LAUSR

Background : SARS-CoV-2 seems to be mainly transmissible via respiratory droplets. We compared the time-dependent SARS-CoV-2 viral load in serial pharyngeal swab and exhaled breath (EB) samples of hospitalized COVID-19 patients. Methods : In this prospective proof of concept study, we examined hospitalized patients initially tested positive for SARS-CoV-2. The screening consisted of collecting paired oronasopharyngeal swab and EB specimens taken at different days of hospitalization. The EB collection was performed through a noninvasive simple method using an electret air filter-based device. SARS-CoV-2 RNA detection was determined with qRT-PCR. Results : Of 187 serial samples taken from 15 hospitalized patients, 87 oronasopharyngeal swabs and 70 of the 100 EB specimens tested positive. Comparing the number of SARS-CoV-2 copies, the viral load of the oronasopharyngeal swabs (n=87) was significantly higher (CI 99%, p<<0,001) than the viral load of the EB samples (n=70). The mean viral load per swab was 7.97 × 106 (1.65 × 102-1.4 × 108), whereas EB samples showed 2.47 × 103 (7.19 × 101-2.94 × 104) copies per 20 times exhaling. Viral loads of paired oronasopharyngeal swab and EB samples showed no correlation. Conclusions : Assessing the infectiousness of COVID-19 patients merely through pharyngeal swabs might not be accurate. Exhaled breath could represent a more suitable matrix for evaluating the infectiousness and might allow screening for superspreader individuals and widespread variants such as the Delta variant.