Viral contamination, replication, healing thanks to the immune system. The story begins with a sick child who coughs and infects the boy in front of her. The virus in the boy's body uses lymphocytes to replicate. It enters the cell, deposits its viral RNA there which transforms into viral DNA. The latter attaches to the DNA of the lymphocyte which will reproduce the different parts of the virus including its viral DNA, replicating the virus in large numbers. The boy begins to cough too. Then the viruses replicate more and more, The boy has a fever and sweats. His immune system is activated. Macrophages (green cells) will phagocyte virus and infected cells, and trigger the production of antibodies (blue Y) by other lymphocytes (blue cells) which will attach to viruses in order to destroy them. After a few days, the invasion is under control and the boy can resume his normal life.