What is necrotizing fasciitis?

Necrotizing fasciitis is a rare bacterial infection that can destroy skin and the soft tissues beneath it, including fat and the tissue covering the muscles (fascia). Because these tissues often die rapidly, a person with necrotizing fasciitis is sometimes said to be infected with "flesh-eating" bacteria. The most common type of bacteria causing necrotizing fasciitis is Streptococcus pyogenes.

When necrotizing fasciitis occurs in the area of the genitals, it is called Fournier gangrene.

Necrotizing fasciitis is very rare but serious. Around 30% of those who develop necrotizing fasciitis die from the disease.¹

Many people who get necrotizing fasciitis are in good health prior to the infection.² Those at increased risk of developing the infection are people who:

• Have a weakened immune system or lack the proper antibodies to fight off the infection.
• Have chronic health problems such as diabetes, cancer, or liver or kidney disease.
• Have cuts, including surgical wounds from operations such as an episiotomy or a hernia repair.
• Recently had chickenpox or other viral infections that cause a rash.
• Use steroid medicines, which can lower the body's resistance to infection.

What causes necrotizing fasciitis?

Necrotizing fasciitis is caused by several kinds of bacteria. The most common cause is infection by a group A streptococcal (GAS) bacterium, most often Streptococcus pyogenes, which also causes other infections such as strep throat and impetigo. Usually the infections caused by these bacteria are mild. But in rare cases the bacteria produce poisons (toxins) that can damage the soft tissue below the skin and cause a more dangerous infection that can spread quickly along the tissue covering the muscle (fascia). The bacteria also can travel through the blood to the lungs and other organs. The disease also may be caused by Vibrio vulnificus. Infection with this bacterium can occur if wounds are exposed to ocean water or contact raw saltwater fish or oysters. Infection also may occur through injuries from handling sea animals such as crabs. These infections are more common in people who have chronic liver diseases such as cirrhosis.

Another type of necrotizing fasciitis may be caused by multiple bacteria found in the intestine. This type most often affects people with diabetes or peripheral arterial disease. Sometimes people who have gunshot injuries, intestinal surgery, or tumors in the lower digestive tract develop necrotizing fasciitis.

A break in the skin allows bacteria to infect the soft tissue. In some cases, infection can also occur at the site of a muscle strain or bruise, even if there is no break in the skin. It may not be obvious where the infection started, because the bacteria may travel through the bloodstream to other parts of the body.

Group A strep bacteria producing the toxins that cause necrotizing fasciitis can be passed from person to person. But a person who gets infected by the bacteria is unlikely to develop a severe infection unless he or she has an open wound, chickenpox, or an impaired immune system.

What are the symptoms?