"In early March, as diagnostics struggled to keep up with the spread of coronavirus across the United States, chemical engineer Howard Salis felt compelled to help. To speed up testing, he decided to try a powerful sequencing approach that had revolutionized the pace of genomics research. About three weeks later, Salis’s team of synthetic biologists at Pennsylvania State University in University Park came up with a way to test samples from nearly 20,000 people in one run. Their method adds individual ‘molecular barcodes’ to clinical samples before pooling them and using next-generation sequencing to decode them all at once. The barcodes then allow the researchers to identify which samples tested positive. Other teams have released details of similar mass-testing approaches, including the biotechnology start-up firm Octant in Emeryville, California, and researchers at the Broad Institute3. Because DNA sequencers can read out hundreds of millions of DNA snippets at once, researchers estimate that sequencing-based tests could be used to analyse up to 100,000 samples in one run. By contrast, a standard PCR machine can test just dozens or hundreds of samples at the same time. But these sequencing tests take time — at least 12 hours — and require specialized equipment in centralized facilities. Getting millions of samples delivered to those facilities isn’t trivial."