Washington, Sep 3 (IANS/EFE) The head of US Centers for Disease Control and Prevention (CDC) Tuesday warned of the risk that the Ebola outbreak could get out of control without a greater worldwide response.

"This is not just a problem for Africa. This is a problem for the world, and the world needs to respond," Efe quoted CDC director Tom Frieden as saying, after his return from a tour through the affected zone. CDC is an agency of the US department of health and human services.

Despite the efforts of the United States and other countries, the number of deaths from Ebola virus is increasing at an accelerating rate and authorities fear that fatalities will mount even more before the situation can be brought under control, Frieden said.

The World Health Organisation warned last week that the number of people infected with the virus could exceed 20,000.

"We know how to stop Ebola," Frieden said. "The challenge is to scale it (the response) up to the massive levels needed to stop this outbreak."

Ebola has already killed at least 1,550 people in Liberia, Guinea, Sierra Leone and Nigeria.

"We have seen outbreaks of Ebola before. This is the first epidemic spreading widely through many countries, and it is spiralling out of control," the CDC chief said.

"It is bad now, much worse than the numbers show. It is going to get even worse in the very near future," he added.