Yup I also believe in that possibility but I just have this lingering doubt as to how most East Asian countries have relatively moderate pandemic infection rates.While I'm myself not too sure of this. I will try to take a wild dig here at the situation
All these have low pop density compared to rest of the country.
The region is still isolated from rest of the country
Houses are more spaced out.
No international airport so lower chance of infection.
Not much road and rail connectivity either.
Diet is definitely not a strong forcing factor as Italy which has the famed Mediterranean diet got heavily infected with Covid 19.
