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Health

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New test aims to better detect viral infections

– 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.

It works by taking a fingerprint of your immune system – how its genes are revving up to fight the bug. And if the experimental test pans out, it also promises to help doctors track brand-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. Moreover, rapid in-the-office tests aren’t always accurate and can miss infections. So patients may have blood or other samples sent to labs to try to grow any lurking bacteria and tell if it’s to blame, additional testing that can take days.

“This is something we struggle with every day,” said Dr. Octavio Ramilo, infectious disease chief at Nationwide Children’s Hospital in Columbus, Ohio, who wasn’t involved in the new study. Particularly with children, a respiratory virus and a bacterial infection “in the beginning look completely alike,” he added.

Hence 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 Duke team discovered 30 genes that are switched on in different ways during a viral attack. The test essentially is a freeze-frame to show “what those genes are doing at the moment in time that it’s captured,” explained Duke lead researcher Dr. Aimee Zaas, an infectious disease specialist.

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