There are many types of bacteria that can cause the “flesh-eating disease” called necrotizing fasciitis. Public health experts believe group A Streptococcus (group A strep) are the most common cause of necrotizing fasciitis. Early symptoms of necrotizing fasciitis can include: A red, warm, or swollen area of skin that spreads quickly. Severe pain, including pain beyond the area of the skin that is red, warm, or swollen. Fever. Necrotizing fasciitis is a very serious illness that requires care in a hospital. Antibiotics and surgery are typically the first lines of defense if a doctor suspects a patient has necrotizing fasciitis.