Exhaled SARS-CoV-2 quantified by face-mask sampling in hospitalised patients with covid-19

Abstract

Background Nasopharyngeal samples (NPS) are the mainstay of COVID-19 diagnosis. However, the extent to which assay signals relate to exhaled virus is unknown. We investigated the use of novel, non-invasive face-mask sampling (FMS) to detect exhaled SARS-CoV-2 RNA in two studies. Methods In an outbreak study (cohort 1), we performed FMS and NPS for 21 consecutive days after diagnosis on six healthcare workers who were screened positive for SARS-CoV-2. In a second hospitalised cohort (cohort 2), we performed FMS on 47 patients within 24 hours of a positive diagnosis. COVID-19 severity was graded according to WHO recommendations. Findings In cohort 1, SARS-COV-2 was detected by FMS in 10/40 (25%) samples (4/6 individuals), with no correlation between NPS and FMS RNA signals. All samples were negative by day 14 post diagnosis. Sustained FMS positivity with higher viral RNA signals showed a trend towards disease severity. In cohort 2, 19/47 (40%) individuals exhaled SARS-CoV-2 RNA extending over five orders of magnitude. FMS positive participants were older (positive: median age [IQR] 71 [61-84] vs negative: 61 [45-73], p=0.04) with more comorbidities (positive: 2 [1-3] vs negative: 1 [0-2], p<0.001) and have active cough (positive: 68% vs negative: 24%, p=0.003) and breathlessness (positive: 74% vs negative: 32%, p=0.005) during sampling, compared to FMS negative patients. Of five patients who were FMS positive and asymptomatic at time of sampling, two died of severe COVID-19 pneumonia within one month of follow up. Interpretation FMS detects exhaled SARS-COV-2, with stronger signals in those who develop severe disease.

Non-invasive adapted N-95 mask sampling captures variation in viral particles expelled by COVID-19 patients: Implications in understanding SARS-CoV2 transmission

“…The results indicate that while mask-based sampling is not appropriate for use in the diagnosis of COVID-19, it may be a useful method to quantify transmission risks. The results are similar to those of a recent study by another group that investigated the SARS-CoV-2 virus in hospitalized severe COVID-19 patients in an older age group and observed an almost 40% positivity rate and an association between virus detection in respiratory particles with the severity of the disease [ 18 ]. The current study however could not explain this association to severity as all the enrolled patients were younger (median age 42) and with mild to moderate disease.…”

Practical Indicators for Risk of Airborne Transmission in Shared Indoor Environments and their Application to COVID-19 Outbreaks

“…B can be expressed as B 0 x r B , where B 0 and r B are the volumetric breathing rate of a sedentary susceptible person in the age group of 41-<51 years (numerically also the average for all age groups) and the relative breathing rate enhancement factor (vs. B 0 ) for an activity with a certain physical intensity and for a certain age group (see Table SI-2b for detail). E p0 is uncertain, likely highly variable across the population, and variable over time during the period of infectiousness (33,37,(39)(40)(41). It may also increase due to new virus variants such as the COVID-19 B1.1.7 variant, that are more contagious, assuming that the increased contagiousness is due to increased viral emission or reduced infectious dose (both of which would increase the quanta emission rate) (42,43).…”

Learning from COVID-19 to reimagine tuberculosis diagnosis

“…For example, improved and affordable polyester swabs and new approaches to sampling using saliva, mouthwash, oral swabs, and absorbent strips in face masks have shown promise for COVID-19 sample collection and are now being tried for tuberculosis. 3,4 An easy to obtain sample that also could be used to detect other pathogens (such as SARS-CoV-2) would be revolutionary for tuberculosis.…”