The World Health Organisation said fewer than 1,000 people have been tested but a number of its citizens are in quarantine.
The reclusive country has reportedly sent the workers to the border to assist with "quarantine" operations.
Comments by defense secretary Mark Esper saying the US is ready to fight North Korea if needed were reported by Iran's state media channel PressTV.
In a mammoth seven-hour speech, Kim Jong Un appeared to suggest that nuclear diplomacy with the US could end.
North Korean leader Kim Jong Un supervised a parachuting drill of military sharpshooters and vowed to build an “invincible army,” displaying more defiance even as the United States and South Korea called off their own exercises to create space for nuclear diplomacy.
North Korea has reportedly fired two short-range ballistic missiles from a new rocket launcher in its latest weapons test.
The test, which saw two short-range ballistic missiles fired in to the sea, is the fifth round of tests in less than three weeks.
Noel Gallagher: “You take part in a democratic process - if you don’t like the outcome, go to North Korea."
North Korea has fired at least one unidentified projectile from the country’s western area, South Korea’s military has said.
Putin told Kim that Russia supports his efforts to normalise North Korea's relations with the United States.
North Korea has test-fired a new type of "tactical guided weapon", it has announced. Kim Jong Un observed the weapon being fired on Wednesday by the Academy of Defence Science, state-run Korean Central News Agency said. The test is North Korea’s first such test in nearly six months, but it is not clear exactly what kind of weapon has been tested.
Kim and Trump shook hands and smiled briefly in front of a row of their countries' flags at the Metropole hotel in the Vietnamese capital, Hanoi.
Donald Trump and Kim Jong-un are getting ready for their summit later this week in Vietnam.
President Donald Trump said a time and location for his second summit with North Korea's Kim Jong Un had been agreed upon and will be announced next week.
On Tuesday, intelligence officials broke with Trump in their assessments of the threats posed by North Korea and other nations.