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Asymptomatic and symptomatic SARS-CoV-2 infections in close contacts of COVID-19 patients: a seroepidemiological study

Our take —

This study was a sero-epidemiological study of 284 close contacts of 14 confirmed COVID-19 patients in Yancheng, China. Contract tracing was used to identity close contacts of case, and individuals were tested by RT-PCR using throat swab samples. Among close contacts, 41% (113) provided plasma serum samples during quarantine for antibody testing using ELISA. Overall, 20 infections were identified in close contacts, of which 40% (8/20) were asymptomatic. This study supports the value in antibody testing use for the identification of cases to inform control measures.

Study design

Case Series

Study population and setting

This research letter reported on 284 close contacts of 14 confirmed COVID-19 patients in Yancheng, China. Contract tracing was used to identity close contacts of case, and individuals were tested by RT-PCR using throat swab samples. Among close contacts, 41% (113) provided plasma serum samples during quarantine for antibody testing using ELISA.

Summary of Main Findings

Overall, 20 infections were identified in close contacts when using both RT-PCR and antibody testing, of which 40% (8/20) were asymptomatic. In total, 10 close contacts tested positive using RT-PCR and among those who were positive, 2 were asymptomatic cases. Antibody testing identified an additional 10 (8.8%, 10/113) close contacts with evidence of infection. Among those identified through antibody testing, 4 reported mild symptoms and 6 were asymptomatic.

Study Strengths

Inclusion of antibody testing among close contacts allowed for detection of cases that were not identified through RT-PCR testing.

Limitations

Given only 41% of participants provided serum samples for antibody testing, the proportion of individuals in the total sample with antibodies may be underestimated. Overall, limited detail on methods are provided in the publication, which limits a reader’s ability to critically review.

Value added

Inclusion of antibody testing among close contacts allowed for detection of cases that were not identified through RT-PCR testing.

This review was posted on: 30 July 2020