Viruses are supposed to be the biological weapons of the future. They are everywhere. Millions of viruses around us, interact, invade. Virus able to evolve, change your environment, jump from one species to another. Scientists continue its track. Looking hiding in nature, in animals that viruses use to travel from one place to another planet ... but not always find them. In recent decades there have been many diseases that so far only affected animals. These diseases, caused by very aggressive virus, appear with high frequency in Africa, and requires a high financial contribution in order to eradicate them. Marburg virus, influenza, dengue, yellow fever, Ebola virus, human immunodeficiency virus, Epstein-Barr... To find answers we enter for the first time in the High Security Center Biological where the most dangerous viruses in history and the emerging service. And the World Health Organization explains how he manages to monitor the emergence of new viruses and diseases in any country.