TOKYO — In these days of infection and fear, a recent propaganda photo sums up the image North Korea wants to show the world, as well as its people: Soldiers with black surgical masks surround leader Kim Jong Un, ensconced in a leather overcoat and without a mask as he oversees a defiant military drill.

As a new and frightening virus closes in around it, North Korea presents itself as a fortress, tightening its borders as cadres of health officials stage a monumental disinfection and monitoring program.

That image of world-defying impregnability, however, may belie a brewing disaster.

North Korea, which has what experts call a horrendous medical infrastructure in the best of times, shares a porous, nearly 1,450-kilometer (900-mile) border with China, where the disease originated and has since rapidly spread around the world. The North’s government has also long considered public reports on infectious disease — or, for that matter, anything that could hurt the ruling elite — matters of state secrecy.

This has raised fears that North Korea, which claims zero infections, may be vastly unprepared for a virus that is testing much more developed countries across the globe — and even that infections could already be exploding within its borders.

“Unfortunately, the international community has no idea if the coronavirus is spreading inside North Korea,” said a recent report by Jessica Lee, an East Asia expert at the Quincy Institute for Responsible Statecraft, a think tank in Washington. “The fact that we know nothing about the level of infection or deaths within North Korea is extremely problematic and, left unchanged, could have serious public health implications.”