US study shows how rapid testing could cripple COVID within weeks

November 23, 2020

Exploring whether different parameters such as test sensitivity, frequency, or turnaround time helps curb the spread of COVID-19 the most has led researches at the University of Colorado-Boulder (CU-Boulder) and Harvard University to believe that rapid-turnaround testing would drive the coronavirus toward elimination soonest.

The tests could be significantly less sensitive than gold-standard clinical tests and still keep super-spreader places like restaurants, bars, retail stores, sports/concert stadiums, and schools from shutting down, as only the contagious would be under “personalised stay-at-home orders” and leave the rest free to go about  their business.

Earlier on, Daniel Larremore, an assistant professor of computer science at CU-Boulder and colleagues had studied how viral load climbs and falls inside the body during an infection such that affects when the person experiences symptoms or becomes contagious.

They also used mathematical modeling to forecast the impact of screening with different kinds of COVID-19 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.

The researchers found that test frequency and turnaround time were much more important than test sensitivity when it came to curbing spread of the virus and saving lives. One scenario showed how widespread twice-weekly testing with a rapid, less sensitive test reduced the degree of infectiousness, or R0 (R naught), of the virus by 80%; while twice-weekly testing with a more sensitive PCR (polymerase chain reaction) test reduced infectiousness by only 58%.

Another scenario, in which 4% of individuals in a city were already infected, rapid testing three out of four people every three days reduced the number ultimately infected by 88% and was “sufficient to drive the epidemic toward extinction within six weeks.”

The rapid tests used the study are affordable contagiousness tests, costing as little as US$1 each to return results in only 15 minutes, instead of days. Larremore surmised that rapid testing could be key to breathing life back into the US economy which has been struggling in the wake of the pandemic.

“Less than .1% of the current cost of this virus would enable frequent testing for the whole of the US population for a year – within a few weeks we could see this outbreak going from huge numbers of cases to very manageable levels,” said Dr. Michael Mina, an assistant professor of epidemiology at the Harvard T.H. Chan School of Public Health.

In this case, even if half of Americans tested themselves weekly using government-provided DIY test kits and self-isolated if positive, the result would be profound, Mina said.

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