The virus invades the host cell, takes it over, causing it to make copies of the viral DNA or RNA which destroys the host cell, releasing new viruses. In this way viruses are unique because they are only alive and able to multiply inside the cells of other living things.
The virus particle attaches itself to the host cell before penetrating it. This then allows the virus to use the host cell’s ingredients to copy its own genetic material before leaving the host cell once the process is complete.
This process slowly uses up the host cell’s membrane leading its to cell death. Once the virus leaves the host cell it is ready to enter a new cell and multiply.