Could alternative technologies meet these new testing demands? Considerable evidence indicates that they could. An especially compelling argument can be made for harnessing powerful DNA-sequencing machines, each of which could test tens or hundreds of thousands of samples a day for viral RNA. The needed sequencing machines are already in wide use—for medical research and detection of mutations in patients with cancers or other diseases—in numerous academic and commercial laboratories around the country. Several teams of investigators are devising and testing new protocols that could achieve the new aims.

In one proposal that our group considered to reach this kind of scale, samples from each person would be given a unique identifier—in essence, a bar code. Thousands of samples would be mixed together and sequenced, allowing the determination of which samples contained viral RNA and which did not. Scientists now have extensive experience in using this approach—for instance, to measure amounts of thousands of different cellular RNAs in millions of individual cells pooled in a single tube—building confidence that the method should work. Sequencing has not been used previously at this scale for clinical tests, primarily because its enormous capacity has not been needed, but the FDA has used the method to survey the food supply for contaminating pathogenic organisms.

The use of such sequencing methods has a notable shortcoming: the need to transport samples to places where the sequencing machines reside, creating expenses and delays.