Epidemiological Parameters of COVID-19: Case Series Study

Abstract

Background 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. Objective The 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. Methods We 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. Results In 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). Conclusions This 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.

Presymptomatic viral shedding and infective ability of SARS-CoV-2; a case report

“…This case report corroborates recent findings that presymptomatic viral shedding could be one of several factors contributing to the current SARS-CoV-2 pandemic [ 11 , 13 , 24 , 25 ]. Also, extensive viral shedding and infective potential may occur shortly after exposure to COVID-19 patients and well prior to symptoms.…”

Digital proximity tracing on empirical contact networks for pandemic control

“…While the testing and isolation of symptomatic cases is crucial, it is insufficient in the case of COVID-19, since there is clear evidence of presymptomatic and asymptomatic transmission [15][16][17][18][19] . Thus, the identification and isolation of infected cases must be coupled with a strategy for tracing their contacts and preventively quarantining them 17,[20][21][22] .…”

Epidemiology and Clinical Course of First Wave Coronavirus Disease Cases, Faroe Islands

“…The generation time is the time between infection events in a primary case and a secondary case. Generation time is difficult to observe but is expected to be approximately equal to the serial interval ( 5 , 6 ). We chose to use the serial interval in all cases in this study and we estimated the mean serial interval by using the EpiEstim package in R (R Foundation for Statistical Computing, https://www.r-project.org ).…”