A Cohort of SARS-CoV-2 Infected Asymptomatic and Pre-Symptomatic Contacts from COVID-19 Contact Tracing in Hubei Province, China: Short-Term Outcomes (preprint)

ABSTRACT

Background: Contact tracing with quarantine of SARS-CoV-2 positive contacts is required on an unprecedented scale worldwide.Methods: During February 1-March 25, 2020, COVID-19 cases in Hubei province were traced by more than 1800 teams. PCR positive contacts without COVID-19 symptoms with two or more consecutive positive tests for SARS-CoV-2 were categorized as (a) asymptomatic SARS-CoV-2 if without COVID-19 symptoms throughout the > 14 days of quarantine, (b) pre-symptomatic SARS-CoV-2 if COVID-19 symptoms started during the quarantine, and (c) false positive contacts if two consecutive follow-up qRT-PCRs were negative after an initial positive SARS-CoV-2 test.Findings: 48,944 COVID-19 patients identified 277,066 contacts who were tested for SARS-CoV-2; upon ascertainment, 3,152 contacts without symptoms were SARS-CoV-2 PCR positive without symptoms, and 50 contacts were false positives. After quarantine, 2928 were classified as asymptomatic and 174 were pre-symptomatic SARS-CoV-2 contacts, with a pre-symptomatic case fatality (11/174) of 6.3%. The average interval between the initial SARS-CoV-2 PCR positive and onset of COVID-19 symptoms was 9.7 days, and the average time from onset of symptoms to death for deceased pre-symptomatic cases was 6.3 days (range = 1 - 35 days).Interpretation: Contact tracing of COVID-19 cases required many contact tracing teams, testing all contacts without COVID-19 symptoms, and quarantine of asymptomatic SARS-CoV-2 positive contacts. Countries with limited contact tracing, testing and quarantine of asymptomatic SARS-CoV-2 infected contacts under-estimate the number of infected asymptomatic SARS-CoV-2 contacts, and their contribution to COVID-19 spread.Funding Statement National Natural Science Foundation of China (82041021), Bill & Melinda Gates Foundation (INV-006371).Declaration of Interests The authors declare they have no conflict of interest.Ethics Approval Statement This study was approved by the Medical Research Ethics Review Committee of Sun Yat-sen University School of Public Health (No. 2020016). Consistent with public health regulations the informed consent was waived because data were collected as part of public health practice associated with the COVID-19 outbreak investigation and response.