This is the disease--basically internal moral rot and decay--that destroys civilizations. It's decadence. Whether or not it can be reversed, once the moral rot and decay have established themselves, nobody knows. President Trump thinks it can be.
The disease is contagious. It can infect the rest of the USA. Until a solution can be found, these highly infected places should be quarantined.
Simple: Quit feeding the homeless. No food, no poop created.