Why do we still have so much uncertainty about the Ebola virus?

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Now Playing, Trump says we should ‘stop using Ebola’ Now Playing – Trump’s top advisers on the Ebola outbreak Now Playing Trump backs off on calling for immediate U.S. troop withdrawal from Africa Now Playing The new Ebola outbreak at a glance Now Playing ‘The world is looking at us’: Trump says he’s ‘totally fine’ with US troop withdrawal Now Playing US President Donald Trump talks to reporters in the White House briefing room ahead of a press conference with Japanese Prime Minister Shinzo Abe: ‘I have never met an issue more important to me than this’ Now Play Trump calls for US troop withdrawing from Africa: ‘We need to be in a stronger position’ Now Watch: Trump says the U.K. will ‘never’ be ‘part of’ European Union Now Playing What to know about Ebola: CDC Now Playing Here are the latest developments from around the world, including the U,S., UK, Australia, New Zealand and South Africa.

Now Playing WATCH: What you need to know if you’re a parent with Ebola Now Playing UK Prime Minister Theresa May calls for a pause in Ebola cases in England: ‘This is the right thing to do’ Now What to Know: What Ebola vaccine will the U