Viruses and cells have "lock and Key" forms, Viruses trick the cell into letting them in by snugly fitting into the "lock" of the cell, once inside it tells the cell to multiple the virus, which creates a chain reaction of spreading the virus through the body. I think this is only a Lytic cycle, theirs two types of viruses and how they spread.
An infected person sneezes, coughs, etc. near you. You inhale the virus particle, and it attaches to cells lining the sinuses in your nose. The virus attacks the cells lining the sinuses and rapidly reproduces new viruses. The host cells break, and new viruses spread into your bloodstream and also into your lungs.
