The U.N. commission told of a medical emergency worker in Aleppo who was shot by a sniper in early September “while in full medical uniform and holding a medical bag with a Red Crescent.” An ambulance that was evacuating wounded rebels was hit five times by sniper fire.

The Syrian Network for Human Rights says it’s documented more than 1,400 cases of injured people – fighters and civilians – who went into hospitals and were killed.

International agencies, among them the Geneva-based International Committee of the Red Cross, are able to deliver medical supplies to hospitals in government-held areas, but they’re delayed for weeks, often months, when they attempt to deliver supplies to opposition-held areas.

That’s taken a toll not just on treatment of the wounded, but also on those who need care for other medical conditions.

“The situation’s catastrophic everywhere,” said Dr. Mego Terzian, the emergency operations manager for the French-based Medecins sans Frontieres, or Doctors without Borders, the only international aid organization that’s openly operating in rebel-held areas. “There is no capacity for blood transfusions. For chronic problems like asthma and cardiovascular illnesses, there is almost zero treatment available.”

Terzian said the health system had declined in stages after what began as a government crackdown on opposition demonstrations devolved into open warfare.

“After the opposition armed itself, the regime started to arrest medical personnel everywhere, accusing them of treating terrorist groups. Then it started to bomb a lot of health structures,” he told McClatchy.

Doctors without Borders views the collapse of the health care system as a reason that more Syrians are fleeing abroad.

"Last year, the focus was around the wounded and direct victims of violence. Now there is a more general collapse of the health system,” said Bruno Jochum, the organization’s director.