2024 Volume 73 Issue 1 Pages 91-98
Although over three years have passed since the outbreak of the coronavirus disease (COVID-19) pandemic, few studies have been conducted to examine the severe acute respiratory syndrome coronavirus 2 RNA copy number and Cq values in specimens from different collection sites in COVID-19 patients. In this study, we aimed to address this knowledge gap. One hundred and forty specimens were collected from nine patients on ventilators with severe COVID-19 symptoms. Cq values were obtained by polymerase chain reaction-capillary electrophoresis, and copy numbers were obtained by conversion based on Ct values measured by reverse transcription quantitative polymerase chain reaction. Strong correlations between the Cq value and the copy number were observed, suggesting that the Cq value can serve as an indicator of the copy number. Copy numbers in oral secretion and sputum samples were higher than those in the nasal cavity and nasopharynx samples, and the sputum viral load was never below the detection sensitivity. The viral load decreased at a lower rate in oral secretions than in other secretions, suggesting that in patients with tracheal intubation, the virus remains in the oral cavity. No significant differences between surviving and deceased cases were observed in copy number or transition, suggesting that factors other than viral load may correlate with the prognosis. These results suggest that, in patients with severe COVID-19, the virus may persist in oral secretions and sputum for a long time, regardless of drug administration or number of days since onset.
