Most of the negative consequences of the curse happened because God relaxed his protective grip on the world. He didn't specifically make diseases. They came about because God was no longer protecting the world from stuff like that. He didn't make diseases happen. He LET them happen as a result of the curse.
When Adam and Eve chose to disobey God they were basically proclaiming "We want to do this our way. We can become gods ourselves. We don't need your protection ".
So, the last 6,000 years God has let man do things his way and humanity has suffered huge negative consequences because of it.