The incubation period for COVID-19 can range from 2 to 14 days. The incubation period can vary greatly among patients. There is a possible outlier of a 24 days incubation period that was observed in a Feb 9, 2020 study.
Summary of findings:
- Based on a study of 88 people who came down with COVID-19 after they left Wuhan China the mean incubation period was calculated 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). Source: “Incubation period of 2019 novel coronavirus (2019-nCoV) infections among travelers from Wuhan, China, between the 20th and 28th of January 2020. Published by the NIH on Feb 6, 2020.
- An outlier of a 24 days incubation period was reported in a Feb. 9 study. In a press conference WHO said this could reflect a second exposure rather than a longer incubation and quarantine recommendation. However, WHO did not change their official estimated range for the novel coronavirus COVID-19 incubation period from 2 to 14 days.
- Reuters reported on Feb 21, 2020, that a 70-year-old man in China’s Hubei Province had an incubation period of 24 days according to a local government report on Feb. 22, 2020.
- A case with an incubation period of 19 days was observed in a JAMA (Journal of the American Medical Association) study of 5 cases published on Feb. 21.
- Mean incubation period observed:
- In a study published Feb 9, 2020, in a pre-peer-reviewed article in medRxiv, a mean incubation period of 3.0 days was observed (0 – 24 days range, a study based on 1,324 cases
- A Chinese study published in the New England Journal of Medicine on Jan. 29, 2020, found the incubation period to be 5.2 days on average for 425 people studied, but it varies greatly among patients.
- The CDC on April 3, 2020, published that the incubation period for COVID-19 is thought to extend to 14 days, with a median time of 4-5 days from exposure to symptoms onset. CDC referenced one study that reported that 97.5% of persons with COVID-19 who develop symptoms will do so within 11.5 days of SARS-CoV-2 infection.
I will continue to update this summary as new information becomes available.