@ Yoga
Very unfortunate for your friend to have succumbed to NF - only around 500 cases a year in the UK.
I have included a link from the Health Protection Agency on NF in the UK for your information. In most cases, the route of infection is usually identified as a small cut or scratch, or a skin lesion like a blister. The causative organism will be identified, but one of the more virulent is Streptococcus A, which can befound on the skin. Intruducing skin flora into the body is one of the recognised dangers of a venepuncture or immunization, which is why normal practice is to clean the skin with an alcohol swab or similar prior to the procedure. It will be interesting to hear any additional details, as and when you hear them.
http://www.hpa.org.uk/Topics/InfectiousDiseases/InfectionsAZ/NecrotisingFasciitis/GeneralInformationNecrotisingFasciitis/