A doctor who recently returned to New York from treating ebola patients in Guinea has tested positive for the disease.
It's the fourth case in the US but the first in New York City.
And Mali has confirmed its first case of ebola, in a two year old girl, making it the sixth country in West Africa to be affected by the crisis.
In New York, 33-year-old Craig Spencer has been placed in isolation, about a week after he got back from West Africa.
New York City's mayor, Bill De Blasio, says residents have no reason to be concerned:
