The relationship between COVID‐19 viral load and disease severity: A systematic review

INTRODUCTION: Patients with COVID‐19 may present different viral loads levels. However, the relationship between viral load and disease severity in COVID‐19 is still unknown. Therefore, this study aimed to systematically review the association between SARS‐CoV‐2 viral load and COVID‐19 severity. METHODS: The relevant studies using the keywords of “COVID‐19” and “viral load” were searched in the databases of PubMed, Scopus, Google Scholar, and Web of Science. A two‐step title/abstract screening process was carried out and the eligible studies were included in the study. RESULTS: Thirty‐four studies were included from the initial 1015 records. The vast majority of studies have utilized real‐time reverse transcription‐polymerase chain reaction of the nasopharyngeal/respiratory swabs to report viral load. Viral loads were commonly reported either as cycle threshold (C (t)) or log(10) RNA copies/ml. CONCLUSION: The results were inconclusive about the relationship between COVID‐19 severity and viral load, as a similar number of studies either approved or opposed this hypothesis. However, the studies denote the direct relationship between older age and higher SARS‐CoV‐2 viral load, which is a known risk factor for COVID‐19 mortality. The higher viral load in older patients may serve as a mechanism for any possible relationships between COVID‐19 viral load and disease severity. There was a positive correlation between SARS‐CoV‐2 viral load and its transmissibility. Nonetheless, further studies are recommended to precisely characterize this matter.