The lessons of virus. What is it? Where we meet him ? Structure of virus? Transmission? Prevention and treatment? For know better the virus ( a biologic entity) we became enter into the etymology of virus for the prevention and care the organism. The word’ significand comes of Latin” vïrus” ( poison) with the parasite characteristic multiplication his form into intern cellular in organism infecting all the form of life( animal, plant, people) founding inti all ecosystem of Terre( being the entity more complex in absolute). The science that studied the virus is named virology( a specialty of microbiology). Being a form of viral particle know as virion , they can found inactive at intern of cellule when they don’t in phase of infection. Them structure is three parts: genetic material build by DNA or RNA, protein coating( capside) that surrounds and protege the genetic material, lipids that surround the protein coating  that there are out side of cellule. The virus have got virions that there are too small for to be view with a electronic microscope ( dimension of circa 2 mm of bacteria media dimension ). The origin of virus don’t is conclude, they can to be result of evolution by plasmidi ,transposoni, retrotrasposonim or degradation by cellular DNA. The influential virus is defend between person at other person crossing the contact with eat and the drinks. The more common form caused of virus is the influence, varicella, labial herpes arriving to complexity of  form virus : AIDS; EBOLA; Influence, SARS;COVID-19. The important thing is to found the source of infection for identified the virus  and to remove the transmission of virus . For the prevention is necessary isolation, lockdown , hygiene, disinfection , vaccines and the viral medicine.