The Ebola outbreak in Nigeria is almost over after an ordeal that began in July when a sick man with US-Liberian citizenship flew there from Liberia US health authorities said today. The virus's incubation period is 21 days and after two of these periods have passed without any new cases officials can declare an outbreak over. Therefore since there have been no new cases since August 31 the West African nation should be able to announce a formal end to its outbreak on October 12 a spokesman for the US Centers for Disease Control and Prevention told AFP. Meanwhile the