Why does the environment cause some diseases/viruses

There are numerous viruses, bacteria and other microbes that can make us sick. Yet people praise nature?

It's all related to evolution.
Environment and nature created us through evolution,and it's still working!
mutations are happening every day,and new types of viruses are being created.some of them are ok! but some of them make us and other animals sick.and also mutations are happening in bacterias,and practically,in every living organism.
Nature is not in our favor all the time!sometime it's against us.but we're part of it after all.