Most sore throats are caused by a virus and are incorrectly treated with antibiotics, say experts who released new guidelines on the treatment of strep throat.

Of the millions of people each year who see a doctor for a sore throat, only a small percentage actually have a bacterial infection from streptococcus, the Infectious Diseases Society of America said in its report.

"The guidelines promote accurate diagnosis and treatment, particularly in avoiding the inappropriate use of antibiotics, which contributes to drug-resistant bacteria," said lead author, Dr. Stanford T. Shulman of Children's Hospital of Chicago.

The researchers said they see an increase in resistance of strep to azithromycin and cephalosporin.

They said patients should be prescribed penicillin or amoxicillin, but only after the doctor confirms the presence of the bacteria with a rapid antigen detection test, which can provide results in a few minutes.

The IDSA recommends doctors do a followup throat culture on children and adolescents but not on adults, and that antibiotics should not be prescribed while waiting for results.

Strep is not likely when people experience symptoms like a cough, runny nose, hoarseness and mouth sores, which are "strong signs of a viral throat infection," the IDSA said.

The guidelines appear this week in the journal Clinical Infectious Diseases.