Relationship between the Viral Load in Patients with Different COVID-19 Severities and SARS-CoV-2 Variants

Abstract

SARS-CoV-2 has spread throughout the world since 2019, changing in its genome and leading to the appearance of new variants. This gave it different evolutionary advantages, such as greater infectivity and/or a greater ability to avoid the immune response, which could lead to an increased severity of COVID-19 cases. There is no consistent information about the viral load that occurs in infection with the different SARS-CoV-2 variants, hence, in this study we quantify the viral load of more than 16,800 samples taken from the Mexican population with confirmed diagnosis of COVID-19 and we analyze the relation between different demographic and disease variables. We detected that the viral load caused by different variants differs only in the first two days after the onset of symptoms, being higher when infections are caused by the delta variant and lower when caused by omicron. Furthermore, the viral load appears to be higher in outpatients compared to hospitalized patients or in cases of death. On the other hand, no differences were found in the viral load produced in vaccinated and unvaccinated patients, nor did it differ between genders.

Immune Response to Respiratory Viral Infections

“…The infection may be limited to the upper respiratory tract (URT) or progress to the lower respiratory tract (LRT), also inducing bronchiolitis or pneumonia [ 3 , 4 , 5 ]. The balance between the immune response and the viral infection differs significantly with age, host defense mechanisms, and viral load and properties [ 6 , 7 , 8 ]. Host defense against viruses involves several components of the immune system, including mechanical barriers (i.e., mucosal surfaces) and innate and adaptive immune responses [ 9 ].…”