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Scientists have developed a blood test that distinguishes between viral and bacterial infections in people with respiratory illnesses.

Researchers said the test, which detects a specific genetic "signature" that the patient's immune system expresses as a response to the virus, is accurate about 90 percent of the time.

The technology behind the test is moving closer to clinical use. Researchers believe that the test could help patients get quicker diagnoses and treatments and curb the unnecessary use of antibiotics that don't work against viral infections.

"In instances such as pandemic flu or the corona-virus that has erupted in the Middle East, it's extremely important to diagnose a viral illness far more accurately and speedier than can be done using traditional diagnostics," co-senior author Geoffrey S. Ginsburg, M.D., Ph.D., director of Genomic Medicine and professor of medicine at Duke University School of Medicine, said in a news release. "Current tests require knowledge of the pathogen to confirm infection, because they are strain-specific. But our test could be used right away when a new, unknown pathogen emerges."

Unlike traditional tests that rely on evidence of the pathogen in the blood stream and requires knowledge of that particular bug to detect it, the new test could be used to detect unknown emerging diseases like potential bioterrorism threats.

"This is important not only in viral pandemics where infection may be caused by unknown viruses but also in routine care where the decision to treat or not with antibiotics is paramount," said lead author Aimee K. Zaas, M.D., MHS, associate professor of infectious diseases and international health at Duke.

The latest study involved 102 people in a "real world" setting. All participants arrived at a hospitals emergency department with a fever. Study results revealed 28 had viral infection, 39 had a bacterial infection and 35 were healthy controls. Researchers were able to accurately classify more than 90 percent of the patients as having viral infections or not. The test was able to provide true positive identification of viral infection in 89 percent of the cases and correctly ruled out the negative cases 94 percent of the time.

"This work opens new approaches to diagnosis of infectious diseases," Geoffrey S.F. Ling, M.D., Ph.D., deputy director of the Defense Sciences Office for the Defense Advanced Research Projects Agency (DARPA), said in a news release.

Researchers said the next step is to reduce the amount of time it takes for the test results to be reported. Currently the test takes 12 hours and analyzes about 30 genes.

"We were very pleased that the assay could pick out those with viral infection with a high degree of accuracy," Zaas added. "This is perhaps the most important aspect of this effort - the accuracy of the new test in a real-world setting. It is a major step forward in the test becoming a useful diagnostic to help physicians and patients."

The findings are published in the journal Science Translational Medicine.