- However, a case with an incubation period of 27 days has been reported by Hubei Province local government on Feb. 22.
- In addition, a case with an incubation period of 19 days was observed in a JAMA study of 5 cases published on Feb. 21.
- An outlier of a 24 days incubation period had been for the first time observed in a Feb. 9 study. WHO said at the time that this could actually reflect a second exposure rather than a long incubation period and that it wasn't going to change its recommendation.
- The period can vary greatly among patients.
- Mean incubation period observed:
5.2 days (4.1 - 7.0 days range, based on 425 cases).
The incubation period (time from exposure to the development of symptoms) of the virus is estimated to be between 2 and 14 days based on the following sources:
- The World Health Organization (WHO) reported an incubation period for COVID-19 between 2 and 10 days.
- China’s National Health Commission (NHC) had initially estimated an incubation period from 10 to 14 days.
- The United States' CDC estimates the incubation period for COVID-19 to be between 2 and 14 days.
- DXY.cn, a leading Chinese online community for physicians and health care professionals, is reporting an incubation period of "3 to 7 days, up to 14 days".
The estimated range will be most likely narrowed down as more data becomes available.
The incubation period has been found to be as long as 24 days (range: 0-24 days; median: 3.0 days) in a study published on February 9.
- a very long incubation period could reflect a double exposure.
- 24 days represented an outlier observation that must be taken into consideration in the context of the main finding of the study.
- WHO is not considering changing recommendations regarding incubation periods.
The incubation period of 5.2 days on average
A study financed by the Netherlands Ministry of Health and published on Eurosurveillance, analyzed data on 88 cases with known travel history (to and) from Wuhan which were detected between 20 and 28 January as being infected with COVID-19.
The mean incubation period was estimated to be 6.4 days. The incubation period ranges from 2.1 to 11.1 days. The upper limit of 11.1 days could be considered conservative.
For comparison, the incubation period for the common flu (seasonal influenza) is typically around 2 days. The incubation period for other coronaviruses: SARS 2-7 days; MERS 5 days typically (range 2-14 days).