An outbreak of Ebola virus disease (EVD), caused by Zaire ebolavirus, beginning in south-eastern Guinea in December 2013,1 but not formally identified until 23 March 2014, has spread to the neighbouring countries of Liberia, Sierra Leone and Mali, with limited transmission to Nigeria, USA, Spain and Senegal. The cumulative total of cases and deaths is 14 413 and 5177, respectively as of 11 November 2014, making this outbreak around 45 times larger than any previous one. No validated treatment is yet available, although numerous experimental therapies are being employed following the decision of the WHO Panel on Unregistered Interventions.