Abstract
BackgroundThe estimates of several key epidemiological parameters of the COVID-19 pandemic are often based on small sample sizes or are inaccurate for various reasons.ObjectiveThe aim of this study is to obtain more robust estimates of the incubation period, serial interval, frequency of presymptomatic transmission, and basic reproduction number (R0) of COVID-19 based on a large case series.MethodsWe systematically retrieved and screened 20,658 reports of laboratory-confirmed COVID-19 cases released by the health authorities of China, Japan, and Singapore. In addition, 9942 publications were retrieved from PubMed and China National Knowledge Infrastructure (CNKI) through April 8, 2020. To be eligible, a report had to contain individual data that allowed for accurate estimation of at least one parameter. Widely used models such as gamma distributions were fitted to the data sets and the results with the best-fitting values were presented.ResultsIn total, 1591 cases were included for the final analysis. The mean incubation period (n=687) and mean serial interval (n=1015 pairs) were estimated to be 7.04 (SD 4.27) days and 6.49 (SD 4.90) days, respectively. In 40 cases (5.82%), the incubation period was longer than 14 days. In 32 infector-infectee pairs (3.15%), infectees’ symptom onsets occurred before those of infectors. Presymptomatic transmission occurred in 129 of 296 infector-infectee pairs (43.58%). R0 was estimated to be 1.85 (95% CI 1.37-2.60).ConclusionsThis study provides robust estimates of several epidemiological parameters of COVID-19. The findings support the current practice of 14-day quarantine of persons with potential exposure, but also suggest the need for additional measures. Presymptomatic transmission together with the asymptomatic transmission reported by previous studies highlight the importance of adequate testing, strict quarantine, and social distancing.
Highlights
In December 2019, a novel enveloped ribonucleic acid (RNA) beta-coronavirus, which was later named SARS-CoV-2, was first reported in Wuhan, the capital city of Hubei province, China [1]
This study provides robust estimates of several epidemiological parameters of COVID-19
COVID-19, the disease caused by SARS-CoV-2, spread across and outside China rapidly, and was declared a pandemic by the World Health Organization on March 11, 2020
Summary
In December 2019, a novel enveloped ribonucleic acid (RNA) beta-coronavirus, which was later named SARS-CoV-2, was first reported in Wuhan, the capital city of Hubei province, China [1]. 1 (page number not for citation purposes) the disease remain to be clarified, among which are incubation period and serial interval. The mean or median incubation period and serial interval estimated by previous studies were mostly 4-5 days [5,6,7,8,9,10,11,12,13,14,15,16]. In a study by Zhang et al [16], which included 8579 cases, only 49 cases and 39 pairs could be used for estimating incubation period and serial interval, respectively. The estimates of several key epidemiological parameters of the COVID-19 pandemic are often based on small sample sizes or are inaccurate for various reasons
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