Abstract
Background: Knowing how long SARS-CoV-2-positive individuals can remain infective is crucial for the design of infection prevention and control strategies. Viral culture is the gold standard for detecting an active-replicative virus and evaluating its infectious potential.
Objective: To assess the correlation of SARS-CoV-2 infectivity with the number of days from symptom onset and the Ct value, using culture as a reference method. Also, to describe a detailed protocol for SARS-CoV-2 culture and immunofluorescence confirmation based on our experience with other respiratory viruses.
Study design: 100 consecutive respiratory samples positive for SARS-CoV-2 by RT-PCR from different subjects were inoculated into VERO E6 cells.
Results: Viral isolation was successful in 58% of samples. The median number of days from symptom onset for culture-positive samples was 2, and 15 for culture-negative samples. Six positive cultures were obtained in patients ≥14 days after symptom onset, all of whom were immunocompromised or with severe COVID-19. The mean Ct value was 12.64 units higher in culture-negative than in culture-positive samples. The probability of successfully isolating SARS-CoV-2 in samples with a Ct value <22 was 100%, decreasing to 3.1% when >27.
Conclusions: Our findings show a significant positive correlation between the probability of isolating SARS-CoV-2 in culture, fewer days of symptoms and a lower RT-PCR Ct value. SARS-CoV-2 infectivity lasts no more than 14 days from symptom onset in immunocompetent individuals. In contrast, in immunocompromised patients or those with severe COVID-19 infectivity may remain after 14 days. Ct value <22 always indicates infectivity.
Keywords: COVID-19; Infectivity; SARS-CoV-2; VERO E6 cells; Viral culture; Viral isolation.
【저자키워드】 COVID-19, SARS-CoV-2, Infectivity, VERO E6 cells, viral culture, Viral isolation, 【초록키워드】 protocol, severe COVID-19, Immunocompromised patients, Symptom, RT-PCR, virus, Immunocompromised patient, respiratory viruses, Probability, Culture, cells, Patient, Isolation, Infection prevention, Immunocompromised, Ct value, gold, VERO E6 cells, immunofluorescence, correlation, viral culture, Prevention and control, Other respiratory viruses, Vero E6, symptom onset, subject, gold standard, positive correlation, positive, reference method, positive individuals, infective, RT-PCR Ct, respiratory sample, inoculated, median, indicate, individuals, SARS-CoV-2-positive individual, 【제목키워드】 immunofluorescence, positive, respiratory sample,