At least one child has died since the outbreak began in November, with others vulnerable due to a lack of vaccinations.
An outbreak of measles is threatening the lives of children in Guinea, one of West Africa's poorest countries.
The UN children's agency UNICEF says one child has been confimed dead since the outbreak began in November, but the real number may be much higher.
A UN survey shows only 37 percent of children in Guinea get all the vaccines they need to stay healthy, making the majority vulnerable. Thirty-seven cases of measles have been confirmed in the capital Conakry.