The case of Necrotizing fasciitis, or "flesh-eating bacteria", that recently occurred to a young Georgia victim is a tragedy and it reminds us that there are always microbes in our environments to infect us. But some proportion and perspective are appropriate here.
Odds that you will be struck by lightning during your life are one in 10,000. The CDC estimates that only one of 400,000 people get necrotizing fasciitis in any one year in the U.S.
Most cases of necrotizing fasciitis occur in persons with health risk factors such as diabetes or compromised immune systems. The most common cause of necrotizing fasciitis is Group A Streptococcus (strep), about 725 cases a year in the U.S. Treatment consists of antibiotics and surgical removal of dead tissues. Around 20% of patients with necrotizing fasciitis caused by Group A strep will die.
Necrotizing fasciitis can be caused by at least six completely different bacteria. It usually starts as a wound infection and spreads to soft subcutaneous tissues and connective tissues (fascia) that enclose muscles, nerves and blood vessels. Infection appears to spread rapidly. Often the pain and tenderness experienced is out of proportion to the size of the wound. Some individuals may initially complain of pain or soreness similar to a pulled muscle. Later the patient may develop fever and chills. The redness of the skin spreads rapidly and the skin may turn dusky, purplish or darker as tissues are destroyed.
The bacteria quickly reproduce in the wound and give off toxins and enzymes that destroy tissues that become gangrenous (dead). Gangrenous tissues must be surgically removed to save the life of the patient. Progress of the disease is very fast and persons who may have it must seek medical attention immediately. Necrotizing fasciitis causes excruciating pain, dangerously low blood pressure, confusion, high fever, and severe dehydration due to the toxins poisoning the body. In addition to tissue decay, these bacteria may cause the rest of the body's organs to go into systemic shock resulting in respiratory failure, heart failure, low blood pressure and kidney failure.
The most recently publicized case in Georgia was not caused by strep but by Aeromonas hydrophila, which is bacteria that can be found in almost all fresh and brackish (slightly salty) waters. It is a natural microbial inhabitant of these waters and does not result from contamination of streams and lakes with sewage or other pollution. This microbe causes infections in fish and amphibians but human infections are extremely rare and should not be a reason to avoid using recreational waters. Aeromonas hydrophila can infect humans as a diarrheal disease of the gut or as necrotizing fasciitis. It is resistant to many common antibiotics.
No matter which microbe may cause necrotizing fasciitis, the best prevention is good hand washing and wound care. Superficial cuts, abrasions and scratches should be washed with soap, rinsed thoroughly with clean water and then covered with clean bandages. Deeper or larger skin trauma must have quick medical attention. If any wound begins to show signs of infection (pus, pain, swelling, redness, warm to touch, inflammation) it is always wise to seek medical attention.
Murray P, Rosenthal K, Kobayashi G, Pfaller M: Medical Microbiology, ed 4, St. Louis, 2002, Mosby, Inc.
Georgia Department of Public Health - Communications Fact Sheet: Necrotizing Fasciitis, May 2012.
Centers for Disease Control: Morbidity and Mortality Weekly Report, Aeromonas Wound Infections Associated with Outdoor Activities -- California, 39:(20); 334, 341, 1990. Martin J, Aeromonas hydrophila: http://web.mst.edu/- microbio/BIO221/A_hydrophila.htm