Necrotizing Fasciitis

Necrotizing fasciitis (NF) is also called the flesh-eating disease. It is a rare condition in which bacteria destroy tissues underlying the skin. This tissue death, called necrosis or gangrene, spreads rapidly. This disease can be fatal in as little as 12 to 24 hours.

The Centers for Disease Control and Prevention (CDC) estimates that there are between 650 and 800 cases each year in the United States. Necrotizing fasciitis mostly affects adults. The average age of patients is between 38 and 45 years. Males are three times more likely to be affected. About half of all patients diagnosed with NF were previously strong and healthy. Some people, however, are at greater risk of developing NF, including people with diabetes, heart disease, and other disorders that affect blood circulation; drug addicts and alcoholics; people with weakened immune systems, including those who have received organ transplants; and people with HIV infection are most at risk.

Most often the bacteria enter the body through an opening in the skin, quite often a very minor opening, even as small as a paper cut, a staple puncture, or a pin prick. It can also enter through weakened skin, such as a bruise, blister, or abrasion. It can also happen following a major trauma or surgery, and in some cases there appears to be no identifiable point of entry.

Necrotizing fasciitis is an apt descriptor, meaning the infection appears to devour body tissue. Media reports increased in the middle and late 1990s, but the disease is not new. It first appeared between the 1840s to 1870s. Dr. B. Wilson, first termed the condition necrotizing fasciitis in 1952. However, the disease had been occurring for many centuries before it was described in the 1800s. Indeed, Hippocrates described it more than three millennia ago and thousands of reports exist from the Civil War. There are many terms used to describe necrotizing fasciitis, including flesh-eating bacterial infection or flesh-eating disease; suppurative fasciitis; dermal, Meleney, hospital or Fournier's gangrene; and necrotizing cellulitis.

Necrotizing fasciitis is divided into two types. Type I is caused by anaerobic bacteria, with or without the presence of aerobic bacteria. Type II, also called hemolytic streptococcal gangrene, is caused by group A streptococci; other bacteria may or may not be present. The disease may also be called synergistic gangrene.

Type I fasciitis typically affects the trunk, abdomen, and genital area. For example, Fournier's gangrene is a “flesh-eating” disease in which the infection encompasses the external genitalia. The arms and legs are most often affected in type II fasciitis, but the infection may appear anywhere.

The two most important factors in determining whether a person will develop necrotizing fasciitis are the virulence (ability to cause disease) of the bacteria and the susceptibility (ability of a person's immune system to respond to infection) of the person who becomes infected with this bacteria.

In nearly every case of necrotizing fasciitis, a skin injury precedes the disease. As bacteria grow beneath the skin's surface, they produce toxins. These toxins destroy superficial fascia, subcutaneous fat, and deep fascia. In some cases, the overlying dermis and the underlying muscle are also affected.

Initially, the infected area appears red and swollen and feels hot. The area is extremely painful, which is a prominent feature of the disease. Over the course of hours or days, the skin may become blue-gray, and fluid-filled blisters may form. As nerves are destroyed the area becomes numb. An individual may develop dangerously low blood pressure. Multiple organ failure may occur, quickly followed by death.

Many different types of bacteria can cause this infection. A very severe and usually deadly form of necrotizing soft tissue infection is due to Streptococcus pyogenes, which is sometimes called flesh-eating bacteria. Necrotizing soft tissue infection develops when the bacteria enters the body, usually through a minor cut or scrape. The bacteria begin to grow and release harmful substances (toxins) that kill tissue and affect blood flow to the area. As the tissue dies, the bacteria enter the blood and rapidly spread throughout the body.

Symptoms of necrotizing fasciitis include skin that is red, swollen, and hot to the touch; fever; chills; nausea and vomiting; and diarrhea. The infection may spread rapidly and it can quickly become life threatening. Affected individuals may also go into shock and have damage to skin, fat, and the tissue covering the muscle, referred to as gangrene. Necrotizing fasciitis can lead to organ failure and death.

Although necrotizing fasciitis is somewhat rare, some studies have indicated that about 25% of patients die from the progression of the condition. In general, patients with immune deficiency disorders such as diabetes, cancer, and kidney disease are at a greater risk for developing necrotizing fasciitis because of the compromised state of the immune system. Also, patients taking steroids for various different medical conditions should be aware of the elevated risk factor this causes.

The primary method of transfer for bacteria causing necrotizing fasciitis is through the skin. Therefore, open wounds are of particular concern for transmission. Wounds such as bedsores and postsurgical incisions also increase a patient's risk for developing necrotizing fasciitis.

Rapid, aggressive medical treatment, specifically, antibiotic therapy and surgical debridement, is imperative. Antibiotics may include penicillin, an aminoglycoside or third-generation cephalosporin, and clindamycin or metronidazole. Analgesics are employed for pain control. During surgical debridement, dead tissue is stripped away. After surgery, patients are rigorously monitored for continued infection, shock, or other complications.

Many doctors believe that multiple antibiotics should be used at the same time to protect the patient from methicillin-resistant staphylococcus aureus (MRSA), as well as infections with anaerobic bacteria, and polymicrobic infections. Treatments such as insertion of a breathing tube, intravenous administration of fluids, and drugs to support the cardiovascular system may be required. If available, hyperbaric oxygen therapy has also be used.

Necrotizing fasciitis has a fatality rate of about 25%. Diabetes, arteriosclerosis, immunosuppression, kidney disease, malnutrition, and obesity are connected with a poor prognosis. Older individuals and intravenous drug users may also be at higher risk. The infection site also has a role. Survivors may require plastic surgery and may have to contend with permanent physical disability and psychological adjustment.

Necrotizing fasciitis, which occurs very rarely, cannot be definitively prevented. The best ways to lower the risk of contracting necrotizing fasciitis are:

The news of flesh-eating bacteria incidents have heightened the awareness of the general public regarding their susceptibility to being infected with the deadly disease. Most cases of flesh-eating bacteria have been sporadic rather than associated with large outbreaks. But there are increasingly more reports from clinical centers. The disease is difficult to treat and immediate treatment is needed to prevent death. For this reason, the public health system's ability to contain a flesh-eating bacteria epidemic or similar outbreak remains somewhat questionable to many.

The CDC tracks specific infections in the United States, including necrotizing fasciitis caused by group A strep, with a special system called Active Bacterial Core surveillance (ABCs). ABCs is an important part of CDC Emerging Infections Programs network (EIP), a collaboration among CDC, state health departments, and universities. By sharing this kind of information in a timely way, public health professionals can look for trends in rising cases. Each year in the United States, there are about 650-800 cases of necrotizing fasciitis caused by group A strep; this is likely an underestimation as some cases are not reported. According to ABCs data, the number of annual infections does not appear to be rising.

Paul A. Johnson, EdM
Karl Finley