ConditionInfections
Necrotizing Fasciitis (Flesh-Eating Disease)
Necrotizing fasciitis is a rare but life-threatening bacterial infection that spreads rapidly along the tissue layers beneath the skin, destroying fat, fascia and sometimes muscle. It often starts from a minor cut, surgical wound or blister. The key early warning sign is severe pain out of proportion to how the skin looks, with rapid spread, fever and feeling very unwell. It is a surgical emergency: survival depends on prompt surgery to remove dead tissue, IV antibiotics and intensive care.
Also called: Flesh-eating disease, necrotizing soft tissue infection, NSTI, necrotising fasciitis
At a glance
- What it is
- A rapidly spreading infection of the deep soft tissues that kills tissue.
- Common bacteria
- Group A Streptococcus, mixed bacteria including anaerobes, Staphylococcus aureus (including MRSA), Vibrio vulnificus from seawater.
- Early signs
- Severe pain beyond what the wound suggests, swelling, warmth, fever, rapid worsening.
- Late signs
- Blisters, gray or black skin, numbness, crackling under the skin, shock.
- Treatment
- Emergency surgery, IV antibiotics, intensive care. Delays raise the death rate.
When to get help
Call 911 or go to the ER
- Severe pain, swelling or redness around a wound or in a limb that is spreading quickly, with fever: go to the ER or call 911
- Pain that seems far worse than the skin looks, especially with feeling very unwell
- Skin that turns purple, gray or black, develops blisters, becomes numb, or crackles when pressed
- Confusion, dizziness, a racing heart or low blood pressure with a skin infection
See a doctor within a day or two
- A red, warm, painful area that is spreading over hours despite antibiotics
- A wound infection in someone with diabetes, a weakened immune system or after recent surgery
Book a routine appointment
- Prevent infections: clean all wounds, keep them covered, and avoid hot tubs, pools and seawater with open wounds
What happens in necrotizing fasciitis
Bacteria enter through a break in the skin, such as a cut, scrape, insect bite, injection site, burn or surgical wound, and sometimes with no visible wound. They spread along the fascia, the connective tissue sheet that surrounds muscles. Toxins destroy tissue and blood vessels, cutting off blood flow, so antibiotics alone cannot reach the infected area well. The infection can spread several centimeters an hour and cause septic shock and organ failure.
Types
| Type | Bacteria | Typical setting |
|---|---|---|
| Type 1 (polymicrobial) | Mixed aerobes and anaerobes | Older adults, diabetes, after abdominal surgery, Fournier gangrene of the genitals |
| Type 2 (monomicrobial) | Group A Streptococcus, sometimes S. aureus | Healthy people of any age, limbs, after minor injury |
| Type 3 | Vibrio vulnificus or Aeromonas | Seawater or raw shellfish exposure, liver disease |
| Clostridial | Clostridium species | Gas gangrene after deep wounds |
Risk factors
- diabetes
- weakened immune system, cancer, chemotherapy or steroids
- chronic kidney or liver disease
- obesity and peripheral vascular disease
- recent surgery, injury or childbirth
- injecting drug use
- chickenpox lesions in children
- alcohol use disorder
Many cases, particularly from group A strep, occur in previously healthy people.
Symptoms
Early (first 24 to 48 hours)
- severe pain out of proportion to the visible skin changes
- redness, warmth and swelling that spreads quickly, often looking like cellulitis
- tenderness beyond the visible redness
- fever, chills, nausea, feeling very ill
Later
- swelling with tense, shiny skin
- blisters filled with dark fluid
- skin turning purple, gray or black
- numbness as nerves are destroyed, so pain may paradoxically decrease
- crackling under the skin (gas)
- foul-smelling discharge
Systemic signs
- fast heart rate, low blood pressure, confusion and reduced urine: sepsis and septic shock
- toxic shock syndrome with group A strep
Necrotizing fasciitis vs cellulitis
| Cellulitis | Necrotizing fasciitis | |
|---|---|---|
| Pain | Proportional to redness | Severe, out of proportion |
| Spread | Over days | Over hours |
| Skin | Red, warm | Later blisters, gray or black, numb |
| Response to antibiotics | Improves | Worsens despite antibiotics |
| General illness | Mild to moderate | Severe, often septic |
Diagnosis
Necrotizing fasciitis is a clinical diagnosis. Surgery should not be delayed for tests when suspicion is high.
- blood tests: very high or low white cell count, high CRP, low sodium, raised creatinine and lactate. Scoring systems such as LRINEC can support suspicion but cannot rule it out
- CT or MRI: may show gas or fluid along the fascia, if the patient is stable
- surgical exploration: the definitive test. Surgeons find gray, dead fascia that separates easily, with thin "dishwater" fluid and no bleeding
Treatment
- emergency surgery to remove all dead tissue (debridement), usually repeated every 24 to 48 hours until clean. Amputation may be necessary to save life
- broad-spectrum IV antibiotics, typically including a drug such as clindamycin or linezolid that suppresses toxin production, adjusted to culture results
- intensive care with IV fluids, blood pressure support and organ support
- IV immunoglobulin sometimes for streptococcal toxic shock
- hyperbaric oxygen in some centers
- reconstructive surgery, skin grafts and long rehabilitation afterward
Outlook
Necrotizing fasciitis has a significant death rate, often reported around 1 in 5, higher with delayed surgery, septic shock, older age and comorbidities. Survivors often face multiple operations, scarring, possible amputation and long recovery, and benefit from physical therapy and psychological support.
Prevention
- clean all cuts, scrapes and wounds with soap and water and keep them covered
- see a doctor for wounds that are deep, dirty or show signs of infection
- avoid hot tubs, swimming pools and natural water, especially seawater, while you have open wounds
- if you have liver disease or a weakened immune system, avoid raw oysters
- control diabetes and keep up with foot care
Frequently asked questions
What are the early signs of necrotizing fasciitis?
Early signs are severe pain that seems far worse than the wound or redness looks, rapidly spreading redness, swelling and warmth, plus fever and feeling very ill. Within hours to days, blisters, dark skin and numbness can develop. Seek emergency care immediately.
What causes necrotizing fasciitis?
It is caused by bacteria, most often group A Streptococcus or a mix of bacteria including anaerobes. Staphylococcus aureus and Vibrio vulnificus from seawater are other causes. Bacteria usually enter through a cut, scrape, burn, bite or surgical wound.
Who is at risk of flesh-eating disease?
People with diabetes, weakened immunity, kidney or liver disease, obesity, recent surgery or injury, and injecting drug users are at higher risk. However, healthy people can also be affected, especially by group A strep infections.
How is necrotizing fasciitis treated?
It is treated with emergency surgery to remove dead and infected tissue, strong IV antibiotics and intensive care support. Repeat operations are often needed. Some patients require amputation. Speed of treatment is critical to survival.
Can you survive necrotizing fasciitis?
Yes. Most patients survive with prompt surgery and antibiotics, although the death rate is significant, around 1 in 5 in many reports. Survival is best when the infection is recognized early and treated immediately. Recovery can take months.
Sources
This guide was written from current patient and clinical guidance, including:
- CDC: Necrotizing fasciitis - a rare disease, especially for the healthy
- Infectious Diseases Society of America: Practice guidelines for skin and soft tissue infections (2014)
- World Society of Emergency Surgery: Guidelines for necrotizing soft tissue infections (2018)
- MedlinePlus: Necrotizing soft tissue infection
- NHS: Necrotising fasciitis