SARS-CoV-2: Viral Loads of Exhaled Breath and Oronasopharyngeal Specimens in Hospitalized Patients with COVID-19

Background: SARS-CoV-2 seems mainly transmissible via respiratory droplets. We compared the timedependent SARS-CoV-2 viral load in serial pharyngeal swab with exhaled breath (EB) samples of hospitalized COVID-19 patients. Methods: In this prospective proof of concept study, we examined hospitalized patients who initially tested positive for SARS-CoV-2. Paired oronasopharyngeal swab and EB specimens were taken at different days of hospitalization. EB collection was performed through a simple, noninvasive method using an electret air filter-based device. SARS-CoV-2 RNA detection was determined with real-time quantitative reverse transcription polymerase chain reaction. Results: Of 187 serial samples from 15 hospitalized patients, 87/87 oronasopharyngeal swabs and 70/100 EB specimens tested positive. Comparing the number of SARS-CoV-2 copies, the viral load of the oronasopharyngeal swabs was significantly higher (CI 99%, P<<0,001) than for EB samples. The mean viral load per swab was 7.97 x10(6) (1.65 x10(2) -1.4 x10(8)), whereas EB samples showed 2.47 x10(3) (7.19 x10(1)2.94 x10(4)) 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 infectiousness and might allow screening for superspreader individuals and widespread variants such as Delta. (C) 2021 The Author(s). Published by Elsevier Ltd on behalf of International Society for Infectious Diseases.