The Incubation Period of Severe Acute Respiratory Syndrome Coronavirus 2:A Systematic Review

While the novel coronavirus continues to spread worldwide, the reported incubation period has varied between studies and is imprecise due to limited data. A literature search with certain selection criteria was conducted on May 30, 2020. In total, sixty-four articles were included, and 854 individual-level data were extracted from 30 studies for pooled analysis. Of these studies, 72% of them reported a median or mean incubation period of 4-7 days, while our estimated median was 4.9 days (95% confidence interval [CI]: 4.6-5.2). However, the inclusion of 81 asymptomatic and presymptomatic patients, as well as 31 cases with incubation periods exceeding 14 days, led to our estimation of 97.5 th percentile with 19.3 days (95% CI: 17.4-21.4), beyond the currently suggested 14-day quarantine period. Therefore, we appeal to prolong the quarantine duration, especially for areas that have insufficient testing resources, to protect susceptible populations from being infected. Article Summary LineThis article reviewed the COVID-19 studies involving incubation period and provided pooled estimation based on available data from these studies.The result showed that our estimated median incubation period is consistent with the estimates of formal studies but the 97.5 percentile is larger than ever on account of including a number of asymptomatic and presymptomatic patients.These finds suggested that we should properly prolong the isolation or quarantine period in order to identify more patients with longer incubation period and those without any symptoms.