Group A streptococcal infection is caused by a bacterium in the shape of a string of round balls that belongs to the group A serotype of the various streptococcus varieties. Group A streptococcal infections are also called hemolytic streptococcal infections.

The patient develops a sudden fever of 38℃ or higher accompanied by a sore throat. A red rash appears on the skin, and the patient may develop a red tongue with spots making it look like a strawberry (known as "strawberry tongue"). In severe cases, group A hemolytic streptococcus can cause a variety of diseases such as pharyngitis (strep throat), tonsillitis, impetigo^*1 in addition to the usual skin rash, cellulitis,^*2 middle ear inflammation, pneumonia, septic arthritis, osteomyelitis, and meningitis. Group A hemolytic streptococcus is also known as a causative bacterium of streptococcal toxic shock syndrome, which causes tissue necrosis (death of tissue) and shock.