Asymptomatic patients and asymptomatic phases of Coronavirus Disease 2019 (COVID-19): a population-based surveillance study

In this population-based study, we identified 307 confirmed COVID-19 cases from massive surveillance, including 129,551 individuals screened at fever clinics or returning from Hubei and 3710 close contacts of confirmed COVID-19 patients Among them, 17 patients were asymptomatic at initial clinical assessment These asymptomatic patients on admission accounted for a small proportion of all patients (5 54%) with relatively weak transmissibility, and the detection rate was 0 35 per 100 close contacts Moreover, the dynamics of symptoms of the 307 patients showed that the interval from symptom remission to the final negativity of viral nucleic acid was 5 0 days (IQR 2 0 to 11 0 days), with 14 patients (4 56%) having re-detectable viral RNA after discharge Together, our findings suggested asymptomatic carriers and presymptomatic patients only accounted for a small proportion of COVID-19 Also, the asymptomatic phase in during recovery of COVID-19 urged that negativity in viral RNA is necessary as de-isolation criteria and follow-up is recommended