ATMEH, SYRIA - A 4-month-old boy joined the ranks of Syria's tens of thousands of war wounded when a missile fired by Bashar Assad's air force slammed into his family home and shrapnel pierced his skull.

Fahed Darwish suffered brain damage and, like thousands of others seriously hurt in the civil war, he will likely need care well after the fighting is over. That's something doctors say a post-conflict Syria won't be able to provide.

Making things worse, there has been a sharp spike in serious injuries since the summer, when the regime began bombing rebel-held areas from the air, and doctors say a majority of the wounded they now treat are civilians.

This week, Fahed was recovering from brain surgery in an intensive care unit, his head bandaged and his body under a heavy blanket, watched over by Mariam, his distraught 22-year-old mother.

She said that after her first-born is discharged from the hospital in Atmeh, a village in an area of relative safety near the Turkish border, they will have to return to their village in a war zone in central Syria.

"We have nowhere else to go," she said.

Even for those who have escaped direct injury, the civil war is posing a mounting health threat. Half the country's 88 public hospitals and nearly 200 clinics have been damaged or destroyed, the World Health Organization says, leaving many without access to health care. Diabetics can't find insulin, kidney patients can't reach dialysis centers. Towns are running out of water-purifying materials. Many of the hundreds of thousands displaced by the fighting are exposed to the cold in tents or unheated public buildings.

"You are talking about a public health crisis on a grand scale," said Dr. Abdalmajid Katranji, a hand and wrist surgeon from Lansing, Mich., who regularly volunteers in Syria.

No one knows just how many people have been injured since the uprising against Assad's government erupted in March 2011, starting out with peaceful protests that turned into an armed insurgency in response to a violent crackdown.

More than 43,000 have been killed in the past 21 months, said Rami Abdul-Rahman, head of the Britain-based Syrian Observatory for Human Rights, basing his count on names and details provided by activists in Syria. He said the number of wounded is so large he can only give a rough estimate, of more than 150,000.

Casualties began to rise dramatically at the start of the summer. At the time, the regime, its ground troops stretched thin, began bombing from the air to prevent opposition fighters from gaining more territory.

Seemingly random bombings have razed entire villages and neighborhoods, driving terrified civilians from their homes, with an estimated 3 million Syrians of the country's 23 million population now displaced.

Moreover, the regime has begun dropping incendiary bombs that can cause severe burns, according to amateur video and witness accounts.