Strep Throat, Streptococcal pharyngitis, is a disease that causes a sore throat, pharyngitis. It is an infection with a germ called Group A Streptococcus bacteria. Strep throat is a bacterial throat infection that can make your throat feel sore and scratchy. Only a small portion of sore throats are the result of strep throat. It's important to identify strep throat for a number of reasons.