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

Malik, Madiha; Kunze, Ann-Cathrin; Bahmer, Thomas; Herget-Rosenthal, Stefan; Kunze, Thomas

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 × 10(6) (1.65 × 10(2)-1.4 × 10(8)), whereas EB samples showed 2.47 × 10(3) (7.19 × 10(1)-2.94 × 10(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 the infectiousness and might allow screening for superspreader individuals and widespread variants such as the Delta variant.