Some 709 people in North Korea - which claims it is "totally free" of virus cases - have been tested, says the World Health Organisation.
Of those, 11 are said to be foreigners and 698 locals, Dr Edwin Salvador, the WHO representative to North Korea told Reuters news agency.
North Korea has a population of about 25 million - so this means a tiny fraction of the population would have been tested.
To put these numbers into perspective, neighbouring South Korea, with a population of 51 million, has tested 486,003 people so far.
A North Korea analyst told the BBC it was unlikely that there were no cases a country that borders China and South Korea.
Especially with China, Oliver Hothman said, "given the amount of cross border trade and the economic relationship I really don't see how its possible they could have prevented it".
However, he added, a full scale outbreak in North Korea was unlikely.