Asymptomatic transmission of coronavirus disease 2019 (Covid-19) at a workplace in bangkok metropolitan region, Thailand

Abstract

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has a wide clinical spectrum, ranging from asymptomatic infection to multi-organ system failure. Patients with COVID-19 generally spread the virus during the symptomatic phase. However, data on COVID-19 transmission from patients who did not develop symptoms in the whole course of illness is still limited. The study described an outbreak consisting of six asymptomatic COVID-19 cases in an office workplace, which was not related to family transmission or healthcare settings. The first asymptomatic COVID-19 case was identified by positive SARS-CoV-2 nasopharyngeal swab RT-PCR assay during an active surveillance in the community. Close contact tracing among coworkers of the index case identified five other asymptomatic positive nasopharyngeal swab RT-PCR COVID-19 subjects. SARS-CoV-2 serology assays identified another 15 nasopharyngeal swab RT-PCR negative asymptomatic coworkers on the same floor as the six infected cases. No officer workers on different floors were SARS-CoV-2 positive by serology assays and no family members of the first six asymptomatic COVID-19 cases were positive by nasopharyngeal swab RT-PCR assay. The findings highlight the importance of SARS-CoV-2 transmission from asymptomatic patients in a non-healthcare setting and of serology testing in risk individuals with negative nasopharyngeal swab SARS-CoV-2 RT-PCR assay results.