SARS-CoV-2 RNA shedding lasted as long as 83 days in samples from the respiratory tract and 126 days in stool samples in a systematic review and meta-analysis of data from 79 studies, but viable virus duration was much shorter, with peak viral load occurring within the first week of symptoms.
None of the trials detected live virus 9 days of symptomatic illness, despite persistently high viral loads in the pooled studies involving more than 5,300 patients, and included data on viral load kinetics, duration of viral shedding, or viable virus.
“Our findings suggest that, although patients with SARS-CoV-2 infection might have prolonged RNA shedding of up to 83 days in upper respiratory tract infection, no live virus was isolated from culture beyond day 9 of symptoms despite persistently high viral RNA loads,” wrote researcher Muge Cevik, of the University of St. Andrews, Fife, Scotland, and colleagues in The Lancet.
The findings suggest that the strategy of repeat testing that has been a mainstay of many Covid-19 programs may not be clinically useful, the researchers wrote.
“Duration of infectiousness and subsequent isolation time-line could reflect viral load dynamics and could be counted from symptom onset for 10 days in non-severe cases,” Cevik and colleagues wrote.
Virologist Vincent Munster, PhD, who is chief of the Virus Ecology Unit for the National Institute of Allergy and Infectious Disease, said the meta-analysis offers reassuring evidence that the 2-week quarantine window for patients who are positive for Covid-19 is generally sufficient.
“This study is helpful, in that it affirms that the 14-day quarantine is probably adequate in 99% of cases,” he told BreakingMED.
Munster recently reported on the case of a severely immunocompromized 71-year-old woman with leukemia who shed virus for 105 days and was infectious for at least 70 days. The woman never developed symptoms of Covid-19.
He said while it is important for clinicians to recognize that severely immunocompromised patients may remain infectious for longer periods, for the vast majority of patients the duration of infectiousness is relatively short.
“These patients are outliers with severe underlying conditions, which completely block their immune response,” he said.
In their systematic review and meta-analysis, Cevik and colleagues examined the viral load dynamics of SARS-CoV-2, duration of viral RNA shedding using RT-PCR and viable virus shedding in body fluids. They also compared SARS-CoV-2 viral dynamics with the viruses SARS-CoV and MERS-CoV.
The researchers calculated the mean duration of viral shedding for every study identified that met the inclusion criteria and they applied the random-effects model to estimate a pooled effect size. A weighted meta-regression with an unrestricted maximum likelihood model was used to assess the effect of potential moderators on the pooled effect size.
A total of 79 SARS-CoV-2 studies were included in the analysis (5,340 people), along with 8 SARS-CoV (1,858 participants) and 11 studies of MERS-CoV (799 participants).
Among the main findings:
- The mean duration of SARS-CoV-2 RNA shedding was 17.0 days (95% CI, 15.5-18.6; 43 studies, 3229 individuals) in upper respiratory tract; 14.6 days (95% CI, 9.3-20.0; 7 studies, 260 individuals) in lower respiratory tract; 17.2 days (95% CI, 14.4-20.1; 13 studies, 586 individuals) in stool; and 16.6 days (95% CI, 3.6-29.7; two studies, 108 individuals) in serum samples.
- The maximum shedding duration was 83 days in the upper respiratory tract, 59 days in the lower respiratory tract, 126 days in stools, and 60 days in serum.
- Pooled mean SARS-CoV-2 shedding duration was positively associated with age (slope 0.304 [95% CI, 0.115-0.493]; P=0.0016).
“No study detected live (SARS-CoV-2) virus beyond day 9 of illness, despite persistently high viral loads, which were inferred from cycle threshold values,” Cevik and colleagues wrote. “SARS-CoV-2 viral load in the upper respiratory tract appeared to peak in the first week of illness, whereas that of SARS-CoV peaked at days 10–14 and that of MERS-CoV peaked at days 7–10.”
The researchers concluded that their review “provides detailed understanding about the evidence available so far on viral dynamics of SARS-CoV-2 RNA and has implications for pandemic control strategies and infection control practices.”
“Although SARS-CoV-2 RNA shedding can be prolonged in respiratory and stool samples, viable virus is short-lived, with culture success associated with viral load levels,” they wrote. “Most studies detected the SARS-CoV-2 viral load peak within the first week of illness…
“These findings highlight that isolation practices should be commenced with the start of first symptoms, including mild and atypical symptoms that precede more typical Covid-19 symptoms. However, given potential delays in the isolation of patients , effective containment of SARS-CoV-2 might be challenging even with an early detection and isolation strategy.”
- SARS-CoV-2 RNA shedding lasted as long as 83 days in samples from the respiratory tract and 126 days in stool samples in a systematic review and meta-analysis of data from 79 studies, but viable virus duration was much shorter.
- None of the trials detected live virus beyond 9 days of symptomatic illness, despite persistently high viral loads in the pooled studies involving more than 5,300 patients.
Salynn Boyles, Contributing Writer, BreakingMED™
The researchers reported no funding source for this study, and they declared no relevant competing interests.
Cat ID: 190
Topic ID: 79,190,254,930,791,932,190,926,192,927,151,928,925,934