The Ebola epidemic centred on Guinea was, by early June last year, the deadliest ever recorded. Foreign workers were being evacuated and leading disease fighters warned the virus could soon spread across West Africa. But the World Health Organisation resisted sounding the alarm until August, partly for political reasons, despite the fact that senior staff in Africa proposed doing so in June, emails have revealed. The two-month delay, some argue, may have cost lives. More than 10,000 are believed to have been killed by the virus since WHO first announced the outbreak a year ago. The WHO has acknowledged acting too slowly to control the epidemic. In its defence, the agency says the virus's spread was unprecedented and blames several factors, including lack of resources and local intelligence. Internal documents, however, show WHO's top leaders were informed of how dire the situation was. But they held off on declaring an emergency in part because it could have angered the countries involved, interfered with their mining interests or restricted the Muslim pilgrimage to Mecca in October. Declaring an emergency was "a last resort," Dr Sylvie Briand, who runs WHO's pandemic and epidemic diseases department, said in a June 5 email to a colleague who floated the idea. "It may be more efficient to use other diplomatic means for now." Five days after Briand's email, WHO Director General Dr Margaret Chan Fung Fu-chun - who previously served as Director of Health in Hong Kong - was sent a memo that warned cases might soon appear in Mali, Ivory Coast and Guinea Bissau. But it went on to say declaring an international emergency or even convening a committee to discuss it "could be seen as a hostile act". "That's like saying you don't want to call the fire department because you're afraid the trucks will create a disturbance," said Michael Osterholm, an expert at the University of Minnesota. The signs this was no ordinary outbreak - the panic, the health workers' deaths, and the urban spread of the virus - were there from the beginning. Many are recorded in a memo sent to WHO's Africa director on March 25. In mid-April, an experienced Ebola expert with WHO's Africa office wrote to Geneva, with disturbing news that many staff at a leading hospital in Guinea had been exposed to the virus. "What we see is the tip of an iceberg," Jean-Bosco Ndihokubwayo wrote in an email, writing in capitals: "WE NEED SUPPORT." The Ebola outbreak erupted at a difficult time. The WHO was also struggling to contain polio outbreaks - which it had declared an international emergency in May - and Mers (Middle East respiratory syndrome). At a June 2 meeting, one scientist said the agency was "overwhelmed". Declaring an international emergency might not necessarily have fixed all those problems but would have acted as a global distress signal. Dr Joanne Liu, the international president of Doctors Without Borders, said she had been lobbying Chan to sound the alarm. "You have the legitimacy and the authority to label it an emergency," Liu said she told Chan in a July 30 meeting in Geneva. "You need to step up to the plate." The emergency was eventually declared on August 8, by which point nearly 1,000 people had already died from Ebola.