The World Health Organization is "gravely concerned" about the "potential international spread" of Ebola beyond the outbreak in West Africa, the agency's regional office said Thursday.
"This is no longer a country specific outbreak but a sub-regional crisis," it added.
With nearly 400 deaths and more than 600 cases so far, the Ebola outbreak is the deadliest and largest since the virus was first detected in 1976.
The outbreak started in Guinea back in February. But it quickly jumped borders into neighboring Liberia and Sierra Leone.
Several international health agencies, including Doctors Without Borders, and the U.S. Centers for Disease Control and Prevention have rushed to help halt the spread of the disease.
But those efforts haven't been enough, WHO said. The virus continues to pop up in new cities and towns. Most recently cases appeared in Liberia's capital city, Monrovia, where about 1 million people live.
"As the number of deaths and cases of Ebola virus continues to rise in Guinea, Liberia and Sierra Leone, the World Health Organization is warning that drastic action is needed," the agency said.
Seventy cases have been reported in Guinea's capital, Conakry, which has an international airport. But the risk of Ebola spread to the U.S. or Europe is very low, infectious disease specialists told Shots Wednesday. Most of the travel in the region is local.
There is no cure or vaccine for Ebola. In this particular outbreak, the virus has killed about 50 to 60 percent of the people known to be infected.