Lacking vaccines, countries have relied on multiple non-pharmaceutical interventions to control COVID-19 transmission. Despite the urging of the World Health Organization (WHO) in March to "test, test, and test," policy makers disagree on on how much testing is optimal. A new study, by Ravindra Prasan Rannan-Eliya and coauthors from the Institute for Health Policy in Colombo, Sri Lanka, uses data from multiple online sources to quantify testing impact on COVID-19 transmissibility in 173 countries and territories (accounting for 99 percent of the world's cases) between March and June 2020.
The authors found that among interventions, testing intensity had the greatest influence: a tenfold increase in the ratio of tests to new cases reported reduced average COVID-19 transmission by 9 percent. The authors note that this helps explain why countries such as China, Australia, and New Zealand achieved near elimination of COVID-19 and why lockdowns and other interventions failed to slow spread of the virus in others, such as India and Peru.
"Even the wealthiest countries, such as the US, UK, and Qatar, cannot expand testing and tracing fast enough to achieve epidemic control," the authors conclude. "Early and continuous aggressive testing to keep incidence within capacity to test, trace and isolate may be the best implementation of flattening the curve."