Tiny, toxic and taking over

Dr Thomas Proft, senior lecturer in microbiology and infectious diseases, molecular medicine and pathology, at the School of Medical Sciences, Auckland University, is spearheading research to try to combat the spread of streptococcus. Photo by The New Zealand.

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 quickly and can be fatal.

If the bacteria get into the blood it can lead to toxic shock syndrome, which can rapidly result in stupor, coma, multi-organ failure and death.

Fortunately, it's quite rare.

Unfortunately, in a relatively short space of time, there's been a fivefold 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," Assoc Prof Michael Baker, of the Department of Public Health at Otago University, says.

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

Prof 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 to 2006, showed there was, on average, a 21% chance of dying from the disease.

Prof Baker doesn't have an explanation, but says whenever there is a change in incidence a trinity of factors - host, organism and environment - comes 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 about 40% more likely to get the disease, Maori 85% and Pacific people about 135%.

Those aged under 10 are least likely to get the disease, and those aged 70 and above have 20 times more risk.

Prof 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."

The research also compared the incidence of the far more common cellulitis - a skin inflammation caused by bacteria which, if it isn't treated, can develop into necrotising fasciitis.

In 2006 there were about 7000 discharges from our hospitals with cellulitis - about 100 times more than necrotising fasciitis.

Cellulitis is also hardly ever fatal, but it too is on the increase - its incidence almost doubled between 1990 and 2006.

"We need far more regular scrutiny because this increase has really gone under the radar for many years," Prof Baker says.

Middlemore Hospital has also done some research into necrotising fasciitis, looking retrospectively at 82 patients between 2000 and 2006.

Specialists Dr David Holland and Dr Mitzi Nisbet found mortality for the disease was around 30%.

"We found it was more common in Pacific Islanders," says Dr Holland - not unexpected because the hospital is in an area with a large Pacific Island population.

Chronic renal failure and gout were independent predictors of mortality.

"Patients with these conditions and sepsis especially need early assessment, aggressive triaging and rapid intervention," says Dr Holland.

Chief adviser of Pacific Health Dr Api Talemaitoga says the Ministry of Health commissioned the report to address concerns about an apparent increase in the disease.

The concerns stemmed from a cluster of cases in 2006, when four young Samoan men were admitted to hospital with severe infections - including necrotising fasciitis that nearly killed one of the victims - after receiving traditional Samoan tattoos.

There had also been similar cases in 2002.