Doctors frequently prescribe antibiotics to treat viruses.
Oregon state officials say this could lead to dangerous antibiotic resistance.
Prescribing antibiotics for non-bacterial diseases has been on the decline for years, but its still a problem.
For example, diseases like bronchitis are caused by a virus and rarely require antibiotics.
According to the Oregon Health Authority, in 2014 55% of bronchitis patients were prescribed an antibiotic.
Ninety-percent of those got a broad-spectrum drug which attacks a wide range of different bacteria.
That increases the risk of developing resistance to the drug.
Using antibiotics for viral infections can also lead to dangerous side affects like diarrhea or vomitting.