I am aware that Rome’s population decreased. My reasoning is that a population that was larger and denser in the past is carrying around more parasites. Rome is

I am aware that Rome’s population decreased. My reasoning is that a population that was larger and denser in the past is carrying around more parasites. Rome is just one example. By 1492, Europe had many large cities and lots of travel between them, enormously more population and travel than the Americas. They had a more fertile environment for parasites.