150748.
6. https://www.ncbi.nlm.nih.gov/pubmed/32079150.
7. https://www.ncbi.nlm.nih.gov/pubmed/32046819