Duration of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infectivity: When Is It Safe to Discontinue Isolation?

Abstract

Defining the duration of infectivity of SARS-CoV-2 has major implications for public health and infection control practice in healthcare facilities. Early in the pandemic, most hospitals required two negative RT-PCR tests before discontinuing isolation in patients with Covid-19. Many patients, however, have persistently positive RT-PCR tests for weeks to months following clinical recovery and multiple studies now indicate that persistently positive RT-PCRs generally do not reflect replication-competent virus. SARS-CoV-2 appears to be most contagious around the time of symptom onset and infectivity rapidly decreases thereafter to near-zero after about 10 days in mild-moderately ill patients and 15 days in severely-critically ill and immunocompromised patients. The longest interval associated with replication-competent virus thus far is 20 days from symptom onset. This review summarizes evidence-to-date on the duration of infectivity of SARS-CoV-2 and how this has informed evolving public health recommendations on when it is safe to discontinue isolation precautions.

Recommendations for sample pooling on the Cepheid GeneXpert® system using the Cepheid Xpert® Xpress SARS-CoV-2 assay

“…Although Ct values cannot be determined when testing a pooled sample; they will be determined subsequently when the contributing samples are individually tested, and may provide important information on patient infectivity. For example, patients with a Ct value above 34 are unable to be cultured, suggesting decreased transmissibility [15,16]. One challenge that may prevent some point-of-care testing sites from adopting a pooled testing strategy is the lack of mechanical pipettes.…”

Impact of Nasopharyngeal Specimen Quality on SARS-CoV-2 Test Sensitivity

“…The copyright holder for this this version posted December 11, 2020. ; https://doi.org/10.1101/2020.12.09.20246520 doi: medRxiv preprint SARS-CoV-2 Ct values have shown promise as a means to roughly quantify viral burden and so to guide infection control and public health interventions (1,2,(4)(5)(6)(7)(8). However, variability in NP specimen collection may exert large effects on observed SARS-CoV-2 Ct values, limiting these useful applications.…”

“…As the COVID-19 pandemic continues to drive morbidity and mortality around the world, interest has grown in using SARS-CoV-2 reverse-transcription polymerase chain reaction (RT-PCR) cycle of threshold (Ct) values as a means of quantifying viral load (1,2). It has been proposed that SARS-CoV-2 Ct values may correspond with viral burden and infectivity, and that SARS-CoV-2 values may be used to predict disease severity and guide isolation precautions for individuals with COVID-19 (3)(4)(5)(6)(7). SARS-CoV-2 Ct values have been shown to correspond with community COVID-19 burden, and it has also been proposed that community Ct values may help to guide non-pharmaceutical interventions to control COVID-19 (8).…”

COVID-19: Way Forward With Serosurveillance Without Overemphasizing Neutralizing Antibodies

“…For completeness, it is important to mention some of the potential drawbacks regarding serology as a marker of prior exposure. Most importantly, some patients did not develop antibodies despite clearing the virus (14,46), and the duration of detectable antibodies is not clear (24,31,38), although in the largest study today in Iceland the levels of antibodies remained steady for 4 months (through the end of the study). Knowing the duration is important as serology will be a useful tool only if it accurately captures prior exposures.…”

“…Based on the timing of seroconversion with respect to the duration of viable virus shedding, it is likely that the majority of seropositive patients (particularly IgG positive), at least those with mild/moderate infection, are no longer shedding viable virus (31,33). The inability of currently used PCR testing for SARS-CoV-2 RNA lacks important ability to determine the duration of transmissibility, which limits its utility only as the determinant of illness' etiology.…”