Frequent, rapid testing could turn national COVID-19 tide within weeks

Testing half the population weekly with inexpensive, rapid-turnaround COVID-19 tests would drive the virus toward elimination within weeks—even if those tests are significantly less sensitive than gold-standard clinical tests, according to a new study published today by CU Boulder and Harvard University researchers.Such a strategy could lead to “personalized stay-at-home orders” without shutting down restaurants, bars, retail stores and schools, the authors said.“Our big picture finding is that, when it comes to public health, it’s better to have a less sensitive test with results today than a more sensitive one with results tomorrow,” said lead author Daniel Larremore, an assistant professor of computer science at CU Boulder. “Rather than telling everyone to stay home so you can be sure that one person who is sick doesn’t spread it, we could give only the contagious people stay-at-home orders so everyone else can go about their lives.”For the study, published in the journal Science Advances, Larremore teamed up with collaborators at CU’s BioFrontiers Institute and the Harvard T.H. Chan School of Public Health to explore whether test sensitivity, frequency, or turnaround time is most important to curb the spread of COVID-19.It’s time to shift the mentality around testing from thinking of a COVID test as something you get when you think you are sick to thinking of it as a vital tool to break transmission chains and keep the economy open.”–Dan LarremoreThe researchers scoured available literature on how viral load climbs and falls inside the body during an infection, when people tend to experience symptoms, and when they become contagious.They then used mathematical modeling to forecast the impact of screening with different kinds of tests on three hypothetical scenarios: in 10,000 individuals; in a university-type setting of 20,000 people; and in a city of 8.4 million.When it came to curbing spread, they found that frequency and turnaround time are much more important than test sensitivity.For instance, in one scenario in a large city, widespread twice-weekly testing with a rapid but less sensitive test reduced the degree of infectiousness, or R0 (“R naught”), of the virus by 80%.