Résumé:
Viruses are now part of our daily life, and the best example of this is the spread of the SARS-CoV-2 virus (responsible for the Covid-19 pandemic), this year to the point where life has stopped, this which inspired us to do this work. This document is divided into two chapters; in the first chapter we give a definition of viruses then their characteristics which concern their genome (DNA or RNA and its polarity), their enveloped or naked structure, their classification (according to Baltimore and according to the ICTV). In the second chapter we describe the stages of their multiplication cycle, the replication of their genome and the expression of their genes. Then we enriched this with examples of the multiplication cycle (example of influenza virus, HIV-1, SARS-COV-2). The document was finalized with a brief review of the consequences of viral multiplication for the infected cell and genetic variability of viruses. All the chapters described have been enriched by examples of more or less known viruses.
