Journal Article

Proportion of asymptomatic infection among COVID-19 positive persons and their transmission potential: A systematic review and meta-analysis

Winters, Nicholas, Bastos, Mayara, Menzies, Dick, Perlman-Arrow, Sara, Campbell, Jonathon R., Fregonese, Federica, Yanes-Lane, Mercedes

2020

Overview

The study objective was to conduct a systematic review and meta-analysis on the proportion of asymptomatic infection among coronavirus disease 2019 (COVID-19) positive persons and their transmission potential. We searched Embase, Medline, bioRxiv, and medRxiv up to 22 June 2020. We included cohorts or cross-sectional studies which systematically tested populations regardless of symptoms for COVID-19, or case series of any size reporting contact investigations of asymptomatic index patients. Two reviewers independently extracted data and assessed quality using pre-specified criteria. Only moderate/high quality studies were included. The main outcomes were proportion of asymptomatic infection among COVID-19 positive persons at testing and through follow-up, and secondary attack rate among close contacts of asymptomatic index patients. A qualitative synthesis was performed. Where appropriate, data were pooled using random effects meta-analysis to estimate proportions and 95% confidence intervals (95% CI). Of 6,137 identified studies, 71 underwent quality assessment after full text review, and 28 were high/moderate quality and were included. In two general population studies, the proportion of asymptomatic COVID-19 infection at time of testing was 20% and 75%, respectively; among three studies in contacts it was 8.2% to 50%. In meta-analysis, the proportion (95% CI) of asymptomatic COVID-19 infection in obstetric patients was 95% (45% to 100%) of which 59% (49% to 68%) remained asymptomatic through follow-up; among nursing home residents, the proportion was 54% (42% to 65%) of which 28% (13% to 50%) remained asymptomatic through follow-up. Transmission studies were too heterogenous to meta-analyse. Among five transmission studies, 18 of 96 (18.8%) close contacts exposed to asymptomatic index patients were COVID-19 positive. Despite study heterogeneity, the proportion of asymptomatic infection among COVID-19 positive persons appears high and transmission potential seems substantial. To further our understanding, high quality studies in representative general population samples are required.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Asymptomatic / Asymptomatic infection / Asymptomatic Infections - epidemiology / Betacoronavirus - isolation & purification / Biology and Life Sciences / Canada / Carrier state (Communicable diseases) / Confidence intervals / Control / Coronavirus Infections - diagnosis / Coronavirus Infections - epidemiology / Coronavirus Infections - transmission / Coronavirus Infections - virology / Coronaviruses / COVID-19 / Cross-sectional studies / Databases, Factual / Disease transmission / Epidemics / Epidemiology / Funding / Heterogeneity / Humans / Infection control / Infections / Influence / Management / Medicine and Health Sciences / Meta-analysis / Methods / Nursing / Occupational health / Pandemics / Physical Sciences / Pneumonia, Viral - diagnosis / Pneumonia, Viral - epidemiology / Pneumonia, Viral - transmission / Pneumonia, Viral - virology / Population studies / Prevalence / Public health / Qualitative analysis / Quality assessment / Quality control / Research and Analysis Methods / Restrictions / SARS-CoV-2 / Secondary data analysis / Severe acute respiratory syndrome coronavirus 2 / Signs and symptoms / Supervision / Systematic review / Ultrasonic testing / Viral diseases