Dr Thomas Proft is spearheading research to try to combat the spread of streptococcus. Photo / Brett Phibbs

Dr Thomas Proft is spearheading research to try to combat the spread of streptococcus. Photo / Brett Phibbs

Necrotising fasciitis. Words you really don't want to hear when you turn up at hospital with a small cut or abrasion that's causing a preposterous amount of pain.

Recognised since the 18th century as phagedena, and also described as a variety of gangrenes - hospital, gas, Meleney's, Fournier's - necrotising fasciitis usually features in today's media reports alongside "flesh-eating bacteria".

Bacteria are involved but they don't eat anything, preferring instead to release toxins which kill human cells. That's the necrotising bit. While flesh dies, it's well below the skin's layers - the fibrous stuff that surrounds organs, muscle and bone - the fascia.

When necrotising fasciitis gets hold, it spreads very fast and can be fatal. If the bacteria get into the blood it can lead to toxic shock syndrome which can rapidly progress to stupor, coma, and multi-organ failure and death.

Fortunately, it's quite rare. Unfortunately, in a relatively short space of time, there's been a five-fold increase in its incidence. "We are now seeing around 80 necrotising fasciitis cases a year - a rate of two per 100,000 - compared with the early 90s when we had an average of 13 hospitalised cases a year," says associate professor Michael Baker of the Department of Public Health at Otago University.

"An extremely rare disease is now a far less rare disease."

Baker is co-author of a study, supported by the Ministry of Health, which took a wider look at the changing epidemiology of necrotising fasciitis and serious skin infections in New Zealand. National hospitalisation and mortality records, plus 300 patient files from 1990-2006, showed on average there was a 21 per cent chance of dying from the disease. Baker doesn't have an explanation but says whenever there is a change in incidence a trinity of factors - host, organism and environment - come into play.

"A possible change in the organism is probably one of the first hypotheses you're going to think about. These bugs that invade our bodies have the ability to surprise us. They can evolve very swiftly and they can become more virulent."

Males are around 40 per cent more likely to get the disease, Maori 85 per cent and Pacific people around 135 per cent. The lowest risk age group are under 10 years and those 70 and above have 20 times more risk.

Baker says ethnicity is often a marker for other things. "We know there are big socio-economic and health inequalities in these groups and this really does suggest basic health determinants are operating." Further analysis is needed to look at things such as housing conditions, income, access to medical care and nutrition. "We know a lot of these cases had other chronic illnesses such as diabetes which may predispose people to the disease but we haven't established those associations yet."