RENEE MONTAGNE, HOST:
We have some news now that has medical researchers excited. It's a new test. It requires just one drop of blood, and it can reveal every kind of viral infection a person has ever had, including some they might not know about. NPR's Nell Greenfieldboyce reports on how the test works and what it could mean for your health.
NELL GREENFIELDBOYCE, BYLINE: If you go to a doctor with symptoms that suggest a particular virus, your doctor might order a test for it.
STEVE ELLEDGE: But if you wanted to know about all by viruses, there was really no way to do it.
GREENFIELDBOYCE: Steve Elledge is at Harvard Medical School in the Brigham and Women's Hospital in Boston. His group has just developed a test that can reveal your personal history of viral infections. And, of course, Elledge took the test himself.
ELLEDGE: Well, I learned that I had a - been infected with a number of relatively common viruses and nothing too rare.
GREENFIELDBOYCE: The test looks for antibodies that your immune system produces to viruses it's been exposed to. The test uses about 93,000 bits of virus proteins to fish for those antibodies. It can detect exposure to about 200 families of viruses. For example, there are different families of influenza viruses or of rhinoviruses, which cause the common cold.
ELLEDGE: You could get a rhinovirus infection every winter. You know, you could have 40 of them. And that would show up as one in our analysis 'cause we condense them all into their family.
GREENFIELDBOYCE: Already they've discovered that, on average, people have been infected by viruses from about 10 different families. So far they've screened over 500 people from four continents. Young people had less exposure to viruses than old people. People living in Peru or Thailand were exposed to more viruses than people in the United States.
ELLEDGE: People had seen individual viral differences, but no one had ever looked on this grand of a scale.
GREENFIELDBOYCE: The results are reported in the journal Science. The test costs about 25 bucks, but it's just a research tool for now. Ellen Foxman is a researcher at Yale University School of Medicine who thinks the potential here is exciting. She says scientists suspect viral infections could trigger a number of diseases that involve the immune system, like diabetes, and this test will let them do new studies.
ELLEN FOXMAN: To see if there's some pattern of viral exposures that is actually contributing to that disease that we don't know about.
GREENFIELDBOYCE: But this test does have limitations. If a virus isn't already known to science, it isn't in the test. Nell Greenfieldboyce, NPR News.
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