A Red Crescent aid worker inspects scattered medical supplies after an airstrike on a medical depot in the rebel-held Tariq al-Bab neighborhood of Aleppo, Syria, on April 30. (Abdalrhman Ismail/Reuters)

As a doctor in the war-ravaged hospitals of Aleppo, Rami Kalazi has long felt uneasy about his job. Many of his colleagues have been killed by airstrikes and snipers or snatched by suspected government thugs.

But the hardest part has not been treating the wounded as medical supplies run desperately low and warplanes bomb indiscriminately. It is the anguish over his family’s future, he said.

Even though Kalazi has vowed to press on with the perilous work, he increasingly fears what his wife, Seba, and their young son would do if he were killed.

An apparent Syrian government air raid that leveled Aleppo’s al-Quds hospital has compounded his agony. Among the more than 50 people killed in the attack was Mohammed Wasim Moaz, Kalazi’s friend and possibly the only pediatrician still working in the city’s opposition-controlled districts.

“You work in such a dangerous place for a long enough time, then your chances of dying increase. It’s even harder when you have a family, when people depend on you,” said Kalazi, 30, a neurosurgeon from Aleppo who is among the few dozen doctors left to treat the roughly 250,000 residents living in the rebel-held areas of the city.

Kalazi’s struggle illustrates the immense pressure bearing down on medical professionals who work in Syria and, in particular, Aleppo, the country’s largest city before civil war decimated much of it.

Like many doctors who refuse to leave Syria, Kalazi sees his work in his home town as important for supporting the revolt against President Bashar ­al-Assad.­ But the conflict, now in its sixth year, has worn Kalazi down as it takes an apocalyptic toll on the country.

Before the civil war, Syrians had by regional standards a relatively well-functioning health sector. Now, many of the country’s hospitals lie in ruins while scores of doctors, nurses and other medical staff have been killed or fled abroad because of the fighting, which has left more than 250,000 people dead and displaced millions.

Warring parties on both sides of the conflict have frequently and deliberately attacked medical professionals, rights groups and aid workers say. But they accuse the Syrian government and its allies — notably Russia, which is carrying out airstrikes against rebels — of systematically targeting doctors and hospitals in rebel areas.

At least 664 medical workers, including doctors and nurses, have been killed by Syria’s government, according to a report by Physicians for Human Rights, which also attributed at least 288 attacks on medical facilities to pro-Assad forces. The attacks have worsened the country’s dire humanitarian crisis.

“These attacks lead us to believe that there is a deliberate strategy not only to target doctors and medical facilities, but just about anything that supports day-to-day life,” said Sam Taylor, a communications coordinator on Syria issues for Doctors Without Borders. The medical-aid group had supported al-Quds hospital.

Ahmad Tarakji, president of the Syrian American Medical Society, said the Aleppo area now has about one doctor per 10,000 residents. And, he said, it has about 300 available hospital beds and struggles with acute shortages of medicine, causing preventable deaths, including dozens of children who recently succumbed to complications from bronchitis.

Statistics on the government-controlled part of Aleppo are not available, but rebels also have targeted medical facilities. Days after the bombing of al-Quds hospital, opposition shelling of the government side of the city struck a hospital and a maternity clinic, killing at least three women.

Kalazi, who works in the city’s al-Suhor hospital, cited those issues and chronic electricity outages as major problems.

The most ominous threat, he said, comes from above.

His hospital has been hit by airstrikes multiple times, he said. Miraculously, though, the building has held together enough to allow a small staff of doctors and nurses to continue working there.

Kalazi, in particular, dreads barrel bombs. Dropped by plane or helicopter, the oil drums filled with explosives and metal shrapnel sound as if they are tearing through the air when falling. The effect is literally earthshaking, he said.

“You hear this horrible sound, and then you freeze up because there is nowhere safe to go,” Kalazi said. “Suddenly, everything shakes like an earthquake, the lights go off. Everything is covered in dust. Then you spend your time searching through the debris to see if your colleagues are still alive.”

Kalazi described seemingly endless streams of casualties rolling into his operating room over the years, many of them dead on arrival. Boys as young as his son, 1-year-old Ahmed. Pregnant women. Entire families.

“I’ll never forget this family that was brought to the hospital after the regime bombed their home,” he said. “There were seven kids and their parents. They were covered in dust. I remember seeing a baby, 3 months old, in his small clothes covered in dust. I tried desperately to revive them. They all died except for one little girl.”

A year ago, a bomb struck Kalazi’s family home, a short walk from the hospital. Seba and Ahmed were in the kitchen when the bomb hit but managed to emerge unscathed, even though their house was destroyed.

“The furniture was shredded. The ceiling caved in. I still don’t know how they lived,” he said.

After that, Seba and Ahmed moved in with her parents in the nearby province of Idlib.

Kalazi met Seba at a peaceful anti-government rally in Aleppo back in 2011. As the initially unarmed revolt transformed into civil war, the violence against doctors worsened. Several of Kalazi’s physician friends in the city were arrested and killed in government detention, he said. Last year, another doctor friend was killed by shelling while walking to work.

Even though a partial nationwide cease-fire has recently reduced fighting in Aleppo, pro-government forces have been on the verge of totally encircling rebel areas.

Only one road connects opposition forces in the city to the outside. If captured by the government, Kalazi would be cut off from his family, whom he visits in Idlib for a week every month.

“When I go back to Aleppo, it feels like I’m saying goodbye to Seba for the last time,” he said. “If the regime gets that road and I’m there, I might never see her again.”