Dynamics of viral RNA load, virus culture, seroconversion & infectivity in COVID-19 patients: Implications on isolation policy

The ongoing SARS-CoV-2 pandemic has spread all over the world due to rapid person-to-person transmission. More information about viral load dynamics and replication is needed for clarity on duration of infectiousness of an individual, along with its implications on transmission. This is important to healthcare facilities and public health authorities in formulating guidance on the duration of isolation for patients and return to work criteria for healthcare workers. The duration of detection of viral RNA by molecular methods in the upper respiratory tract has ranged from 2 to 12 wk. Viral RNA detection by reverse transcription polymerase chain reaction (RT-PCR) does not necessarily mean that the individual is infectious to others, as the detected virus may not be replication competent. Infectious virus is generally not shed beyond 20 days of the onset of symptoms in most patients, including severely ill and immunocompromised, as indicated by failure to isolate replication-competent virus beyond this timeline in available studies. Further, detection of neutralizing antibodies in the serum, although associated with positive RT-PCR, is generally not associated with infectious virus shedding as indicated by negative viral cultures beyond this period. In this review, we analyze the current literature on the dynamics of viral load, culture, seroconversion and their implications on infectivity and the duration of isolation precautions for COVID-19 patients.