key: cord-0861982-30epn9sy
authors: Pan, Daniel; Sze, Shirley; Abraham, Shalin; Williams, Caroline M; Tang, Julian W; Barer, Mike R; Pareek, Manish
title: Rapid tests for quantification of infectiousness are urgently required in patients with COVID-19
date: 2021-05-12
journal: Lancet Microbe
DOI: 10.1016/s2666-5247(21)00089-6
sha: cc4d8c86c04635e795cf6a48eff412b55ab73c29
doc_id: 861982
cord_uid: 30epn9sy

nan

than the nasopharyngeal tract using specialised matrices embedded within facemasks. 13 The rapid identification of infectious individuals in the community, as well as in hospitals, will be crucial for effective contact tracing of future respiratory virus outbreaks with pandemic potential.

Muge Cevik and colleagues 1 report that for SARS-CoV-2, no study was able to culture live virus from any respiratory samples taken after day 8 or beyond day 9 of symptoms, despite persistently high viral RNA loads. 1 This is a striking finding because, unlike SARS-CoV and MERS-CoV, for which symptom severity correlates to infectiousness, most patients with COVID-19 continue to have worsening symptoms beyond day 9, but might become progressively less infectious. 2, 3 We would like to make two comments about this study. 1 First, none of the 11 studies that attempted to isolate live SARS-CoV-2 in this data synthesis included patients who were severely immunosuppressed. There is emerging evidence showing long-term SARS-CoV-2 culture positivity in this specific cohort (up to 119 days after symptom onset; table), with emergence of mutations that are identical to those found in the South African B.1.351, Brazilian P.1, and Kent B.1.1.7 variants. [4] [5] [6] [7] [8] Increased vigilance is needed to protect immunosuppressed individuals, as well as their close contacts, from being infected.

Second, the authors mention in their discussion that repeat RNA PCR testing in clinical practice might not be indicated to classify patients as no longer infectious. We strongly agree with this statement. Current National Institute for Health and Care Excellence guidance suggests that patients with COVID-19 awaiting an urgent operation can have the procedure postponed if they have a recent positive PCR test. 9 Some countries also require passengers from the UK to have a negative PCR test before flying. 10 We would recommend modifying such criteria to state that patients who have recovered from COVID-19 can have an operation or fly 10 days after their first positive swab, or 10 days after clear symptom onset, with exceptions for those who had severe symptoms or are heavily immunosuppressed. This guidance will require further updating as the evidence evolves, as has been done with the recent removal of repeat testing for hospitalised patients with COVID-19 before discharge to long-term care facilities in December, 2020. 11, 12 Future studies should focus on simpler and faster methods of quantifying the infectiousness of an individual with COVID-19 beyond viral cultures, which are labour intensive and require laboratory facilities with high biosafety levels (ie, category 3 or biosafety level 3 facilities), and for which a cytopathic effect can take 3-6 days to be observed. Cycle threshold values that indirectly provide a quantitative PCR value are not interchangeable between assays, and can be affected by the gene target or targets being assayed, the nucleic acid extraction system, and the PCR amplification biochemistry. One possible strategy could be to sample virus from exhaled breath rather 7 One patient with mantle cell lymphoma who was receiving CD20 bispecific antibody with cyclophosphamide, doxorubicin, and prednisolone 156 119

Data show the number of days after COVID-19 symptom onset that patients were positive for SARS-CoV-2. NAAT=nucleic acid amplification test. *Maximum reported duration. †Values are from five individual patients.

COVID-19 entry requirements

19-guidance-for-stepdown-of-infectioncontrol-precautions-within-hospitals-anddischarging-covid-19-patients-from-hospitalto-home-settings/guidance-for-stepdown -of-infection-control-precautions-anddischarging-covid-19-patients

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