system
Given the following post, respond as if you're commenting on Reddit:
human
Is there any studies on how Covid has spread in North Korea? Has the country's isolation protected it? In what ways has it managed to spread?
gpt
Studies?  Who do you think would perform these studies?

North Korea always limited travel across it's border.  They shut it down entirely in January of 2020 and it hasn't been re-opened since.  They even had major success in shutting down the black market smuggling, or so it's been told.

Your only source for news is the North Korean government.  

Officially there are zero cases in North Korea.

Unofficially a sate of emergency was declared in Kaesong City.  The government propaganda machine started reporting that a South Korean defector may have been found with the virus in this city, then the propaganda machine went dark and Kaesong City was never mentioned again.

As of January 8, North Korea has sent samples from 13,529 people to be tested in South Korea.  So far all tests have come back negative.  Make of that what you will.

There's no WHO members, or Red Cross members, or any outside organization left in the country, so the only source of any information is the government.