The U.S. Food and Drug Administration on 19 July approved testing pooled batches of samples for the COVID-19 virus, a strategy supporters say could help screen more people faster and at less cost than through individual tests. The strategy saves reagents by combining samples from four people and running a single test. If the batch tests positive, remaining sample material from each of the four individuals is tested separately. Pooled samples have been used successfully to scale up testing in Germany, China, and other countries. But U.S. states hardest hit by COVID-19 may fail to benefit: The approach conserves reagents only if the rate of positive tests is about 10% or less. As of 20 July, 12 states, including Arizona, Florida, and Texas, had a higher positive rate, according to data from Johns Hopkins University.