SARS-CoV-2 Virus Culture and Subgenomic RNA for Respiratory Specimens from Patients with Mild Coronavirus Disease

Abstract

We investigated 68 respiratory specimens from 35 coronavirus disease patients in Hong Kong, of whom 32 had mild disease. We found that severe acute respiratory syndrome coronavirus 2 and subgenomic RNA were rarely detectable beyond 8 days after onset of illness. However, virus RNA was detectable for many weeks by reverse transcription PCR.

Keywords: COVID-19; China; Hong Kong; SARS-CoV-2; coronavirus; coronavirus disease; infectivity; mild disease; respiratory infections; severe acute respiratory syndrome coronavirus 2; subgenomic RNA; viral RNA load; virus culture; viruses; zoonoses.

Figure 1

Severe acute respiratory syndrome coronavirus 2 RNA load, virus culture, and days after onset of illness in respiratory specimens and duration of illness for patients with mild coronavirus disease, Hong Kong. ¡ indicates samples positive by virus culture and × indicates samples negative by virus culture. Red indicates 2 critically ill patients and 1 patient who died; black indicates mild, moderate, or asymptomatic infections. The limit of detection of the viral N gene RNA was 1 log₁₀ copies/mL; undetectable virus load is indicated as the limit of detection. N, nucleoprotein.

Figure 2

Severe acute respiratory syndrome coronavirus 2 viral RNA load, virus culture, and subgenomic virus RNA (sgRNA) in relation to days after onset of illness for patients with mild coronavirus disease, Hong Kong. Red indicates culture and sgRNA positive, green indicates culture and sgRNA negative, yellow indicates culture positive and sgRNA negative, brown indicates culture negative and sgRNA positive, and gray indicates culture positive and no sgRNA data (because of insufficient specimen).