Unfortunately, "flesh-eating bacteria," the sensationalized name for an infection properly called "necrotizing fasciitis," is all too real. ("Necrotizing" means causing the death of tissues, "fasciitis" refers to inflammation of the fascia, the connective tissue that surrounds muscles.) Fortunately, these infections are very rare. According to the U.S. Centers for Disease Control and Prevention (CDC), only 650 to 800 cases of the most common type of this disease occur in the U.S. every year, and despite the media attention some of them attract, there's no evidence that the number is increasing.
These infections are described as "flesh-eating" because the bacteria that cause them spread rapidly and destroy the soft tissues they invade. The most common culprit is group a Streptococcus, but other types of bacteria including Klebsiella, Clostridium, E. coli, Staphylococcus aureus and Aeromonas hydrophila can be responsible. Group A strep infections usually are easily treated, but when these (or other) bacteria make particular toxins, they can literally kill the tissues they invade.
The bug that does all the damage gets into the body through a break in the skin – often a minor cut, scrape, burn, insect bite, or puncture. Individuals at highest risk are those with existing health problems such as diabetes, kidney disease, cancer or other conditions that weaken body defenses. However, one case that received widespread publicity this year (2012) was that of a healthy young woman in Georgia who was injured when a zip line she was riding snapped. As a result of her fall, her left calf was badly cut; doctors used 22 staples to close the wound. She was still in pain three days later and went to the emergency room. It took a while to determine that the pain was due to necrotizing fasciitis caused by infection with Aeromonas. The patient, Aimee Copeland, age 24, lost her left leg, her right foot and both her hands before the infection was brought under control.
The infections that cause necrotizing fasciitis aren't always obvious - symptoms generally start within hours after an injury but don't necessarily seem related to the wound. They can include pain and soreness that may feel like a pulled muscle. Other symptoms include fever, chills, fatigue or vomiting; the skin can look inflamed and swell or develop ulcers, blisters or black spots.
Treatment requires powerful intravenous antibiotics that don't always reach all the affected areas. In these cases, the dead infected tissue must be surgically removed as soon as possible in an attempt to halt the progress of the infection.
There is no sure-fire way to prevent necrotizing fasciitis. Promptly treating a cut or other wound can help reduce the risk of any bacterial infection. Cover open wounds with clean, dry bandages until they're healed; don't get into a swimming pool, whirlpool or hot tub if you have an open wound or active infection; and wash your hands often with soap and water.
And bear in mind that despite the scary headlines and shrill sound bites about flesh-eating bacteria, these cases are extremely rare and your risk of experiencing one is very, very low.
Andrew Weil, M.D.