Necrotising fasciitis: symptoms, causes, treatment and why speed matters

The NHS says symptoms can develop within hours or over a few days. The infection usually happens near a cut or wound, but sometimes there is no obvious damage to the skin in the affected area.

• Intense pain or loss of feeling, often much worse than you would expect from a cut or wound.

• Redness and swelling of the skin around the area. Redness may be harder to see on black or brown skin.

• Flu-like symptoms such as a high temperature, headache and tiredness.

• Later: vomiting, diarrhoea, confusion, and blisters or black, purple or grey blotches on the skin, which may be less obvious on black or brown skin.

The NHS says bacteria can enter the body through cuts, scratches, sores or other wounds that break the skin, burns and scalds, insect bites, surgery, injecting drugs and urinary tract infections. You may be at greater risk if you have diabetes or a weakened immune system. Most people who get a cut or bite never develop this infection.

The NHS says to call 999 or go to A&E if you have a cut, wound or red or swollen area of skin that is much more painful than you would expect, or if you have such an area and develop symptoms like a high temperature, headache, tiredness and muscle aches. It also lists sudden confusion, dizziness or a pounding, fast, fluttering or missing heartbeat, and black, purple or grey blotches or blisters near a wound or red area.

It adds that you should not drive yourself to A&E: ask someone to drive you or call 999 for an ambulance, and bring any medicines you take. If you are not sure what to do, NHS 111 can advise on the right place to get help, although severe pain with feeling very unwell should not wait.

Necrotising fasciitis, sometimes called the flesh-eating disease, is an infection caused by bacteria getting into the deep layers of the skin and the tissue below. The NHS stresses that it is very rare. It spreads quickly through these tissues, and the speed is what makes it dangerous: it gets worse quickly and can be fatal if it is not treated as soon as possible.

Because it is so rare, most skin infections, wounds and red, painful areas are not necrotising fasciitis. The reason to know about it is that the early signs can look like something much more common, and the response needs to be immediate when the picture does not fit.

The NHS notes that the symptoms can be similar to more common skin infections such as cellulitis. Cellulitis makes skin painful, hot and swollen and is usually treated with a course of antibiotic tablets, with most people recovering fully after 7 to 10 days, according to the NHS cellulitis page. The NHS necrotising fasciitis page highlights pain much worse than expected, flu-like symptoms, and later confusion, blisters or dark blotches as the features that should prompt emergency help.

The NHS cellulitis advice also says to call 999 or go to A&E if cellulitis comes with a very high temperature, fast heartbeat or breathing, purple patches, dizziness, confusion or cold, clammy skin, because these are signs of serious complications.

The NHS says treatment will usually include antibiotics and surgery to remove the damaged tissue. Severe infections can lead to sepsis, and the NHS sepsis page says sepsis is treated in hospital with antibiotics, oxygen and fluids given into a vein, sometimes in a specialist care unit where you can be closely monitored, and that recovery can take weeks or months.

The NHS says sometimes amputation of affected limbs is needed.

The NHS says that even after successful treatment there may be long-term changes in how your body looks and how you move or use the affected part. You may need further surgery and physiotherapy to help you recover. Emotional recovery matters as much as physical recovery after a sudden, frightening illness, and it is reasonable to ask the hospital team about psychological support and about who to contact if wounds or symptoms change after discharge.

The NHS pages we read describe necrotising fasciitis as an infection caused by bacteria getting into the deep layers of the skin through a break in the skin, a burn, a bite, surgery, injecting drugs or a urinary tract infection. They do not describe it as spreading between people in ordinary contact, and the NHS says it is very rare. The NHS does say you cannot catch cellulitis from another person.

UKHSA says group A Streptococcus, one of the bacteria that can cause severe skin and soft tissue infections, spreads by close contact, including respiratory particles and direct skin contact. If you are worried about close contact with someone who has had a severe infection, ask NHS 111 or your GP.

There is no fixed duration, because it is a rapidly progressive emergency rather than a self-limiting illness. The NHS says symptoms can develop quickly within hours or over a few days and that recovery after treatment can involve further surgery and physiotherapy. The NHS says recovery from sepsis, which severe infections can lead to, can take weeks or months.

Necrotising fasciitis is an emergency and care is given through NHS emergency departments and hospital surgical and critical care teams. There is no sensible role for waiting for a routine or private appointment: the NHS says it must be treated in hospital as soon as possible.

Afterwards, the NHS says you may need further surgery and physiotherapy to help you recover, and long-term changes in how your body looks and how you move or use the affected part. Rehabilitation and wound care are usually arranged by the hospital team.