"All the elements are present for a potentially deadly outbreak of disease -- severely overcrowded camps, low immunity and extremely poor water and sanitation infrastructure," said Souleymane Diabate, Unicef's representative in the CAR.
"This is a deadly combination for children. Unless we act now, we could have a disaster on our hands."
With at least seven cases of measles confirmed, the UN agency is racing to halt the spread of the potentially deadly disease by vaccinating 210,000 children displaced by violence in the country.
At Bangui airport, where about 100,000 displaced people have set up camp, three cases of measles have been confirmed, said Unicef.
The landlocked country sank into chaos when rebels from the Seleka movement launched a coup in March, and installed Michel Djotodia as the country's first Muslim president.
Djotodia has since officially disbanded the rebels, but has proved unable to keep them in check.
Instead the rebels have gone on killing, raping and pillaging, prompting Christians to form vigilante groups in response and sparking a deadly cycle of revenge attacks.
More than 1,000 people have been killed in the past month alone and nearly a million have been displaced since the coup.
