Our family has a lot of diabetes in it and we have some close friends whose son also has type 1 diabetes. They have mentioned the virus thing. That has not been proven, though, it is still a theory as to the cause of type 1 diabetes. It's possible that the child catches a virus that attacks the pancreas causing to to stop producing insulin. Type 1 diabetes is in children when their pancreas stops producing insulin.
Type 1 diabetes: Causes - MayoClinic.com
Type 2 is typically in adults (can be in children) typically due to being overweight and when your body cannot properly use the insulin that it makes.
There is a new condition that doctors are beginning to see in children called Double Diabetes, due to the childhood obesity problem. It is when they have both types of diabetes at the same time.
Both types of diabetes can be hereditary, but isn't always. Diabetes is prevelant in our familly, but our friends whose son has it, don't have it.
Lisa