Health authorities have issued a meningococcal warning after a 15-year-old boy attended a concert in the CBD.
The teenage boy was at a concert in Newtown on July 16 to see the punk rock band No Use for a Name.
Doctors are now urging anyone who was at the event to check themselves for symptoms.
Pain in the legs, cold hands and feet as well as abnormal skin colour are among the early signs, while high fever and a blotchy purple-red rash come on later.
People who are concerned should seek medical advice immediately.
Doctors are also reminding people that the vaccine doesn't protest against the main strain of the disease.