Viral load detection on surgical mask worn by patients with acute respiratory virus infection

Objectives: This study investigated viral load (VL) in surgical mask worn by adult patients infected with respiratory viruses. Methods: Surgical masks were dissected into six pieces: inner (N1) and outer (N2) layers at the nose, inner (M1) and outer (M2) layers at the mouth position, and full-thickness on right (RS) and left (LS) sides for VL assay. The results were correlated with VL of nasopharyngeal specimens (NPS) and patients' demographics. Results: Among 230 patients infected with influenza A virus (n = 91), RSV (n = 61), and SARS-CoV-2 (n = 78) from April 1 to August 31, 2023, 90.9 % (209/230) were from the medical specialty. Of the 230 surgical masks collected, viral RNA was detected in 79.1 % at one or more sites, with 75.7 % positive at N1 or M1, 55.2 % positive at N2 or M2, and 29.6 % exhibiting viral RNA at all sites. VL in NPS was correlated with N1 (Pearson's correlation: 0.229, p = 0.007) and M1 (0.169, p = 0.031). The mean VL at N1 (3.2 ± 1.5 log10 copies/cm2 of mask) was significantly higher than M1 (2.6 ± 1.3 log10 copies/cm2, p < 0.001) and N2 (2.7 ± 1.3 log10 copies/cm2, p = 0.003). Significant differences in VL were observed across two layers of the mask in RSV patients, but not in influenza A or SARS-CoV-2-infected patients. SARS-CoV-2-infected patients exhibited significantly lower VL at RS and LS sites than influenza A or RSV-infected patients. Conclusions: Viral RNA was detected in the outer layer over 50 % of masks used by infected patients infected with influenza A, RSV, and SARS-CoV-2. The contamination may be due to shedding from the wearer's respiratory tract and improper handling of the masks, highlighting the potential risks associated with mask handling and disposal. Contamination of surgical masks worn by patients infected with different respiratory viruses warrants further investigation.