One blood test analyzing less than a single drop of blood can now reveal every virus people have over their lifetime, according to a new study.

A new experimental test called VirScan can detect the 206 virus species known to infect humans and more than 1,000 known virus strains just by testing a small amount of blood, according to the journal Science. Scientists tested VirScan on almost 600 people on four continents and detected an average of 10 strains per person, many of which were common like the cold or flu. But at least two people tested positive for 84 strains.

The new blood test could help doctors trace how viruses spread, and scientists say they believe the test could be expanded as new ones are discovered.

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