(Adds WHO spokesperson)
DAKAR, June 18 (Reuters) - The death toll from an outbreak of Ebola in Guinea, Liberia and Sierra Leone has hit 337 since February, the U.N. World Health Organization said on Wednesday, as weak local health services struggle to contain the highly contagious disease.
WHO said 47 new cases and 14 deaths had been reported in the region in the last week alone, months after international experts were first sent to help tackle the widest-spread outbreak of Ebola recorded in Africa.
Guinea remains worst affected, with 264 Ebola-related deaths, the WHO data showed, but the toll in Sierra Leone and Liberia has recently spiked, hitting 49 and 24 respectively.
WHO has tried to coordinate the regional response but imposing the restrictions needed to control such an infectious disease has proven difficult. WHO said last month an earlier dip in cases masked the seriousness of the outbreak.
WHO's spokeswoman Fadela Chaib said more work needed to be done in tracing possible victims and ensuring more people report to health facilities to increase their chances of recovery and avoid infecting others.
The outbreak has been made more complicated because it involves multiple locations in 3 countries, and frequent cross-border movements by people, she said.
"This makes this one of the most challenging Ebola outbreaks ever," she said by email.
Guinea's new cases were reported in Gueckedou, a remote southeast region where the outbreak was first confirmed, but also in Boffa, hundreds of kilometers (miles) to the northwest of the capital city Conakry.
Liberia reported four deaths in its capital Monrovia on Tuesday, the first to be confirmed in the sprawling ramshackle seaside city.
Sierra Leone's toll has risen rapidly since it confirmed its first deaths in late May.
The outbreak has led to some restrictions on flights and trade in the region but international mining firms operating in the three countries say operations have not yet been affected.
Discovered in 1976 after an outbreak in the Democratic Republic of Congo, Ebola has a fatality rate of up to 90 percent and there is no vaccine and no known cure.
The virus initially causes raging fever, headaches, muscle pain, conjunctivitis and weakness, before moving into more severe phases of causing vomiting, diarrhea and hemorrhages. (Reporting by David Lewis, Bate Felix and Daniel Flynn; Editing by James Macharia)