The director of the Centers for Disease Control and Prevention warned that the “window is closing” to stop the Ebola outbreak in West Africa before it goes global. At a press conference Tuesday, Tom Frieden stressed the need to step up efforts to combat the virus, which he described as “spiraling out of control” in Africa. He outlined how hard it is to care for Ebola victims and for the burial teams to “keep up” with the death toll. He also warned that Americans weren’t immune from the epidemic. Still, he did offer a few notes of optimism. “We can turn this around,” said Frieden. “We can chip away at the challenges.” It was announced Tuesday that another American doctor stationed in Monrovia, the capital of Liberia, tested positive for the virus. The obstetrician isolated himself and has been transferred to a special Ebola unit. More than 1,300 have died from Ebola so far.