Working Paper Review Version 2 This version is not peer-reviewed

Review of Infective Dose, Routes of Transmission, and Outcome of COVID-19 Caused by the SARS-CoV-2 Virus: Comparison with Other Respiratory Viruses

Version 1 : Received: 24 July 2020 / Approved: 25 July 2020 / Online: 25 July 2020 (16:21:53 CEST)
Version 2 : Received: 21 October 2020 / Approved: 22 October 2020 / Online: 22 October 2020 (10:34:02 CEST)
Version 3 : Received: 5 December 2020 / Approved: 7 December 2020 / Online: 7 December 2020 (11:36:05 CET)

A peer-reviewed article of this Preprint also exists.

Journal reference: Epidemiology and Infection 2021
DOI: 10.1017/S0950268821000790


Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is pandemic. Prevention and control strategies require an improved understanding of SARS-CoV-2 dynamics. We did a rapid review of the literature on SARS-CoV-2 viral dynamics with a focus on infective dose. We sought comparisons of SARS-CoV-2 with other respiratory viruses including SARS-CoV-1 and MERS-CoV. We examined laboratory animal, and human studies. The literature on infective dose, transmission, and routes of exposure was limited specially in humans, and varying endpoints were used for measurement of infection. We propose the minimum infective dose of COVID-19 in humans, is higher than 100 particles, possibly slightly lower than the 700 particles estimated for H1N1 influenza. Despite variability in animal studies, there was some evidence that increased dose at exposure correlated with higher viral load clinically, and severer symptoms. Higher viral load measures did not reflect COVID-19 severity. Aerosol transmission seemed to raise the risk of more severe respiratory complications in animals. An accurate quantitative estimate of the infective dose of SARS-CoV-2 in humans is not currently feasible and needs further research. Further work is also required on the relationship between routes of transmission, infective dose, co-infection, and outcomes.


infective dose; SARS-CoV-2; COVID-19; respiratory viruses; viral load; viral dynamics


BIOLOGY, Anatomy & Morphology

Comments (1)

Comment 1
Received: 22 October 2020
Commenter: Sedighe Karimzadeh
Commenter's Conflict of Interests: Author
Comment: Revision  (cross refrencing and linking the content of tables with main text)
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