AUTHOR=Li Menghui , Liu Kai , Song Yukun , Wang Ming , Wu Jinshan 

TITLE=Serial Interval and Generation Interval for Imported and Local Infectors, Respectively, Estimated Using Reported Contact-Tracing Data of COVID-19 in China

JOURNAL=Frontiers in Public Health

VOLUME=Volume 8 - 2020

YEAR=2021

URL=https://www.frontiersin.org/journals/public-health/articles/10.3389/fpubh.2020.577431

DOI=10.3389/fpubh.2020.577431

ISSN=2296-2565

ABSTRACT=The emerging virus, COVID-19, has caused a massive outbreak worldwide. Based on the publicly available contact-tracing data, we identified $509$ transmission chains from $20$ provinces in China and estimated the serial interval (SI) and generation interval (GI) of COVID-19 in China. Inspired by possibly different values of the time-varying reproduction number for the imported cases and the local cases in China, we divided all transmission events into three subsets: imported (the zeroth generation) infecting 1st-generation locals, 1st-generation locals infecting 2nd-generation locals, and others transmissions among $2+$. The corresponding SI (GI) is respectively denoted as $\mbox{SI}^{0}_{1}$($\mbox{GI}^{0}_{1}$), $\mbox{SI}^{1}_{2}$ ($\mbox{GI}^{1}_{2}$), and $\mbox{SI}^{2+}_{3+}$($\mbox{GI}^{2+}_{3+}$). A Bayesian approach with doubly interval-censored likelihood is employed to fit the distribution function of the SI and GI. It is found that the estimated 
$\mbox{SI}^{0}_{1}=6.52\left(95\%\mbox{CI}:  5.96-7.13\right)$, 
$\mbox{SI}^{1}_{2}=6.01\left(95\%\mbox{CI}: 5.44-6.64\right)$, $\mbox{SI}^{2+}_{3+}=4.39\left(95\%\mbox{CI}: 3.74-5.15\right)$, and $\mbox{GI}^{0}_{1}=5.47\left(95\%\mbox{CI}: 4.57-6.45\right)$, 
$\mbox{GI}^{1}_{2}=5.01\left(95\%\mbox{CI}: 3.58-7.06\right)$,
$\mbox{GI}^{2+}_{3+}=4.25 \left(95\%\mbox{CI}: 2.82-6.23\right)$. Thus overall both SI and GI decrease when generation increases.