The rainy season in West Africa is compounding difficulties in getting supplies delivered and new treatment centers built as donors rush to isolate people infected with the deadly Ebola virus and stop its rapid spread, U.S. officials said.

Nancy Powell, newly appointed as the U.S. State Department's envoy to coordinate its Ebola response, said the priority is to isolate as many people as quickly as possible. But that faces significant logistical hurdles.

"Infrastructure challenges in the rainy season is one of the biggest difficulties. And you add the rain and getting materials out of the capital and it is very difficult," Powell said in a news briefing last week.