Illustration of the envelope glycoprotein from the Zaire ebolavirus. This protein is involved in attachment to host cells and membrane fusion. Zaire ebolavirus is one of four that causes ebola virus disease (EVD) in humans and nonhuman primates. EVD is a severe and often fatal disease with symptoms including fever, fatigue, muscle aches, vomiting, diarrhoea and haemorrhaging (internal bleeding). Zaire ebolavirus is the only strain that there is an effective vaccine against.