In the context of community transmission where continued testing is impractical, available evidence at this time indicates that an interim strategy based on time-since-illness-onset and time-since-recovery can be implemented to establish the end of isolation. Practical application of a symptom-based strategy cannot prevent all infections.
At this time, data are limited regarding how long persons shed infectious SARV-CoV-2 RNA after infection. Key findings are summarized here.
- Viral burden measured in upper respiratory specimens declines after onset of illness (CDC unpublished data, Midgely 2020, Young 2020, Zou 2020, Wölfel 2020).
- At this time, replication-competent virus has not been successfully cultured more than 9 days after onset of illness. The statistically estimated likelihood of recovering replication-competent virus approaches zero by 10 days (CDC unpublished data, Wölfel 2020, Arons 2020).
- As the likelihood of isolating replication-competent virus decreases, anti-SARS-CoV-2 IgM and IgG can be detected in an increasing number of persons recovering from infection (Wölfel 2020).
- Attempts to culture virus from upper respiratory specimens have been largely unsuccessful when viral burden is in low but detectable ranges (i.e., Ct values higher than 33-35)(CDC unpublished data).
- Following recovery from clinical illness, many patients no longer have detectable viral RNA in upper respiratory specimens. Among those who continue to have detectable RNA, concentrations of detectable RNA 3 days following recovery are generally in the range at which replication-competent virus has not been reliably isolated by CDC (CDC unpublished data, Young 2020).
- No clear correlation has been described between length of illness and duration of post-recovery shedding of detectable viral RNA in upper respiratory specimens (CDC unpublished data, Midgely 2020, Wölfel 2020).
- Infectious virus has not been cultured from urine or reliably cultured from feces (CDC unpublished data, Midgely 2020, Wölfel 2020); these potential sources pose minimal if any risk of transmitting infection and any risk can be sufficiently mitigated by good hand hygiene.
For an emerging pathogen like SARS-CoV-2, the patterns and duration of illness and infectivity have not been fully described. However, available data indicate that shedding of SARS-CoV-2 RNA in upper respiratory specimens declines after onset of symptoms. At 10 days after illness onset, recovery of replication-competent virus in viral culture (as a proxy of the presence of infectious virus) is decreased and approaches zero. Although persons may produce PCR-positive specimens for up to 6 weeks (Xiao, 2020), it remains unknown whether these PCR-positive samples represent the presence of infectious virus. After clinical recovery, many patients do not continue to shed SARS-CoV-2 viral RNA. Among recovered patients with detectable RNA in upper respiratory specimens, concentrations of RNA after 3 days are generally in ranges where virus has not been reliably cultured by CDC. These data have been generated from adults across a variety of age groups and with varying severity of illness. Data from children and infants are not presently available.
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