Diabetes may be triggered by flu virus, say researchers. In diabetes, cells do not take up sugar from the blood. This can happen because cells have lost sensitivity to the hormone insulin, which leads to type 2 diabetes.
Linked to diet and lifestyle, this form of the disease is rapidly becoming more common throughout the globe.
Another cause of diabetes is when the immune system destroys the pancreatic cells that produce insulin.
Since the 1970s, researchers have suspected that viruses may provide this trigger, as type 1 diabetes often sets in suddenly after an infection.
Enteroviruses and rotaviruses were both implicated; something about these infections confuses the immune system enough to make it attack the pancreas.
"The great thing is that even if flu only causes a few per cent of type 1 diabetes cases, we can vaccinate and prevent flu in people who are genetically predisposed, and that can have a real impact," Ilaria Capua, of the World Organisation for Animal Health reference lab for bird flu in Legnaro, Italy, said.
There are 65,000 new cases of type 1 diabetes worldwide annually, and that figure is growing by 3 to 5 percent every year.
The link between diabetes and flu adds to growing evidence that many diseases considered non-infectious are actually caused by infection - and can therefore spread.
The study has been published in the Journal of Virology.