Cases of 2019-nCoV nucleic acid and antibody (IgM and IgG total antibody) after discharge from a hospital in Chongqing were continuously monitored. It was found that 5 cases of "re-positive" phenomenon, 5 cases of antibody were positive, and there was a trend of increasing with time. "Re-Positive" may be related to the following three factors. Children with asymptomatic infection had a long time of fecal detoxification.There were two consecutive nucleic acid tests "false negative" caused by various reasons.The virus clearance in patients was not complete, and the discharge standard was not conservative enough. The analysis of the causes of "Re-Positive" patients and the discussion of its infection will help us reveal more characteristics of this virus, and to provide a new basis for the discharge standard in the constantly updated diagnosis and treatment programme.

Objective: To understand the possible transmission route of a family cluster of COVID-19 in Zhengzhou and the potential infectivity of COVID-19 in incubation period, and provide scientific evidence for the timely control of infectious source and curb the spread of the epidemic. Methods: Epidemiological investigation was conducted for a family cluster of COVID-19 (8 cases) with descriptive epidemiological method, and respiratory tract samples of the cases were collected for the nucleic acid detection of 2019-nCoV by RT-PCR. Results: Two primary cases, which occurred on 31 January and 1 February, 2020, respectively, had a common exposure history in Wuhan. The other six family members had onsets on 30 January, 31 January, 1 February (three cases) and 3 February, 2020. Conclusions In this family cluster of COVID-19, six family members were infected through common family exposure to the 2 primary cases. Five secondary cases had onsets earlier than or on the same day as the primary cases, indicating that COVID-19 is contagious in incubation period, and the home isolation in the early phase of the epidemic might lead to the risk of family cluster of COVID-19.