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New data suggests saliva superior to nasal swab for early detection

Chris Brookes at University of Illinois Urbana Champaign (UIUC) has published a new paper with colleagues from Johns Hopkins and UMass.

Daily sampling of early SARS-CoV-2 infection reveals substantial heterogeneity in infectio
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The study was made possible by the existence of the highly sensitive surveillance saliva covidShield test implemented at UIUC. This surveillance testing program was leveraged to enroll symptomatic, pre-symptomatic and asymptomatic individuals.

The study investigated the viral dynamics of SARS-CoV-2 infections and viral RNA shedding through a longitudinal sampling of both nasal swab and saliva in 60 individuals for 14 consecutive days.

Chris and his team used viral dynamics mechanistic models and found.

  1. The viral dynamics in nasal and saliva samples were distinct from each other in most individuals

  2. In nasal samples the viral genome loads decreased rapidly after the peak, however in saliva the post-peak viral genome load decreased initially at a slower rate

  3. In most individuals (41 out of the 54 analysed) viral genome shedding peaked at least 1 day earlier in saliva than in nasal samples. In contrast the peak in nasal shedding preceded the saliva peak by at least 1 day in only 3 of 54 individuals.

While the study size is small the results provide an explanation of why saliva could be a superior sample-type for the early detection of SARS-CoV-2 infections compared with nasal swabs.

In New Zealand we are currently attempting to stamp out low prevalence rate of infections to regain elimination status with the current focus on accelerating the vaccination (35% at the time of posting). In this context we should be deploying our most sensitive tests on sample-types that will lead to early detection and isolation with guaranteed fast turnaround times that can be deployed at higher frequencies.

That is why the Rako Science saliva test is needed. We remain the only diagnostically validated saliva test in New Zealand.

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