Clinical Characteristics of 24 Asymptomatic Infections with COVID 19 Screened among Close Contacts in Nanjing, China
Background: Previous studies have showed clinical characteristics of patients with the 2019 novel coronavirus disease (COVID 19) and the evidence of person to person transmission. Limited data are available for asymptomatic infections. This study aims to present the clinical characteristics of 24 cases with asymptomatic infection screened from close contacts and to show the transmission potential of asymptomatic COVID 19 virus carriers. Methods: Epidemiological investigations were conducted among all close contacts of COVID 19 patients (or suspected patients) in Nanjing, Jiangsu Province, China, from Jan 28 to Feb 9, 2020, both in clinic and in community. Asymptomatic carriers were laboratory confirmed positive for the COVID 19 virus by testing the nucleic acid of the pharyngeal swab samples. Their clinical records, laboratory assessments, and chest CT scans were reviewed. Findings: None of the 24 asymptomatic cases presented any obvious symptoms before nucleic acid screening. Five cases (20.8% developed symptoms (fever, cough, fatigue and etc. during hospitalization. Twelve (50.0% cases showed typical CT images of ground glass chest and five (20.8% presented stripe shadowing in the lungs. The remaining seven (29.2% cases showed normal CT image and had no symptoms during hospitalization. These seven cases were younger (median age: 14.0 years; P 0.012) than the rest. None of the 24 cases developed severe COVID 19 pneumonia or died. The median communicable period, defined as the interval from the first day of positive nucleic acid tests to the first day of continuous negative tests, was 9.5 days (up to 21 days among the 24 asymptomatic cases) Through epidemiological investigation, we observed a typical asymptomatic transmission to the cohabiting family members, which even caused severe COVID 19 pneumonia. Interpretation: The asymptomatic carriers identified from close contacts were prone to be mildly ill during hospitalization. However, the communicable period could be up to three weeks and the communicated patients could develop severe illness. These results highlighted the importance of close contact tracing and longitudinally surveillance via virus nucleic acid tests. Further isolation recommendation and continuous nucleic acid tests may also be recommended to the patients discharged.
medRxiv