During her monthlong stay in Syria in mid-April, Dr. Nobuko Kurosaki, who leads the Japanese arm of Doctors Without Borders, heard gunshots and explosions all around her.

Although it wasn't the first country racked by civil war she had visited, the fighting there was more chaotic and intense than the others, she said. But this is the life she has chosen: Kurosaki said she goes to countries suffering from conflict, epidemics and natural disasters because "doctors are needed."

The Syrians injured in the conflict had to decide whether to risk the constant bombing to see a doctor or stay at home with unabated pain, said Kurosaki, 56.