Viral load of SARS-CoV-2 across patients and compared to other respiratory viruses

Abstract

RT-PCRs to detect SARS-CoV-2 RNA is key to manage the COVID-19 pandemic. We analyzed SARS-CoV-2 viral loads from 22'323 RT-PCR results according to samples types, gender, age, and health units. Viral load did not show any difference across age and appears to be a poor predictor of disease outcome. SARS-CoV-2 viral load showed similar high viral loads than the one observed for RSV and influenza B. The importance of viral load to predict contagiousness and to assess disease progression is discussed.

Keywords: COVID-19; Cycle threshold; Diagnostic; RT-PCR; SARS-CoV-2; Viral load.

Fig. 1

A: Histogram of SARS-CoV-2 viral loads. B: Time-course analyses of SARS-CoV-2 viral loads across time. Viral loads mirrored the reported COVID-19 infections in Switzerland.

Fig. 2

A: Viral loads of 14 respiratory viruses compared to SARS-CoV-2. HMPV: Human-metapneumovirus, HPIV1-4: Human Parainfluenza Viruses 1–4, InfA and B: Influenza viruses A and B; RSV: Respiratory Syncytial Virus. m represents the median, n the number of observations, and the percentage of positive test is presented. Statistical significance of viral loads of SARS-CoV-2 was assessed against the other viruses. B–C: Viral loads distribution of SARS-CoV-2 across sex and age showed comparable values among all groups. D: Initial viral loads of SARS-CoV-2 in different hospital departments. ICU first and ICU max correspond to respectively the first or highest sample recorded for patients latter admitted to the ICU. Statistical significance of viral loads was assessed against the SU samples (upper stars), and against the ICU (lower stars). E: Distribution of viral loads across different specimens. Statistical significance of viral loads was assessed against the NPS samples AS: anal swab, BAL: bronchoalveolar lavage, CSF cerebrospinal fluid, NTS: nasal-throat swab, TS: throat swab. P-values: ns: p > 0.05, ∗: p ≤ 0.05, ∗∗; p ≤ 0.01, ∗∗∗; p ≤ 0.001, ∗∗∗∗: p ≤ 0.0001.