Experts said that given North Korea’s limited testing capabilities, the numbers released so far probably represent a small fraction of the infections, which could lead to thousands of deaths in one of only two countries in the world without a COVID-19 vaccination campaign.

About 187,800 people are being treated in isolation after a fever of unidentified origin has “explosively spread nationwide” since late April, the official KCNA news agency reported.

Roughly 350,000 people have shown signs of that fever, including 18,000 who newly reported such symptoms on Thursday, KCNA said. About 162,200 have been treated, but it did not specify how many had tested positive for COVID-19.

At least six people with fever symptoms have died, with one of those cases confirmed to have contracted the Omicron variant of the virus, KCNA said.