Virus (thing)

    head            tail
 ____|____  _________|_________
'         ''               __  '
  ______                __/  __
 /      \              /  __/
/ (((((  \_|---------_|\_/
\  ))))) /"|---------"|/ \__
 \______/              \__  \__
          /   /      /    \__
  / collar   /      /            \
 /          /       \            tail fibers
/         sheath    base plate
\
 protein coat
 
 (((
  ))) nucleic acids (inside protein coat)

Typical cycle for the spread of viral infection:

1. The virus attaches by it's tail fibers to a cell wall by recognizing certian features on the cell's receptor sites.
2. The virus works like a syringe by breaking down the cell wall at the base plate, and then using the sheath to pump the DNA through the cell wall into the cell.
3. The empty virus capsule (protein coat, sheath, etc) is discarded.
4. The cell begins making hundreds of copies of the entire virus using the DNA it was injected with.
5. The cell walls break down and release these viruses into the host.