ABIDJAN (Reuters) - A total of 4,493 people have died from the world's worst Ebola outbreak on record as of Oct. 12, statistics released by the World Health Organization showed on Wednesday.

WHO said a total of 8,997 confirmed, probable and suspected cases of Ebola had been reported in seven countries, with the vast majority of these in the West African nations of Liberia, Sierra Leone and Guinea.

In Spain and the United States, a handful of healthcare workers are ill, while Senegal and Nigeria appear to have prevented further spread of the disease, the WHO said.

"It is clear...that the situation in Guinea, Liberia, and Sierra Leone is deteriorating, with widespread and persistent transmission of (Ebola)," the WHO report stated.

It said an increase in the number of new cases in Guinea - where 843 people are now believed to have died from the disease - was driven by a spike in infection in the coastal capital Conakry and the nearby district of Coyah.

In Liberia, the U.N. health agency said that problems with data gathering made it hard to draw conclusions about the evolution of the epidemic, with the number of cases in the capital Monrovia almost certainly significantly under-reported.

Liberia accounts for more than half the number of dead - 2,458 - and for 4,249 confirmed, probable and suspected cases.

Nonetheless, in Liberia's northern Lofa county -- the former epicenter of the outbreak on the border with Guinea -- there appeared to be a genuine fall in the number of cases, it said.

In Sierra Leone, transmission of the disease was rampant with 425 new cases between Oct. 6 and 12, WHO said, with the capital Freetown and the neighboring western districts of Bombali and Port Loko the hardest hit.

(Reporting by Joe Bavier and Daniel Flynn; Editing by David Lewis and Sonya Hepinstall)