One of the best ways to figure out how far a virus like COVID-19 has spread in a community is to test for it. This step-by-step guide explains how coronavirus swab-the-nose-and-throat tests work, and ...

Polymerase chain reaction (PCR) tests have become routine because of the COVID-19 pandemic, with more than a million PCR tests being carried out daily in the United States alone. What are now commonly ...