It started as a deadly but little-known outbreak in West Africa, but the lethal and unchecked spread of the Ebola virus dominated U.S. headlines for much of 2014, making it one of the year's top health news stories.

According to the latest World Health Organization figures, nearly 20,000 reported cases of Ebola -- including more than 7,700 deaths -- have occurred since the outbreak began earlier this year in Guinea, Liberia and Sierra Leone. By September, the first of 11 cases treated in the United States began to worry Americans, and two cases acquired in the United States -- nurses treating an Ebola-infected patient at a Dallas hospital -- sparked fears the disease might spread in this country.

Under criticism for what some considered an uneven response to the threat, the U.S. Centers for Disease Control and Prevention in December designated 35 specially equipped hospitals across the United States as Ebola treatment centers.

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