Stable "Salivary Viral Road Ratios" in Individuals Infected With Omicron Variants

SARS-CoV-2 infects the oral and salivary glandular epithelia, leading to release of progeny viruses to shed into saliva. This causes the persistent spread of COVID-19 since the outbreak of the Omicron variants. Viral spread may be mainly attributable to the aerosol transmission of cell-free virions in saliva droplets <5 μm in diameter. However, no data exist on how cell-free virions in the saliva change over time. We, therefore, examined temporal changes in the proportion of cell-free virions shed into saliva relative to whole saliva in individuals infected with the SARS-CoV-2 Omicron variant.

This study analyzed three indices, total viral load in whole saliva, cell-free virion load in centrifuged supernatant, and "salivary viral load ratio", in 14 subjects infected with SARS-CoV-2 Omicron variant on days 1, 4, and 7 after symptom onset. The "saliva viral load ratio" was calculated by dividing the number of cell-free virions in the centrifuged supernatant by the total number of viruses detected in the whole saliva.

The viral load in whole saliva and in the salivary supernatant considerably decreased with time since day 1. However, unexpectedly regarding "salivary viral load ratio," no substantial difference was observed among the collection dates.

Determining the chronological dynamics of salivary cell-free viral load and "salivary viral load ratio" is important for monitoring aerosol transmission. Individuals infected with Omicron variants remain potent to render aerosol transmission until COVID-19 is cured. This will alert health care providers to consider "salivary viral load ratio" as an indicative measure of the likelihood of aerosol transmission in the very early stages of viral infection outbreaks.