Last checked at 
(Corrects to show dead doctor did not treat Sawyer)
* Number of cases possibly 2-4 times higher than reported
* 12,000 local staff, 750 international experts needed
* Operation to combat outbreak to cost $490 mln
* Nigeria reports possible spread to main African oil hub
By Stephanie Nebehay and Tim Cocks
GENEVA/LAGOS Aug 28 (Reuters) - The Ebola epidemic in WestAfrica could infect more than 20,000 people, the U.N. healthagency said on Thursday, warning that an international effortcosting almost half a billion dollars is needed to overcome theoutbreak.
As the World Health Organisation (WHO) announced itsstrategic plan for combatting the virus, GlaxoSmithKline said an experimental Ebola vaccine is being fast-tracked intohuman studies and it plans to produce up to 10,000 doses foremergency deployment if the results are good.
The WHO estimates it will take six to nine months to haltthe Ebola epidemic in West Africa, while Nigeria said onThursday that a doctor indirectly linked to theLiberian-American who brought the disease to the country haddied in Port Harcourt, Africa's largest energy hub.
So far 3,069 cases have been reported in the outbreak butthe WHO said the actual number in Guinea, Sierra Leone, Liberiaand Nigeria could already be two to four times higher.
"This is not a West Africa issue. This is a global healthsecurity issue," Bruce Aylward, the WHO's AssistantDirector-General for Polio, Emergencies and CountryCollaboration, told reporters in Geneva.
With a fatality rate of 52 percent, the death toll stood at1,552 as of Aug. 26. That is nearly as high as the total fromall recorded outbreaks since Ebola was discovered in what is nowDemocratic Republic of Congo in 1976.
The figures do not include deaths from a separate Ebolaoutbreak announced at the weekend in Congo, which has beenidentified as a different strain of the virus.
Aylward said tackling the epidemic would cost an estimated$490 million, involving thousands of local staff and 750international experts. "It is a big operation. We are talking(about) well over 12,000 people operating over multiplegeographies and high-risk circumstances. It is an expensiveoperation," he said.
The operation marks a major ramping up of the response bythe WHO, which had been accused by some aid agencies of reactingtoo slowly to the outbreak.
A wider United Nations -led plan being launched by the endof September is expected to provide support for the secondaryeffects of the outbreak on food security, water, sanitation,primary and secondary healthcare and education, the WHO said.
EXPERIMENTAL DRUGS
Early this month, the WHO called the current Ebola outbreakan "international health emergency". Concerns that the diseasecould spread beyond West Africa have led to the use of drugsstill under development for the treatment of a handful of cases.
Two American health workers, who contracted Ebola whiletreating patients in Liberia, received an experimental therapycalled ZMapp, a cocktail of antibodies made by tiny Californiabiotech Mapp Biopharmaceutical. They recovered and were releasedfrom hospital last week.
The virus has already killed an unprecedented number ofhealth workers and is still being spread in a many places, theagency said. About 40 percent of the cases have occurred withinthe past 21 days, WHO statistics showed.
Previous Ebola outbreaks have mainly occurred in isolatedareas of Central Africa. However the current epidemic has spreadto three West African capitals and Lagos, Africa's biggest city.The WHO said special attention would need to be given tostopping transmission in capital cities and major ports.
Authorities in Nigeria announced the doctor's death in PortHarcourt, the oil industry hub of Africa's largest crudeexporter. The doctor had treated a patient who had been incontact with Patrick Sawyer - a U.S. citizen who died in Lagosafter flying in from Liberia last month - but who had evadedquarantine in Lagos.
Health Ministry spokesman Dan Nwomeh wrote in his Twitterfeed that 70 people who had been in contact with Sawyer were nowunder observation in the town
According to new figures released on Thursday, Nigeria hasrecorded 17 cases, including six deaths, from Ebola, sinceSawyer collapsed upon arrival at Lagos airport in late July.
AID EFFORT CHOKED OFF
The Lagos case contributed to the decision by a number ofairlines to halt services to Ebola-affected countries. AirFrance said on Wednesday it had suspended flights toSierra Leone on the advice of the Frenchgovernment.
The WHO has advised against travel bans and border closures,which some countries in the region have also implemented, saying they risked creating food and supply shortages.
"We assume current airline limitations will stop within thenext couple of weeks. This is absolutely vital," Aylward said."Right now the aid effort risks being choked off."
West African health ministers meeting in Ghana on Thursdayechoed the WHO's concerns and called for the reopening ofborders and an end to flight bans. (Additional reporting by Kwasi Kpodo in Accra, Ben Hirschler inLondon and Sharon Begley in New York; Writing by Joe Bavier;Editing by Daniel Flynn and David Stamp)
