The first sign of infection may be a small, reddish, painful spot or bump on the skin. This quickly changes to a very painful bronze- or purple-colored patch that grows rapidly. The center may become black and die off. The skin may break open and ooze fluid. The wound may quickly grow in less than an hour.

Symptoms may include general ill feeling, fever, sweating, chills, nausea, dizziness, profound weakness, and finally shock. Without treatment, death can occur rapidly.

How the skin and tissue look can help the doctor diagnose a necrotizing soft tissue infection. Often a patient will be diagnosed in the operating room by a surgeon. Imaging tests, such as CT scans, are sometimes helpful.

Tests performed on blood, fluids, or tissue from the area may determine the bacteria that is causing the infection.