When I see tv footage of rush hour in the world's most densly-populated cities..esp Tokyo, those underground railway herds of paasengers..I think that we can't go on like this.
However, this 2016 article sees consumption as the key.
http://www.bbc.co.uk/earth/story/20160311-how-many-people-can-our-planet-really-support
Because of the close proximity of people, the Japanese have lots of habits that could potentially limit the transmission of disease.
For example, they are not a society that likes contact, they bow instead of shake hands. Even couples out in public don't hold hands.
When you pay, there is a tray to place your money down and they will put the change back down for you to pick it up,
You can order sushi on these conveyor belt trains "trains", vending machines everywhere. A lot of things are automated.
They use Sooooooooo much plastic in packaging, everything is sealed.
Every big building have alcohol dispensers at the entrance..
There is also the culture of mask wearing when you feel ill so not to spread germs.
They moved the fish market to a new building last year because the old market had people and raw fish side by side. The new building you can't go to as a visitor, it is much cleaner.
There is also a habit that they think blowing your nose in public is bad manners, people will suck it back and swallow it.
The streets in general are so clean you can practically eat off of it. People don't litter, don't spit and don't walk and eat so there are no crumbs around, meaning less chance of rodents.