ABSTRACT
Objective: Understanding the minimum infective dose is significant for risk assessment in the performance of suitable infection control strategies in healthcare centers. However, the literature lacks strong evidence regarding this value for severe acute respiratory syndrome coronavirus 2. Therefore, the aim of this study was to investigate the minimum infectious dose of coronavirus disease 2019. Methods: We searched the databases of PubMed, Scopus, Web of Science, and Cochrane and retrieved all the relevant literature by 25 July 2021. The records were downloaded into the EndNote software and underwent title/abstract and full-text screenings. A summary of included studies was organized into tables for further analysis, interpretation, and drafting of the results. Results: Nineteen studies including the laboratory data on human and animal hosts were selected based on the eligibility criteria. All the literature reported on the infective dose, particularly in humans. The main methods for measurement of infection were through tissue culture infectious dose (TCID50) and counting plaque-forming units. The range of minimum infective was 1.26-7 × 106.25 PFU. Conclusion: In this study, we have presented a range of minimum infective doses in humans and various animal species. Such numbers can possibly vary between the individuals based on numerous demographic, immunologic, or other factors.
ABSTRACT
Objective: Understanding the minimum infective dose is significant for risk assessment in the performance of suitable infection control strategies in healthcare centers. However, the literature lacks strong evidence regarding this value for severe acute respiratory syndrome coronavirus 2. Therefore, the aim of this study was to investigate the minimum infectious dose of coronavirus disease 2019. Methods: We searched the databases of PubMed, Scopus, Web of Science, and Cochrane and retrieved all the relevant literature by 25 July 2021. The records were downloaded into the EndNote software and underwent title/ and full-text screenings. A summary of included studies was organized into tables for further analysis, interpretation, and drafting of the results. Results: Nineteen studies including the laboratory data on human and animal hosts were selected based on the eligibility criteria. All the literature reported on the infective dose, particularly in humans. The main methods for measurement of infection were through tissue culture infectious dose (TCID50) and counting plaque-forming units. The range of minimum infective was 1.26–7 × 106.25 PFU. Conclusion: In this study, we have presented a range of minimum infective doses in humans and various animal species. Such numbers can possibly vary between the individuals based on numerous demographic, immunologic, or other factors.
ABSTRACT
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 (Ct ) or log10 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.