SARS-CoV-2 Cannot Be Contained by Manual Contact Tracing Alone
Klaus Mergener, MD, PhD, FASGE, reviewing Ferretti L, et al. Science 2020 Mar 31.
Because effective treatments for COVID-19 are not yet available, we rely upon isolation of infected individuals, contact tracing, and quarantine as key approaches to contain the pandemic. The current modeling study comes to the sobering conclusion that these measures may not be good enough to achieve this goal.
The authors categorized the major routes of infection transmission as “symptomatic,” “presymptomatic” (transmission from individuals before they develop symptoms), “asymptomatic” (transmission from individuals who never develop symptoms), and “environmental” (eg, transmission via contaminated surfaces). Based on the latest inputs from published reports, they concluded that, in stark contrast to the first SARS outbreak of 2003, the SARS-CoV-2 virus is often transmitted early during the course of the disease, and manual contact tracing can be expected to come too late to contain its spread. They proposed that a hypothetical mobile-phone app capable of immediately identifying all recent contacts of a newly diagnosed individual, and automatically notifying these contacts and medical providers, could speed up this process sufficiently to result in sustainable epidemic suppression.
COMMENT
In addition to its thought-provoking primary conclusion of the utility of a phone app in the management of the SARS-CoV-2 outbreak, this report from one of the world’s premier epidemiology teams provides us with a detailed update on the relative frequency of transmission routes. From what is known to date, it can be assumed that approximately 45% of all infections are being transmitted during the presymptomatic phase of the illness, another 40% from sy ges of their disease, and only 10% are estimated to occur from environmental sources, including surface contamination.
Note to readers: At the time we reviewed this paper, its publisher noted that it was not in final form and that subsequent changes might be made.
Klaus Mergener, MD, PhD, FASGE
CITATION(S)
Ferretti L, Wymant C, Kendall M, et al. Quantifying SARS-CoV-2 transmission suggests epidemic control with digital contact tracing. Science 2020 Mar 31. (Epub ahead of print) (https://doi.org/10.1126/science.abb6936)
