Because Emergent Diseases are such an important reason behind why I have written this, I'm including a few links to some of the major sources on the topic. Put it this way, antibiotics are falling behind in the ancient and endless war against disease. That combined with human population numbers and modern travel, could in normal circumstances lead to worse problems from disease than humans had before antibiotics. For now, our only chance will be improved sanitaty practices. That will not prevent the inevitable pandemics though. We will need to be socially and morally prepared for those.
I also included this because I have been challenged on this point, though it is simply common knowledge in biology and medicine. Shortly after antibiotics were created, antibiotic resistence was recognised in bacteria.
The changes in human ecology, the changes in the energetic equation of survival, are going to require better immune systems and other genetic adaptations for humans to survive if we want to keep a civilization and technology. The ongoing genetic load is going to make diseases worse. Diseases will attack any weak link in human phisiology.
This is a short list. I'll tune this up in the future, because most of these are rather dry, conservative descriptions. I see that there is far more on the topic than when I last looked a couple years ago. It's not a surprise. The problem is obvious and great.