According to the World Health Organization, there are more than 3,000 cases.
More than 1,500 people have died from the virus in West Africa.
But many suspect the numbers are much higher, including the director of the Centers for Disease Control and Prevention (CDC).
"We've seen outbreaks of Ebola before. This is the first epidemic spreading widely throughout country and many countries, and it's spiraling out of control," Director for Centers for Disease Control and Prevention Dr. Tom Frieden said. "It's bad now, much worse than the numbers show. It's going to get even worse in the very near future and our window of opportunity to turn it around is closing, but it's not yet closed. The crucial thing we need to do is to act fast. Action today is worth much more than action within a couple of weeks or a month or two."
The Ebola vaccine trial will take place on the campus of the National Institutes of Health (NIH) in Maryland.
It will first be given to healthy human volunteers to see if they suffer any harmful side effects. If deemed safe, it will then be given to another small group of volunteers.
NIH expects to reveal the results of the trial by the end of the year.
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