The number of people worldwide infected with the Ebola virus is closing in on 10,000, according to world health officials.The Centers for Disease Control reports 9,916 people are infected worldwide, with 5,481 having died from Ebola infection.Earlier this week, WHO declared Nigeria free of the Ebola virus. It was required to be free of the disease for 42 days.While WHO was first alerted to the Ebola outbreak in March 2014, officials say investigations show it started in December 2013.In the U.S., two nurses are the only known cases of Ebola.