The WHO says the world is at risk from a deadly disease. They do not know what it looks like. They called it 'Disease X'. It could come from an unknown micro-organism. Disease X could spread around the world before we know about it. The WHO is putting a lot of money into research. It is preparing a plan for an outbreak. It said: "Disease X represents the knowledge that a serious international epidemic could be caused by [an unknown virus].

Disease X could come from many places. An existing disease could get stronger; terrorists could make bio-weapons; DNA-changing technology could make totally new viruses. The U.S. Centers for Disease Control and Prevention said: "Scientists estimate that…6 out of every 10 known infectious diseases in people are spread from animals." Today, people live closer together and travel the world more. This will make it easier for diseases to spread.