virus first emerged in the Guéckédou region of Guinea, at a crossroads with both Liberia and Sierra Leone See the Ebola outbreak mapped 31 March On 31 March the WHO confirmed the outbreak was now international, spreading first into Liberia's northern-most Lofa region See the Ebola outbreak mapped 27 May The virus spread to Sierra Leone at the end of May - just as agencies were hoping the worst was over See the Ebola outbreak mapped 27 July In Sierra Leone the virus boomed, and then it spread to Nigeria when the Liberian diplomat Patrick Sawyer flew from Monrovia to Lagos See the Ebola outbreak mapped 9 August The Nigeria cases sparked fears around the world, and there have now been deaths in Spain and Saudi Arabia involvingpeople who had travelled to West Africa. The numbers of cases continue to rise See the Ebola outbreak mapped 17-20 September In mid-September, Senegal confirmed its first case linked to the Ebola outbreak, a development the WHO described as a top priority emergency. Numbers of cases continued to grow exponentially in Guinea, Sierra Leone and Liberia, as experts warned they could number one million by January if not contained See the Ebola outbreak mapped 8 October Two cases of Ebola have now been reported in the US and Europe - the first times the virus has been contracted among health workers outside Africa

Mr Duncan's diagnosis has heightened fears that the deadly virus could spread from West Africa, where the epidemic started in March and has since killed more