Spatial and Temporal Virus Load Dynamics of SARS-CoV-2: A Single-Center Cohort Study

Abstract

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused an ongoing pandemic. Reverse transcription polymerase chain reaction (RT-PCR) is the gold standard for the detection of SARS-CoV-2 and has been applied to different specimen types. Understanding the virus load and virus detection frequency in different specimen types is important to improve diagnosis and estimate the duration of potential infectivity. We conducted a retrospective single-center cohort study on hospitalized and outpatients with SARS-CoV-2 infection. We analyzed the frequency of virus detection, virus load, and duration of the virus excretion in upper and lower respiratory specimens as well as stool and plasma. We found that the frequency of SARS-CoV-2 detection, the virus load, and duration of virus excretion was higher in lower respiratory tract (LRT) than in upper respiratory tract (URT) specimens. The duration of virus excretion was longer in patients requiring intensive care unit (ICU) admission. In conclusion, LRT specimens are the most appropriate specimen type for the detection and follow-up of SARS-CoV-2 infection. Duration of virus excretion is longer in severe cases of SARS-CoV-2 infection.

Airborne transmission of respiratory viruses

“…Because viruses are enriched in small aerosols (<5 μm), they can travel deeper into and be deposited in the lower respiratory tract. The viral load of SARS-CoV-2 has been reported to be higher and the virus persists longer in the lower respiratory tract compared with the upper respiratory tract ( 164 , 165 ). Initiation of an infection in the lower respiratory tract adds technical challenges in diagnosing patients because current screening commonly collects samples from the nasopharyngeal or oral cavity using swabs.…”

SARS-CoV-2 RT-qPCR Test Detection Rates Are Associated with Patient Age, Sex, and Time since Diagnosis

“…Therefore, such negative results do not necessarily indicate a false-negative result, especially as later positive results may be of high Ct values and may result from fragmented RNA and not from infectious viral particles 24 . Moreover, at the patient-specific level, as the viral load is associated with time since onset of symptoms, sex and age [25][26][27][28][29][30][31][32][33] , it has been proposed that detection rates might also depend on demographics, but current studies lacked statistical power for quantifying such dependencies 18,[34][35][36][37][38][39] .…”

Estimation of viral kinetics model parameters in young and aged SARS-CoV-2 infected macaques

“…There is some clinical evidence supporting the finding of differing viral dynamics at different locations in the respiratory tract. While not specifically age-related, a larger meta-analysis noted that severe illness was linked to longer viral shedding in the upper respiratory tract, but not in the lower respiratory tract [48], with a smaller study finding a similar result [49]. Other modelling studies are also finding differences in viral kinetics parameters between measurements taken at different locations in the respiratory tract in both macaques [41] and humans [50,51].…”