Viral RNA Shedding and Transmission Potential of Asymptomatic and Pauci-symptomatic COVID-19 Patients

Dear Editor,

Congratulations for doing such a good study. Samaddar et al. [1] summarized that viral RNA shedding in exhaled breath decreased progressively and patients became negative after 6 days of positive reverse transcription polymerase chain reaction (RT-PCR) testing. The authors’ conclusion that the duration of isolation should be reduced to 6 days as per the above findings is a matter of dispute.

These results needs to be cautiously interpreted, as even after 2 negative tests, there is a 47% probability of having coronavirus disease 2019 (COVID-19) in a patient with high pretest probability of disease [2]. A positive test can be useful to rule in disease, but a negative test does not “rule out” disease [3]. So even 2 negative tests on RT-PCR do not guarantee that the asymptomatic patient cannot transmit the disease, as the sensitivity of the test is moderate. A study done by Hu et al. showed that viral transmission from asymptomatic patients can occur for up to 21 days [4]. They also reported that patients can have positive tests after 2 consecutive negative tests [4]. A study done by Zhou et al. showed that during hospitalization asymptomatic patients showed higher viral loads in the first week and that the duration of viral shedding is similar to that of symptomatic patients [5].

The work by Samaddar et al. was not planned to study the incidence of COVID-19 disease in contacts of asymptomatic patients. Hence, the interpretation of decreased duration of isolation in COVID-19 patients cannot be validated in the absence of evidence that the contacts of asymptomatic patient do not become positive for COVID-19. It would be wrong to use these findings to conclude that duration of isolation should be reduced to 6 days, as the authors rushed to this conclusion without taking into account the sensitivity and specificity of the RT-PCR test itself.