Bad flu season linked to diabetes spike
A particularly bad flu season in Australia has triggered a sharp rise in the diagnosis of type 1 diabetes, say experts.
They say influenza could have been the final straw for children with already compromised insulin production systems.
Dr Neville Howard of the Children's Hospital at Westmead in Sydney reports his hospital has diagnosed more than twice as many children than usual with type 1 diabetes.
"Every year in the winter there's more children getting diabetes than at any other time of the year," says Howard. "However, this year there's a mini epidemic occurring."
Type 1 diabetes generally develops in childhood and is where the body's immune system attacks the insulin producing cells of the pancreas.
If left untreated it can cause uncontrolled blood glucose and ketone levels, called ketoacidosis, that leads to a coma.
Howard says his hospital would normally see six or seven children a month at this time of year, with only the occasional case of life-threatening ketoacidosis.
But this month the hospital diagnosed 17 cases and six of these required intensive care for diabetic ketoacidosis.
Howard says Newcastle experienced a similar mini-epidemic, also with more severe cases than usual.
He thinks cases have been more severe because some parents and doctors have missed the symptoms, assuming they were from the flu.
Diabetes Australia New South Wales this week issued a warning to parents and doctors to look out for symptoms, especially increased thirst, urination and weight loss.
Anecdotal reports suggest there have also been increased rates of type 1 diabetes in other areas of Australia.
But it is too early to say if this flu season will increase the incidence of type 1 cases in Australia for 2007 beyond what would be expected.
Scientists don't know what causes type 1 diabetes but believe it is triggered by environmental factors, including viruses, in people who are genetically susceptible.
So far, influenza A specifically has not been shown to trigger type 1 diabetes but other viruses like enteroviruses, which affect the gut immune system, have.
Scientists think that such viruses and other environmental factors trigger the autoimmune reaction repeatedly over many years.
Each episode reduces the number of insulin producing cells until finally there are too few left and the child develops type 1 diabetes.
"You need to destroy about 90% of the insulin producing cells before diabetes develops," says Professor Don Chisholm, a diabetes researcher at Sydney's Garvan Institute.
"These people were probably well down the track to developing type 1 diabetes," he says. "And the flu illness has acted as the final straw that broke the camel's back."
While the virus could have stimulated the autoimmune destruction of insulin producing cells, Chisholm says it could also have triggered insulin resistance, which reduces the body's response to insulin.
Chisholm says viral diseases could trigger other autoimmune diseases but the effect would be less noticeable.
Test results in the wings
Howard says he is yet to get test results back to confirm his suspicions that influenza A played a role in the current peak of type 1 diabetes cases.
He says a whole range of environmental factors that affect the immune system are being investigated as possible contributing factors.
Howard is investigating whether cows' milk help children to develop the condition.
Type 1 diabetes affects about 130,000 Australians and the incidence is increasing by about 3% a year.
One popular theory for the increase is the 'hygiene hypothesis', which suggests excessive cleanliness results in an over-reactive immune system that ends up attacking the body's own tissue.