* Liberian president apologises to health workers
* Sierra Leone doctor confirmed with Ebola
* Saudi Arabia says Ebola suspect tests negative
* Zambia, Gambia impose new restrictions (Adds Saudi Ebola test, Liberia measures, quote)
By Saliou Samb
CONAKRY, Aug 9 (Reuters) - Guinea closed its borders with Sierra Leone and Liberia on Saturday in a bid to halt the spread of an Ebola epidemic that has killed nearly 1,000 people in the three countries this year.
Authorities said the decision was taken primarily to prevent infected people crossing into Guinea, where at least 367 people have died of Ebola since March and 18 others are being treated in isolation.
The West African Ebola outbreak is the worst in history and the World Health Organization (WHO) said on Friday it represents an international health emergency that will likely continue spreading for months.
It has put a severe strain on the health systems of affected states and governments have responded with a range of measures including national emergencies declared in Sierra Leone, Liberia and Nigeria, which confirmed seven cases of Ebola in Lagos.
"We have provisionally closed the frontier between Guinea and Sierra Leone because of all the news that we have received from there recently," Health Minister Rémy Lamah said, noting Guinea had also closed its border with Liberia.
The measures had been taken in consultation with the two neighbours, Guinea's Minister for International Cooperation, Moustapha Koutoub Sano, told a news conference. There was no immediate comment from Liberia and Sierra Leone.
While Guinea's official land border crossings with the countries will shut, it will be extremely difficult to prevent people in rural areas crossing its long and porous frontiers.
Ebola is one of the deadliest diseases known to humanity. It has no proven cure and there is no vaccine to prevent infection. The most effective treatment involves alleviating symptoms that include fever, vomiting and diarrhoea.
The rigorous use of quarantine is needed to prevent its spread as well as high standards of hygiene for anyone who might come into contact with the disease.
These measures have proved hard to enforce given that Ebola has spread in rural parts of some of the world's poorest countries. The task is made harder because of mistrust of health workers in areas with inadequate public health services.
The WHO said on Friday 961 people have died during the outbreak and 1,779 have been infected.
TOLL ON HEALTH WORKERS
Ebola has reaped a high toll on health workers who have acted as first responders. Liberia's President Ellen Johnson Sirleaf apologised to health workers on Saturday.
"If we haven't done enough so far, I have come to apologise to you," she told hundreds of health workers who gathered at Monrovia's City Hall for a meeting with her government.
Johnson Sirleaf pledged up to $18 million to health workers to help with insurance and death benefits, to fund more ambulances and to increase the number of treatment centres.
Sierra Leone's Health Ministry said a senior physician had contracted the disease at the Connaught referral hospital in the capital Freetown. Dr Modupeh Cole contracted the disease "after treating a patient ... who was later proved to have the virus and died," said ministry spokesman Sidi Yahya Tunis.
Cole was taken to an Ebola treatment centre in eastern Kailahun district run by medical charity Medecins Sans Frontieres, Tunis said.
He is the latest Sierra Leonean medical practitioner to contract the virus. Its leading Ebola doctor, Shek Umar Khan, died of the disease last month and several nurses have died.
FRESH EBOLA TESTS
Authorities in Ghana said they were testing samples from a man from Burkina Faso who died while being transported to hospital in the Upper East region.
"He had fever and was bleeding from the nose so we are testing him for Ebola because we don't want to take chances," Yaw Manu, medical head at Bawku Presbyterian Hospital, said by telephone. Ghana has previously conducted around 20 Ebola tests, though none has proved positive.
Authorities in Benin also said on Saturday they were testing a patient for Ebola, the second suspected case in the country, while Saudi Arabia's Health Ministry said initial tests on a dead Saudi citizen suspected of having Ebola were negative.
International alarm over the spread of the disease increased last month when a U.S. citizen died in Nigeria after travelling there by plane from Liberia. Since then, other countries with no cases of the disease have taken measures as a precaution.
Zambia said it would restrict the entry of travellers from countries affected by the virus and would ban Zambians from travelling to those countries, in one of the strictest moves by any nation outside of West Africa.
Zambia's Health Ministry also advised against holding any "international events" such as conferences and other gatherings, citing concerns about controlling potential outbreaks.
Gambia's Ministry of Transport said any planes flying to the capital Banjul should not pick up passengers at airports in Conakry, Freetown or Monrovia. (Additional reporting by Umaru Fofana in Freetown, Kwasi Kpodo in Accra, David Dolan in Johannesburg, Samuel Elijah in Cotonou, Pap Saine in Banjul, Clair MacDougall in Monrovia and Amena Bakr in Doha; Writing by Matthew Mpoke Bigg; Editing by Janet Lawrence)