Wei Chen did not need to think too deeply about this. The Great Stink of London incident was something he could use as a reference.
It was said that because of the outdated sewer system, the messed up waste management, and many other factors, the Thames River turned into one giant, stinking open sewer. It smelled so horrible that the Parliament of that time was forced to fix it. Even the leisure cruise of the queen had to be canceled.
(Author Note: Great Stink of London - 1858: London's outdated sewer system dumped waste directly into the River Thames, causing a massive sanitation crisis during a hot summer. The incident did not cause massive deaths from outbreaks, even though people at that time feared it might. In the end, it was simply 'Stink as hell'.)
Now, imagine that incident multiplied by one hundred, or maybe one thousand, and add bubonic plague or cholera into the mix, since the cities in this world are the size of entire countries.
