Stephane Dujarric told reporters today that "it's very important not to isolate these countries" as it would worsen their political and economic situations. He says aid groups need access to the region.
The first reported US case involves a man who flew from Liberia to visit relatives. His travel took him through Brussels and Washington before reaching Texas.
Dujarric emphasized the importance of screening at travelers' departure and arrival.
The UN has lost one staffer in Liberia to "probable" Ebola.