Necrotising fasciitis is a bacterial infection that attacks the soft tissue and fascia that bind together muscles and organs.
The bacteria usually enter via a cut, blister or small injury, but sometimes there is no visible entry point. The disorder is rare, but often fatal.
Skin turns deep violet with blisters, as the underlying tissue "necrotises" or dies. If untreated, death can follow rapidly. Vibrio vulnificus and group A Streptococcus are common bacterial causes.
Anyone can get it, but people with weakened immune systems or skin lesions and those with cirrhosis, diabetes or renal failure are at more risk.
There were 69 cases in Hong Kong between 2007 and 2011, with 59 of those occurring in the summer months, between June and October.There have been 11 cases so far this year.
It is treated by intravenous antibiotics followed by surgery and, in some cases, amputation.
The Health Department urges the public to avoid exposing open wounds or broken skin to seawater; avoid contact with dirty water in wet markets; wear protective clothing when handling raw seafood; clean and cover wounds; and cook seafood thoroughly.
If symptoms and signs of infection such as redness, pain and swelling occur, people should seek prompt medical advice.