From Google News

WASHINGTON It happens too often: A doctor isn't sure what's causing someone's feverish illness but prescribes antibiotics just in case, drugs that don't work if a virus is the real culprit.

Now Duke University researchers are developing a blood test to more easily tell when a respiratory illness is due to a virus and not a bacterial infection, hoping to cut the dangerous overuse of antibiotics and speed the right diagnosis.

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It works by taking a fingerprint of your immune system — how its genes are revving up to fight the bug. That's very different from how infections are diagnosed today. And if the experimental test pans out, it also promises to help doctors track new threats.

That viral "signature could be quite powerful, and may be a game-changer," said Dr. Geoffrey Ginsburg, Duke's genomic medicine chief. He leads the team that on Wednesday reported that a study involving 102 people provided early evidence that the test can work.

Today, when symptoms alone aren't enough for diagnosis, a doctor's suspicion guides what tests are performed — tests that work by hunting for evidence of a specific pathogen. Fever and cough? If it's flu season, you might be tested for the flu virus. An awful sore throat? Chances are you'll get checked for strep bacteria. A negative test can leave the doctor wondering what germ to check for next, or whether to make a best guess.

Researchers at a number of universities are trying to harness a fairly recent discovery: As your immune system detects an invading bug, different genes are activated to fend off a viral infection than to fight a bacterial or fungal one. Those subtle molecular changes appear to be occurring even before you feel any symptoms. And they form distinct patterns of RNA and proteins, what's called a genomic fingerprint.

The genomic test proved 89 percent accurate in sorting out who had a virus, and did even better at ruling out those who didn't, Dr. Aimee Zaas, an infectious disease specialist and the Duke lead researcher, reported Wednesday in the journal Science Translational Medicine.

It took 12 hours to get results.