More than 11 million people have been forced from their homes amongst clashes between supporters of President Bashar al-Assad and those opposed to his rule - as well as jihadist militants from the so-called Islamic State.
The United Nations has estimated that over 13 million Syrians are in need of immediate humanitarian assistance. An estimated 6.5 million people are internally displaced in Syria, with over 5 million Syrians seeking asylum internationally.
Closed borders, appalling living conditions and limited assistance have compounded their suffering. People fleeing violence live in camps, improvised shelters or with host families.
Violence, attacks on health facilities, the absence of government authorisation and the reneging by armed groups on guarantees of safety for MSF teams have been major obstacles to a more extensive program of medical humanitarian aid in Syria.