The research article by Ferreti, et al, “Quantifying SARS-CoV-2 transmission suggests epidemic control with digital contact tracing”, which appeared in Science Magazine on May 8, 2020 speaks to the critical importance of identifying infection during the presymptomatic period. The authors make the point that transmission resulting from the presymptomatic path could be enough to sustain the epidemic independent of the other pathways.

The attached image from the article provides a visual of the relative contribution of the presymptomatic path to virus transmission. The graph points to the necessity of taking an active posture with respect to presymptomatic transmission and to the importance of Viral Sign.

The full article can be found at


“Transmission occurring rapidly and before symptoms, as we have found, implies that the epidemic is highly unlikely to be contained solely by isolating symptomatic individuals.”

“Specifically, our approaches suggest that between one-third and one-half of transmissions occur from presymptomatic individuals.”