Necrotizing fasciitis is a bacterial infection caused most commonly by the Streptococcus aureus (Strep A) bacterium. This is the same bacterium that causes common sore throat (strep throat) and impetigo, a skin infection. It also causes a tissue inflammation and infection called cellulitis. Necrotizing fasciitis, toxic shock syndrome and bloodstream infections are diseases that occur when the bacteria become invasive. One variety of Strep A is resistant to antibiotics and frequently causes death or disfigurement through scarring and amputation. It destroys soft tissue at the subcutaneous level, and often is coupled with toxic shock syndrome; both can be deadly alone, together they are even more potent. Most often the bacteria enters the body through an opening in the skin (a cut, abrasion etc). It is most commonly transferred by respiratory droplets or direct contact with secretions of someone carrying Strep A.
Necrotizing means death-causing, and that happens because the bacteria make a toxin and cause inflammation that blocks blood flow to tissue, causing it to die.
Five to thirty percent of the population carries Strep A at any given time usually with no symptoms. Seventy-five percent of the cases are misdiagnosed. A 1996 report of the US Centers for Disease Control estimates from 500 to 1500 cases per year of necrotizing fasciitis of which 20% die. In 1998, the US National Necrotizing Fasciitis Foundation estimates the figure to be higher (based on cases reported to measured against the general population with access to the Internet). Old people, children and people with weak immune systems are at greater risk for big complications from a Group A Strep infection.