Viruses are the of the microbes and are generally harmful to .
They come in many different shapes and have no .
Viruses cannot by themselves.
They require a cell in which to live and reproduce.
Once inside the host cell, they rapidly destroying the cell in the process.
Viruses can get into our cells in different ways including landing on our cells and injecting their into them.
Others break down the cell then get inside.
Once inside our cells they hijack them and make millions of of themselves.
Each of these can then go off and other cells.