Introduction
A novel coronavirus emerged in China in late 2019. This new strain was quickly identified, and genome sequencing established that this severe acute respiratory syndrome coronavirus (SARS-CoV-2) was derived from bats [1]. On March 11, 2020, the World Health Organization (WHO) declared Coronavirus Disease 2019 (COVID-19) to be pandemic. As of July 18, 2020, SARS-CoV-2 has been responsible for more than 14000000 cases and more than 600000 deaths worldwide [2].
Incubation period is the interval time elapsed between the moment a person is infected until the onset of the disease. Knowledge of the incubation period is essential for the case definition, management of emerging threats, estimation of the duration follow-up for contact tracing and secondary case detection and the establishment of public health programs aimed at reducing local transmission [3]. Valid measurement of the incubation period might be challenging in an emergency context.
According to the WHO, SARS-CoV-2 incubation period ranging from 1 to 14 days has been reported [4]. Distribution of the incubation period may vary between individuals as a result of certain determinants such as host factors.
A paradox might be occurring; as the number of reported cases increases, the quality of the parameter increases, with a reduction of the range or the 95% confidence interval. However, the waiting time for obtaining results from large sample size delays optimal decisions for the outbreak investigation. Moreover, in case of a R0 of 2.5 to 3.0, even outliers with a long incubation period may generate secondary cases. Thus, measures of dispersion are as important as measures of central tendency. Despite the lack of knowledge regarding transmission during the incubation period, that interval conditions the amount of contacts to investigate.
The situation is evolving daily and there is an urgent need to correctly estimate the incubation period distribution of SARS-CoV-2 in order to support effective outbreak investigations in various contexts such as large or restricted geographic areas.
Therefore, the objective was to systematically review recent literature of reported summary estimates of the distribution of incubation period of SARS-CoV-2 with the aim of describing the distribution of incubation period and identifying variations through a meta-analysis.