More than half of the 180 confirmed cases have occurred in the Northern Cape and Free State, though the disease has been reported in all nine provinces.
The NCID said it was caused by a virus usually transmitted to humans through bites by the hyalomma tick (or "bontpoot" tick), which has a red body and red-and-white striped legs. It can also be transmitted by contact with infected animal tissues and blood.
Victims develop a sudden fever, muscle and back pain, dizziness, headache, sore eyes and sensitivity to light, accompanied by nausea, vomiting, diarrhoea and abdominal pain. They also experience sudden mood swings and can be confused or aggressive.
The NCID said patients became lethargic after two to four days, developed a fine red and purple rash and suffered large areas of bleeding into the skin. Bleeding may also occur from or into the gut, in urine, and in the nose and gums.