Common infections may be a trigger for diabetes in children and young adults, research suggests.
Diabetes is linked to health problems
Scientists analysed 25-years' worth of data on more than 4,000 young people in Yorkshire with type 1 diabetes.
The team from Leeds and Newcastle found clusters of unusually high numbers of cases among 10 to 19-year-olds in certain locations and at certain times.
This, they argue in the journal Diabetologia, suggests a common cause - such as an infection.
TYPE 1 DIABETES
About 250,000 cases in the UK
20,000 UK children aged under 15 have diabetes - most with type 1
Number of childhood cases has increased by 3% per year in the UK over the last 40 years
Peak age for diagnosis is 10-14 years old but is becoming younger with a steep rise in children under five
Nearly all people with type 1 diabetes are diagnosed by the time they are 40
There are about 250,000 people with type 1 diabetes in the UK, and the number of cases in children is rising by 3% each year.
It develops if the body is unable to produce any insulin to control levels of sugar in the blood, and usually emerges before the age of 40.
The researchers, from Newcastle and Leeds Universities and Leeds Teaching Hospitals NHS Trust, found that there were 6% to 7% more cases in the clusters they identified than could have been expected by chance.
The phenomenon was particularly pronounced in women and girls.
The pattern, which experts call "space-time clustering", is typical of conditions triggered by infections.
Conditions caused by more constant environmental factors produce clusters of cases in one place over a much longer time period.
It has previously been suggested that infections are linked to the development of type 1 diabetes in children who are genetically susceptible to certain environmental triggers.
Lead researcher Dr Richard McNally said: "This research brings us closer to understanding more about type 1 diabetes.
"However, it is just one piece in the jigsaw and much more research is needed before we can identify which infections may be to blame and thus inform advice on preventative measures.
"The condition is likely to be caused by an interplay of factors, of which infections are just one element."
Simon O'Neill, of the charity Diabetes UK, said: "We always suspected that common infections could be a trigger for type 1 diabetes in those who are already genetically susceptible.
"This research provides vital evidence in supporting this link.
"The fact that the number of cases of type 1 diabetes is rising by 3% each year cannot be explained by genetics alone.
"This research reinforces the idea that common infections and environmental factors also play a part."