So far as I am aware God has promised to rid the World of evil, diseases etc. It hasn't happened yet. Indeed, on the diseases front the current score is God 0, Mankind 2 (and 2 more coming up). The only reason that we've not chalked up a third in Polio is because some extreme religious nutjobs in Africa are convinced that the Polio Vaccine is a Western plot to poison their children and make the men infertile or some such nonsense.
It's not always true, of course, but it does sometimes seem that the more you wait for your God to solve the problems of this World, the less inclined you are to fix them yourself. So allow me to offer up a reverse Pascal's Wager:
1) There is no God, in which case the only people who can combat evil, suffering, etc., are ourselves, and if we don't then no-one else will. Therefore, we should worry about disease and suffering and we should try our hardest to reduce and fight them.
2) There is a God, and at some indeterminate point in the future He will effect a sweeping change that in one stroke will create Paradise (possibly only for the chosen). In the meantime, however, we and many others will suffer from said diseases, so it makes sense to try to alleviate that suffering. After all, isn't that the sort of Goodly life that is valued?
So either way, the best bet is to stop waiting for God to fix the world and do it ourselves. Can't hurt.