SEOUL—The challenge to contain the coronavirus looks particularly daunting in North Korea, one of the world’s poorest and most isolated countries.

North Korea was among the first countries last month to block the entry of foreign tourists, who come mostly from neighboring China, the source of the outbreak. It has since cut off trade with China, its main economic benefactor and ally, and limited diplomatic travel, according to North Korean state media and diplomats. The country hasn’t reported any cases of the deadly coronavirus.

...