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

Abstract

Infectious respiratory particles expelled by SARS-CoV-2 positive patients are attributed to be the key driver of COVID-19 transmission. Understanding how and by whom the virus is transmitted can help implement better disease control strategies. Here we have described the use of a noninvasive mask sampling method to detect and quantify SARS-CoV-2 RNA in respiratory particles expelled by COVID-19 patients and discussed its relationship to transmission risk. Respiratory particles of 31 symptomatic SARS-CoV-2 positive patients and 31 asymptomatic healthy volunteers were captured on N-95 masks layered with a gelatin membrane in a 30-minute process that involved talking/reading, coughing, and tidal breathing. SARS-CoV-2 viral RNA was detected and quantified using rRT-PCR in the mask and in concomitantly collected nasopharyngeal swab (NPS) samples. The data were analyzed with respect to patient demographics and clinical presentation. Thirteen of 31(41.9%) patients showed SARS-COV-2 positivity in both the mask and NPS samples, while 16 patients were mask negative but NPS positive. Two patients were both mask and NPS negative. All healthy volunteers except one were mask and NPS negative. The mask positive patients had significantly lower NPS Ct value (26) compared to mask negative patients (30.5) and were more likely to be rapid antigen test positive. The mask positive patients could be further grouped into low emitters (expelling <100 viral copies) and high emitters (expelling >1000 viral copies). The study presents evidence for variation in emission of SARS-CoV-2 virus particles by COVID-19 patients reflecting differences in infectivity and transmission risk among individuals. The results conform to reported secondary infection rates and transmission and also suggest that mask sampling could be explored as an effective tool to assess individual transmission risks, at different time points and during different activities.

Feasibility and utility of facemask sampling in the detection of SARS-CoV-2 during an ongoing pandemic

“…In this study, our purpose was to assess the utility and feasibility of FMS using materials which were already widely available, such as wound closure strips and surgical facemasks (Table 3 ). Using this method, FMS had a pick-up rate of 62.6–87.5% of patients who were tested within the first 5 days of symptom onset, which is consistent with previous studies [ 10 , 11 ]. Additionally, FMS was able to distinguish symptomatic patients with COVID-19 from those presenting with fever or ARI symptoms without COVID-19.…”

“…Another group used a commercially available gelatine membrane applied on the inner surface of N95 masks, worn by patients for 30 min, and additionally requested participants to perform certain purposeful vocal tasks. Using this, they demonstrated a pick-up rate of 44.8% of concomitantly NPS-positive patients [ 11 ].…”

Variation in Severe Acute Respiratory Syndrome Coronavirus 2 Bioaerosol Production in Exhaled Breath

“…Overall, we observed 71% SARS-CoV-2 RNA positivity in mask samples, which was significantly higher than the previously reported studies (38%–40%) that used different sampling strategies [ 14 , 15 ]. We observed 87% positivity in nasal swabs, which is consistent with the literature, in which nasal swabs are approximately 90%–95% sensitive to nasopharyngeal swabs when collected on the same day, and these samples were collected 2–3 days after the initial positive swab.…”

Viral load of SARS-CoV-2 in droplets and bioaerosols directly captured during breathing, speaking and coughing

“…SARS-CoV-2 RNA has also been detected by sampling masks that participants wore during natural expiratory activities. Samples were gathered by swabbing the mask 33 – 35 or by testing electrostatic filters 36 , gelatin filters 37 or polyvinyl alcohol (PVA) sampling matrix strips 38 placed within the masks. In other studies, samples gathered 10 cm from each participant’s chin 39 , 40 or by sampling EBC 41 were negative for the presence of SARS-CoV-2 RNA by RT-PCR.…”