Stop Medieval Diseases with a Medieval Wall
Like superstitious dark age types, leftists insist on blaming the typhus outbreaks on global warming, caused by an angry 'Mother Earth' rather than on the very real spread of disease by people. Instead of preventing the spread of disease, they insist that we must repent for our crimes against the environment, and recycle more, and then the earth will cool and the typhus outbreak will stop.
The legalization of illegal migration and homelessness, is leading to a new wave of disease outbreaks. If you want to stop a medieval disease, you might want to start with a medieval wall.