The pandemic coronavirus disease 2019 (COVID-19) is characterized by systemic infection and multiorgan dysfunction. The association between the kinetics of viral load and clinical outcome in severe COVID-19 patients has not been well established. A retrospective study was performed on clinical specimens from 188 hospitalized severe COVID-19 patients involved in the LOTUS China trial. A total of 578 paired throat swab (TS) and anal swab (AS) samples were collected. Viral load was measured by using quantitative real-time PCR. Viral RNA was detected in 193 (33.4%) TS and 121 (20.9%) AS samples. A higher viral RNA load was found in TS than in AS, with means of 1.0×10 6 and 2.3×10 5 copies/ml, respectively. The median number of days from symptom onset to positive virus detection in AS samples was significantly lower in non-survivors than in survivors (14 days vs 19 days, P=0.007).

Systematic quantitative assessment of the interactions between different respiratory viruses is pivotal for the prevention of infectious diseases and the development of vaccine strategies. Our data showed stable interactions among respiratory viruses at human population level, which are season irrelevant.