Cells are very small capsules that make up humans, altough plants, fungi, bacteria, and more are also made of cells. Some living things have just a single cell.The virus will latch onto a cell, and penetrate the walls of the cell with it's "needles" (the sharp bits). The virus will then continue to inject its DNA into the cell. This will cause the cell to create clones of the virus. After filling up with viruses, will 'pop' and release many duplicates of the starting virus, back into the blood. The virus is much smaller than a cell, and cannot walk with its "legs", which are just used for stability once it has latched onto a cell.
This video explains how pathogens work, and how our immune system protects against them.
