Blood test can tell you every virus you’ve ever had

Curious how many viruses have invaded your body over the course of your life? Now you can know. Researchers have developed a DNA-based blood test that can determine a person’s viral history, a development they hope could lead to early detection of conditions, such as hepatitis C, and eventually help explain what triggers certain autoimmune diseases and cancers. The new test, known as VirScan, works by screening the blood for antibodies against any of the 206 species of viruses known to infect humans, according to a study published Thursday in the journal Science. The immune system, which churns out specific antibodies when it encounters a virus, can continue to produce those antibodies decades after an infection subsides. VirScan detects those antibodies and uses them as a window in time to create a blueprint of nearly every virus an individual has encountered. It’s a dramatic alternative to existing diagnostic tools, which test only...