By Umaru Fofana and Daniel Flynn FREETOWN/DAKAR (Reuters) - When two American aid workers recovered from Ebola after being treated with an experimental drug, the grieving family of Sierra Leone's most famous doctor wondered why he had been denied the same treatment before he died from the deadly virus. Sheik Umar Khan was a hero in his small West African country for leading the fight against the worst ever outbreak of the highly contagious hemorrhagic fever, which has killed 1,427 people mostly in Sierra Leone, Liberia and Guinea. When Khan fell sick in late July, he was rushed to a treatment unit run by Medecins Sans Frontieres (MSF) where doctors debated whether to give him ZMapp, a drug tested on laboratory animals but never before used on humans. Staff agonised over the ethics of favouring one individual over hundreds of others and the risk of a popular backlash if the untried treatment was perceived as killing a national hero. In the end, they decided against using ZMapp. Khan died on July 29, plunging his country into mourning. A few days later, the California-manufactured pharmaceutical was administered to U.S. aid workers Kent Brantly and Nancy Writebol who contracted Ebola in Liberia and were flown home for treatment. It is not clear what role ZMapp played in their recovery but the two left hospital in Atlanta last week. Khan is among nearly 100 African healthcare workers to have paid the ultimate price for fighting Ebola, as the region's medical systems have been overwhelmed by an epidemic which many say could have been contained if the world had acted quicker. In their village of Mahera, in northern Sierra Leone, Khan's elderly parents and siblings asked why he did not get the treatment. Khan saved hundreds of lives during a decade battling Lassa fever - a disease similar to Ebola - at his clinic in Kenema and was Sierra Leone's only expert on haemorrhagic fever. "If it was good enough for Americans, it should have been good enough for my brother," said C-Ray, his elder brother, as he sat on the porch of the family home. "It's not logical that it wasn't used. He had nothing to lose if it hadn't worked." Doctors who knew Khan and who were involved in the difficult decision, however, said it was based on sound ethical reasoning. Ebola, which is passed on by direct contact with the bodily fluids of infected persons, strikes hardest at healthcare providers and carers who work closely with patients. Victims suffer vomiting, diarrhoea, internal and external bleeding in the final stages of the disease, leaving their bodies coated in the virus. To treat the sick, doctors require training and protective clothing, both of them scarce in Africa. The outbreak - the first in West Africa - was detected five months ago deep in the forests of southeastern Guinea. But it was not until Aug. 8 that the World Health Organization declared an international health emergency and promised more resources. By decimating healthcare staff in countries that had only a few hundred trained doctors before the outbreak, Ebola has now left millions vulnerable to the next crisis, experts say. "Dr. Khan knew the risks better than anybody ... but if you work for months in overcrowded facilities, 18 hours a day, anyone will make a mistake," said Robert Garry, professor of microbiology and immunology at Tulane University in New Orleans, who worked with Khan for a decade. "The whole international community needs to look back and say we dropped the ball. We should've reacted faster to this." TENSE ATMOSPHERE To many in his impoverished country, Khan was a saviour for his pioneering work with Lassa fever, a disease endemic to the jungles of eastern Sierra Leone that kills 5,000 people a year. When Ebola struck, he became a figurehead for that fight, too, hailed by President Ernest Bai Koroma as a "national hero". Doctors involved in treating Khan were aware that - given sporadic violence against healthcare workers by a frightened local population - a misstep could prove costly. "Now you can look back at that and say it was a mistake," said American doctor Daniel Bausch of Tulane University, who worked with Khan and advocated giving him ZMapp at the time. "But there was a very tense atmosphere on the ground," he said. "If he had died from the drug, or even if it was perceived that he had, it could have had dangerous ramifications." Doctors also had ethical concerns about giving Khan priority treatment that hundreds of other infected people could not receive, since only a few doses of ZMapp had been manufactured. The president of Medecins San Frontieres - which has spearheaded the response to Ebola at clinics in Sierra Leone, Guinea and Liberia - said its doctors could not sanction use of a drug on Khan whose effects were unknown. "We didn't know what the consequences would be. We didn't know how sick he was and we didn't know how efficient it would be," Joanne Liu told Reuters. Khan, who had initially appeared to be recovering, was never told that the drug was available. Two weeks after his death, the World Health Organization approved