Asymptomatic Subclinical Cases of Coronavirus Disease 2019 without Viral Transmission in Three Independent Families

Abstract

Purpose: There is increasing evidence indicating that considerable fractions of cases of SARS-CoV-2 infection are asymptomatic. We traced three asymptomatic clusters to investigate the infectivity of subclinical cases of coronavirus disease 2019 (COVID-19).

Patients and methods: Three medical staff who were asymptomatic were diagnosed with coronavirus disease 2019 by serological tests. Their close contacts were systematically evaluated based on COVID-19-related symptoms, nucleic acid tests, serological tests, and chest computed tomography (CT) as needed to determine if they were infected by SARS-CoV-2.

Results: None of the staff's close contacts, including 10 family members, were infected by the indexes, even though no protective measures were taken.

Conclusion: The infectivity of asymptomatic subclinical infection patients of coronavirus disease 2019 seems to be low.

Keywords: COVID-19; SARS-CoV-2; asymptomatic; close contact; infectivity.

Figure 1

Chest computed tomography performance of the indexes and contact tracing investigation of their contacts. (A and B) completely normal computed tomography of Case 1 and Case 2; (C) a slight single subpleural patch on the left side of Case 3 (yellow arrow); (D) contact tracing investigation of three clusters. The blue color indicates contacts living with indexes in the same apartment, eating together but sleeping in different rooms; the red color indicates persons with the closest contact with the indexes—living in the same apartment, eating together, and sleeping in the same rooms. None of the contacts were infected, according to their symptoms and the nucleic acid and serologic tests.