The use of rapid flu tests may help curb the overuse of antibiotics, a new study reveals.

Using these tests, doctors could tell within minutes whether a virus or bacteria had caused the illness. Antibiotics are useless against viruses, such as influenza. They are often used for precautionary reasons, particularly if patients have a fever or are elderly, said Dr. Ann Falsey, one of the researchers at Rochester General Hospital and the University of Rochester (NY). Their overuse has helped breed new, drug-resistant strains.

Falsey’s team reviewed the medical records of 166 Rochester hospital patients with documented influenza between 1999 and 2003. Most received antibiotics, but a total of 86% of the patients tested positive for the flu with the rapid flu test. That compares to 99% whose flu was not diagnosed right away. The findings should help convince doctors to not use antibiotics automatically in patients presenting with flu symptoms, researchers say.