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. 2021 Jul 30;73(Suppl 2):S170-S176.
doi: 10.1093/cid/ciaa1442.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Transmission Dynamics Should Inform Policy

Muge Cevik  1 , Julia L Marcus  2 , Caroline Buckee  3 , Tara C Smith  4
Affiliations

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Transmission Dynamics Should Inform Policy

Muge Cevik et al. Clin Infect Dis. .

Abstract

It is generally agreed that striking a balance between resuming economic and social activities and keeping the effective reproductive number (R0) below 1 using nonpharmaceutical interventions is an important goal until and even after effective vaccines become available. Therefore, the need remains to understand how the virus is transmitted in order to identify high-risk environments and activities that disproportionately contribute to its spread so that effective preventative measures could be put in place. Contact tracing and household studies, in particular, provide robust evidence about the parameters of transmission. In this Viewpoint, we discuss the available evidence from large-scale, well-conducted contact-tracing studies from across the world and argue that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission dynamics should inform policy decisions about mitigation strategies for targeted interventions according to the needs of the society by directing attention to the settings, activities, and socioeconomic factors associated with the highest risks of transmission.

Keywords: COVID-19; SARS-CoV-2; coronavirus; novel coronavirus; transmission.

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Figures

Figure 1.
Figure 1.
Factors influencing transmission dynamics. Transmission depends on several factors, including contact pattern (duration of contact, gathering, proximity, activity), environment (outdoor, indoor, ventilation), host-related infectivity/susceptibility pattern (ie, viral load in relation to disease course, severity of illness, age), and socioeconomic factors (ie, crowded housing, job insecurity, poverty). Virus infectivity and differences between other viruses and host immune factors are not discussed in this review. (This figure was created by the authors based on available literature about SARS-CoV-2 transmission dynamics.) Abbreviation: SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.
Figure 2.
Figure 2.
SARS-CoV-2 viral load dynamics and period of infectiousness. Incubation period (time from exposure to symptom onset) of 6 days (2–21 days), peak viral load levels documented from day 0 (symptom onset) to day 5, infectious period starts before symptom onset up to 10 days (this may be extended in patients with severe illness), and RNA shedding continues for a prolonged period of time but culturable virus has been identified up to day 9 of illness. (This figure was created by the authors on Biorender, https://biorender.com based on available literature about SARS-CoV-2 viral load dynamics.) Abbreviations: max, maximum; PCR, polymerase chain reaction; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.
See this image and copyright information in PMC

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