Shannon is correct. I think of it as a microscopic spider. Imagine you touch something at Walmart and get your hands infected you wipe your nose with your hands. The virus enters the nose or wherever you let it go to. It crawls into one cells(now host cell) it injects genetic material of the virus into the host cell, the host cells the explodes and the micro-microscopic particles spread onto more and more cells and break those. While your immune system tries to defend you against them, sometime your immune system wins and you don’t get sick but sometime is looses and that is how we get sick.
