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From a total of 71 laboratory-confirmed cases, three presymptomatic patients and 10 patients with entirely asymptomatic infections were identified. In two of the three incubation period patients, the viral titer in the presymptomatic period was very high (Ct value < 20). The median number of days to first negative RT-PCR in the asymptomatic carriers was 4.5 (range 2.5–9), and all asymptomatic carriers reached a first RT-PCR Ct > 35 within 14 days after diagnosis. Patients who have COVID-19 may already be infectious before there are symptoms, and 14 days of isolation after diagnosis may be sufficient in entirely asymptomatic cases.