COVID-19: sputum can be SARS-CoV-2 positive up to 5 weeks, feces up to 2 weeks postdischarge

  • Chen C & et al
  • Ann Intern Med
  • 31 Mar 2020

  • curated by Liz Scherer
  • Clinical Essentials
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Takeaway

  • SARS-CoV-2 can be detectable in feces for up to ~2 weeks and in sputum for up to ~5 weeks after pharyngeal swabs are clear.
  • Clear pharyngeal swabs are used to indicate suitability for hospital discharge.
  • Whether discharged patients pose potential transmission risk based on existing hospital discharge criteria is unclear.

Why this matters

  • These authors say that the results "raise concern about whether patients with negative pharyngeal swabs are truly virus-free, or sampling of additional body sites is needed." 
  • They also emphasize, however, that sample positivity does not indicate that a patient continues to pose a risk for infection to others.
  • This study did not involve culture from samples.

Key results

  • 22/133 patients had initial or follow-up negative pharyngeal positive sputum or fecal sample pairing.
  • 545 specimens were tested (209 pharyngeal, 262 sputum, 74 feces).
  • 22 participants: 18 ages 15-65 years and 4 10 years.
  • 14 were male, 11 had known travel or exposure history, 5 had >1 preexisting condition.
  • 100% met discharge criteria: afebrile >3 days, respiratory symptom resolution, improved chest CT findings, 2 consecutive negative reverse transcription (RT)-qPCR SARS-CoV-2 respiratory samples at least 24 hours apart. 
  • After clear pharyngeal samples, sputum remained positive for up to 39 days and feces for up to 13 days.

Study design

  • Retrospective analysis of paired RT-qPCR pharyngeal swabs and sputum or feces samples obtained from hospitalized patients with confirmed COVID-19, Beijing, China.
  • Funding: Beijing Science and Technology Commission.

Limitations

  • No defined schedule serial samples analyzed.
  • Retrospective.