I cannot explain every thing. I am not a doctor or a medical expert. However, many times things can be used multiple ways. Water is important to drink, without it you will die. Yet too much of it can kill you, especially if you swim in a lake. The water does good and bad. Why did God create water, if it downs children? The answer is not that simple. I do believe everything is created by God, but it has been corrupted my Man, the fall (sin entering the world), and Satan. I think some things are God's opportunity to give us chances to help and aid one another. I think some things are the result of Satan, not God. (The biblical story of Job is an interesting example of a man tempted by the devil.) Many of the diseases that effect children have now been cured. Medicine has made remarkable progress in the last 200 years. That said, there are still more diseases for us to cure. That said some things may happen for no reason. They just happen.