the use of experimental drugs to tackle Ebola, on Aug. 12. However, the manufacturer of ZMapp, California-based Mapp Biopharmaceutical, said supplies of the drug are exhausted after the last doses were used in treating three African healthcare workers in Liberia last week. Like the two Americans, they are also recovering. Supplies of trial vaccines to prevent people contracting the disease are also very limited. With only 1,590 deaths from Ebola in the four decades that have passed since the virus was first isolated, all of them in poor African countries, drug firms have had little incentive to pursue research into the disease. Drug companies including GlaxoSmithKline are now fast-tracking vaccine trials in humans, amid fears that Ebola could be spread beyond Africa by air travel, after a U.S. citizen died in Nigeria after flying from Liberia. "We need to get healthcare workers vaccines. They are in harm's way," said Robert Garry, the main investigator at Viral Hemorrhagic Fever Consortium, a partnership of research institutes. He said the outbreak would last at least six months. "We need a lot more people to bring this under control. We haven’t seen the worst of this yet." "WHO WILL FILL MY SHOES" Khan knew from the first his work at the Kenema clinic would be dangerous. When he took over as head doctor there in 2004, his predecessor had bled to death from Lassa fever in the same ward. But after 11 years of civil war, there were few others who could do the job. The last but one of 10 children from a humble background, Khan always wanted to be a physician like his childhood hero Dr. Kamara, who ran a clinic in Mahera. Determined to enter Freetown's medical school COMAHS, Khan persisted despite being initially rejected. When he graduated, his father was too ashamed to visit this preserve of his country's elite and listened to the ceremony on the radio. "When the name Dr. Sheik Umar Khan was called out by the dean of the faculty, my father broke down in tears of joy," Khan's sister Mariama recalled. An extrovert and joker, Khan threw himself into his work in Kenema, a diamond-trading hub home to 130,000 people. His wife divorced him, complaining he only had time for his patients. When Ebola struck, Khan converted the bungalows of the clinic into an Ebola treatment centre, erecting a makeshift tarpaulin ward outside with 50 beds in three rows. With no proven cure, doctors simply tried to keep patients hydrated and free from other diseases as Ebola attacked their immune system. Though he feared for his life, he refused to abandon the understaffed clinic, even as nurses there began to fall sick. "If I leave, then who will come and fill my shoes," he told a friend from medical school, James Russel. Outbreaks in Central Africa lasted six to eight weeks, so when infections ebbed early in the epidemic, many assumed the worst had passed. It turned out to be a lull as relatives hid victims rather than going to hospitals regarded as death traps and a massive second wave of infection caught governments and international aid donors off guard. One of Khan's biggest challenges was resistance from local people, terrified of the medics in their white bodysuits and masks. A crowd attacked the Kenema facility, enraged by a rumour of cannibalism there. Several patients fled, spreading infection even wider. "My biggest problem ... is getting people to accept the disease," a frustrated Khan told Reuters in June. The first person infected in Sierra Leone was a "sowei" - a tribal healer. She claimed to have the power to treat Ebola and had attracted sick people to visit her from Guinea. Traditions of washing the dead helped spread the disease. Several women from neighbouring towns were infected at the sowei's burial. Already thinly staffed, the clinic was sapped by resignations and a strike after three senior nurses died. Khan was compulsive in checking his protective gear before entering the ward, using a mirror he called his "policeman". "I'm afraid for my life because, I must say, I cherish my life," he said. Bausch, sent by the WHO to Kenema in July to help train staff, said Khan had appeared worn down. Bausch had hired Khan to work at the Kenema clinic in 2004 but was so alarmed by the understaffing there, he had wondered if it should be shut down. "It's one thing for a foreign doctor who comes in for three weeks. But if you're Dr. Khan, head of the ward, it never stops," Bausch said. "Anyone would get infected." Khan's death sent shockwaves through Sierra Leone's small medical community of less than 150 doctors for its 6 million people - one of the lowest ratios in the world. Sierra Leone has one doctor per 45,000 inhabitants, according to the WHO, compared to a doctor for every 410 people in the United States. Other senior medical staff in the country have since died and the staff at Kenema has been decimated. "Once this nightmare is over, who in these countries will want to work treating patients with hemorrhagic fever?" said Bausch. "If it was hard before to get healthcare workers to do it, it will be even harder now."