A subterranean hospital known as the Cave and long the destination for war wounded is now filled with casualties of the earthquake — both alive and dead.

A photograph released by the Syrian American Medical Society showing Abdul Haseeb, 3, being brought to Al Atarib hospital after spending 36 hours buried under rubble.

Dr. Nehad Abdulmajeed thought he had seen the worst human suffering of his career as a surgeon in Syria. In 2016, he survived the siege of Aleppo, which left thousands dead or crippled in the midst of a civil war.

After the city fell to government forces, Dr. Abdulmajeed retreated to a town called Al Atarib, in the country’s northwest, where he worked in a hospital dug deep underground to protect it from relentless Russian and Syrian bombardments.

“Our hospital has always been filled with tragedy,” he said in a phone interview from his operating room. But the carnage he and his staff have seen this week, from an entirely different enemy, was of a scope he had never encountered.

Hundreds of casualties from Monday’s earthquake, which was centered nearby across the border with Turkey, have arrived this week at his hospital from the Al Atarib region, and many were already dead when they reached the hospital. Staff members say they had counted 148 bodies at the hospital since Monday.