“We worry about these infections because of how quickly they can become serious,” says Luis A. Manrique, MD, FIDSA, an infectious disease physician at Northwestern Medicine. “Recognizing warning signs and seeking medical attention early can make a significant difference.”

Dr. Manrique breaks down what to know, including causes, signs and symptoms, diagnosis and treatment, as well as prevention.

What Is Necrotizing Fasciitis?

Necrotizing fasciitis is a rapidly progressing infection that affects the deeper layers of skin and connective tissue. It often starts when bacteria enter the body through a small cut, scrape or other break in the skin.

Although it is rare in the United States, its severity makes awareness critical. The infection spreads quickly and can damage tissue, disrupt blood flow and lead to life-threatening complications if untreated.

What Causes Flesh-Eating Disease?

• Staphylococcus aureus, including Methicillin-resistant Staphylococcus aureus (MRSA)
• Clostridium species
• Vibrio vulnificus
• Combination of bacteria working together

Despite the nickname, these bacteria do not “eat” flesh. Instead, they release toxins that destroy tissue beneath the skin.

The infection typically begins when bacteria enter through:

• Minor cuts or scrapes
• Insect bites
• Burns
• Surgical wounds
• Injection sites
• Chronic wounds, such as diabetic foot ulcers
• Puncture wounds

How Serious Are Flesh-Eating Bacterial Infections?

These infections are rare but can be severe. If not treated quickly, the infection can lead to death.

At the same time, invasive group A streptococcus infections, which can include flesh-eating infections, have increased in recent years, making awareness especially important.

Who Is Most at Risk?

While anyone can develop necrotizing fasciitis, certain factors increase susceptibility. These risk factors often involve underlying health conditions or situations that impair the body’s ability to fight infection.

People with a weakened immune system face a higher likelihood of infection and complications. Conditions that increase vulnerability include:

• Diabetes
• Chronic kidney disease
• Liver disease
• Cancer
• Peripheral vascular disease
• Obesity

These conditions can slow healing, reduce blood flow or limit immune response, creating an increased risk that bacteria will take hold and spread.

Signs and Symptoms To Watch For

In the early stages, one of the most important warning signs is severe pain that feels out of proportion to the appearance of the skin.

Other symptoms may include:

• Rapidly spreading redness or swelling
• Severe tenderness
• Fever or chills
• Skin discoloration (purple, gray or black)
• Blisters or open sores
• Numbness in the affected area
• Drainage with foul odor

As the infection progresses, it can enter the bloodstream and cause symptoms of sepsis, such as:

• Confusion
• Rapid heart rate
• Low blood pressure
• Cold or clammy skin
• Difficulty breathing

When Should You Seek Care?

If you notice rapidly worsening pain, swelling, redness or discoloration around a wound, fever with skin changes or any of the symptoms of sepsis, seek medical attention immediately. Do not wait to see if symptoms improve.

One of the biggest challenges with necrotizing fasciitis is how quickly it evolves. What seems like a minor issue can escalate within 24 to 48 hours. Early intervention dramatically improves outcomes.

“Patients often think they have a routine skin infection early on,” says Dr. Manrique. “The problem is these infections can sometimes progress dramatically in a short period of time.”

How Is It Diagnosed?

Diagnosing necrotizing fasciitis can be challenging, especially in the early stages when symptoms overlap with less serious infections.

Doctors rely on several tools to evaluate the condition:

• Physical examination
• Blood tests
• Imaging, such as CT or MRI scans
• Surgical, exploration

In many cases, the diagnosis is confirmed during surgery.

How Is It Treated?

Treatment for necrotizing fasciitis is aggressive and typically involves multiple approaches at once. A coordinated medical team works quickly to stop the infection and stabilize the patient.

A treatment plan may include:

• Emergency surgery to remove infected and dead tissue
• IV antibiotics to treat the infection
• Critical care support, often in an intensive care unit (ICU)

Multiple surgeries may be needed depending on how the infection responds to treatment.

What Complications Can Occur?

Without early treatment, necrotizing fasciitis can lead to severe complications. As the infection spreads, it can damage multiple organ systems.

Possible outcomes include:

• Sepsis and septic shock
• Organ failure
• Loss of limbs (amputation)
• Extensive tissue damage
• Death

People with underlying health conditions, such as chronic kidney disease or liver disease, may be more vulnerable to complications because their bodies are less able to respond to infection.

How To Reduce Your Risk

While these infections cannot always be prevented, simple steps can lower your risk:

• Clean wounds promptly with soap and running water. 
• Keep cuts covered until healed and monitor for changes.
• Wash your hands regularly.
• Avoid exposing open wounds to lakes, oceans or hot tubs.
• Manage chronic conditions, such as diabetes.
• Seek care if a wound worsens instead of improving.

What Does Recovery Look Like?

Recovery can be complex and may involve long-term care. Many people require multiple surgeries to fully remove damaged tissue. Some people may also need:

• Skin grafts
• Physical rehabilitation
• Ongoing wound care

The physical effects can be significant, including scarring or reduced mobility. Emotional recovery is also important, as some patients experience anxiety, depression or post-traumatic stress after such a serious illness.

Ultimately, early treatment is the most important factor in survival. If something doesn’t seem right, trust your instincts and seek medical attention right away.

 “Speed matters,” says Dr. Manrique. “The earlier we recognize these infections and start treatment, the better the chances for recovery.”