Incubation period of COVID-19

Wuhan pneumonia is an acute infectious disease caused by the 2019 novel coronavirus (COVID-19). It is being treated as a Class A infectious disease though it was classified as Class B according to the Infectious Disease Prevention Act of China.

Accurate estimation of the incubation period of the coronavirus is essential for the sake of deciphering dynamics of its spread. The incubation period is the time from infection to the onset of the disease. It provides the foundation for epidemiological prevention, clinical actions, and drug discovery. Different viruses have different incubation periods that determine their different dynamics epidemiologically. The incubation period of H7N9 (Human Avian Influenza A) is about 6.5 days, but the incubation period for SARS-CoV is typically 2 to 7 days. However, it remains unclear about its exact incubation period though it is believed that symptoms of COVID-19 can appear in as few as 2 days or as long as 14 or even more after exposure. The accurate incubation period calculation requires original chain-of-infection data that may not be fully available in the Wuhan regions.

In this way, a new study is aimed to accurately calculate the incubation period of COVID-19 by taking advantage of the chain-of-infection data, which is well-documented and epidemiologically informative, outside the Wuhan regions.

Authors acquired and collected officially reported COVID-19 data from 10 regions in China except for Hubei province. To achieve the accurate calculation of the incubation period, they only involved the officially confirmed cases with a clear history of exposure and time of onset. Besides, researchers excluded those without relevant epidemiological descriptions, working or living in Wuhan for a long time, or hard to determine the possible exposure time.

The incubation period of COVID-19 did not follow general incubation distributions, and it was close to 5.0 days. That suggests that COVID-19 could have a faster distribution speed than H7N9, but the same spread speed as SARS and MERS in terms of their incubation periods. The existing spread of COVID-19 is faster than SARS partially because it has more complicate spread dynamics.

In addition, they also found that the incubation periods of the groups with age greater than 40 years and age below 40 years demonstrated a statistically significant difference. The former group had a longer incubation period and a larger variance than the latter, that is, as younger, shorter incubation period of COVID-19. Moreover, it further suggested that different quarantine time should be applied to the groups for their different incubation periods.

Finally, results further indicated that the incubation difference between males and females did not demonstrate a statistical significance, that is, gender may not be a key factor affecting the incubation period of COVID-19.

Link to the paper: https://doi.org/10.1101/2020.02.24.20027474

Editorial Disclaimer: information published during the 2020 COVID-19 pandemic may be updated frequently to reflect the dynamic nature of current understanding.

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