The UN World Health Organization has declared the Ebola epidemic an “international health emergency”.
Guinea, Liberia and Sierra Leone are battling the Ebola virus, with at least 932 people killed in those countries.
Cases are also showing up in Nigeria.
The WHO declaration comes after two days of emergency meetings.
The United Nations health agency described this as the worst outbreak in 40 years of tracking the disease.
Officials said “a coordinated international response” is needed to contain Ebola.
The United States is sending experts to Liberia, including 12 specialists from the Centres for Disease Control and Prevention, and a 13-member disaster assistance response team from the US Agency for International Development.
Two Americans who were in Liberia are undergoing treatment at Emory University Hospital in Atlanta.