Having The Flu Many Times
There are many reasons you don’t want to catch the flu and the flu increasing the chances of diabetes is one of those reasons. In fact, the flu can potentially cause type 1 diabetes which is the worst type as you cannot produce any insulin on your own at all. Because type 1 diabetes is autoimmune, the flu can cause inflammatory cells to come out and ruin the cells that produce insulin which is how it can happen.
Even though this has been shown to happen in animals, more research needs to be done to see if this happens to humans. But assume that the risk is there and do what you can to stay healthy.