Transmission of COVID-19 in the terminal stage of incubation period: a familial cluster.

•We report a familial cluster of COVID-19 to assess potential transmission of the disease during the incubation period.•A familial cluster of four patients with COVID-19 in Zhoushan, China had contact with an asymptomatic family member, who developed symptoms later.•The infectivity during the incubation period for SARS-CoV-2 is a big challenge for controlling the disease.