Highlights 8.1% of COVID-19 patients were mechanically ventilated in the first outbreak in Osaka. The 30-day mortality rate of mechanically ventilated COVID-19 patients was 24.0%. Among these, 97% of patients were intubated within 14 days from clinical onset. Age ≥65 years and men were associated with a higher 30-day mortality rate. Among these, the median duration of viral RNA shedding from onset was 35 days.

Background We investigated factors associated with prolonged viral clearance of SARS-CoV-2 among non-severe adult patients in Osaka, Japan. A total of 706 laboratory-confirmed COVID-19 patients were enrolled in this longitudinal observational study between 29 January 2020 and 31 May 2020, across 62 hospitals and three non-hospital recuperation facilities. Methods Logistic regression analysis was performed to investigate the factors associated with prolonged (29 days: upper 25% in duration) viral clearance of SARS-CoV-2. Linear regression analysis was conducted to assess these factors 14 days after symptom onset. Results The median duration of viral clearance was 22 days from symptom onset. After adjustment for sex, age, symptoms, comorbidity, and location of recuperation, comorbidities were associated with prolonged duration: (OR, 1.77 [95% CI, 1.11–2.82]) for one, (OR, 2.47 [95% CI, 1.32–4.61]) for two or more comorbidities. Viral clearance 14 days after symptom onset was 3 days longer for one comorbidity and 4 days longer for two or more comorbidities compared to clearance when there was no comorbidity. Conclusion The presence of comorbidity was a robust factor associated with a longer duration of viral clearance, extending by 3 to 4 days compared to patients with no comorbidity.