SARS-CoV-2 detection, viral load and infectivity over the course of an infection

J Infect. 2020 Sep;81(3):357-371. doi: 10.1016/j.jinf.2020.06.067. Epub 2020 Jun 29.


Objectives: To summarise the evidence on the detection pattern and viral load of SARS-CoV-2 over the course of an infection (including any asymptomatic or pre-symptomatic phase), and the duration of infectivity.

Methods: A systematic literature search was undertaken in PubMed, Europe PubMed Central and EMBASE from 30 December 2019 to 12 May 2020.

Results: We identified 113 studies conducted in 17 countries. The evidence from upper respiratory tract samples suggests that the viral load of SARS-CoV-2 peaks around symptom onset or a few days thereafter, and becomes undetectable about two weeks after symptom onset; however, viral loads from sputum samples may be higher, peak later and persist for longer. There is evidence of prolonged virus detection in stool samples, with unclear clinical significance. No study was found that definitively measured the duration of infectivity; however, patients may not be infectious for the entire duration of virus detection, as the presence of viral ribonucleic acid may not represent transmissible live virus.

Conclusion: There is a relatively consistent trajectory of SARS-CoV-2 viral load over the course of COVID-19 from respiratory tract samples, however the duration of infectivity remains uncertain.

Keywords: COVID-19; Coronavirus; Infectivity; RNA; Review; SARS-CoV-2; Viral load.

Publication types

  • Systematic Review

MeSH terms

  • Adult
  • Asymptomatic Infections / epidemiology
  • Betacoronavirus / pathogenicity*
  • COVID-19
  • Child
  • Coronavirus Infections / epidemiology
  • Coronavirus Infections / virology*
  • Feces / virology
  • Humans
  • Limit of Detection
  • Pandemics
  • Pneumonia, Viral / epidemiology
  • Pneumonia, Viral / virology*
  • RNA, Viral
  • SARS-CoV-2
  • Severity of Illness Index
  • Sputum / virology
  • Time Factors
  • Viral Load*
  • Virus Shedding


  • RNA, Viral