Why Testing Speed Matters

And why the U.S. backlog is not ideal

A new study published in the journal The Lancet Public Health underscores the need for fast testing as a means to control the Covid-19 pandemic. The researchers of the study used mathematical modeling to determine the effectiveness of conventional and app-based contact tracing strategies on Covid-19 transmission. They conclude that the speed of testing is the most important factor for successful contract tracing, and quelling the spread of Covid-19. If Covid-19 testing is delayed by even just three days or more after a person develops symptoms, the researchers say that even the most thorough contact tracing strategy will come up short. The study authors distilled their findings in a press release about the findings, and I’m sharing those findings here (R refers to R0 or “R-naught,” an indicator of how easily a disease spreads from person to person in a community):

• Even if all contacts are successfully traced, a delay of three days or more between symptom onset and testing will not reduce onward transmission of the virus sufficiently to control further spread, according to modeling study.
• In the best-case scenario, with zero delays and at least 80% of contacts traced, the R number is reduced from 1.2 to around 0.8, and 80% of onward transmission per person diagnosed could be prevented.
• For conventional contact tracing to work, test results need to be delivered within a day of an individual developing symptoms.