Viruses are very small infectious agents. They’re made up of a piece of genetic material, such as DNA or RNA, that’s enclosed in a coat of protein.
Viruses invade cells in your body and use components of those cells to help them multiply. This process often damages or destroys infected cells.
A viral disease is any illness or health condition caused by a virus.
There are many viral diseases. Some, such as the common cold or the stomach flu, are minor and go away on their own within a few days. Others, however, are more serious.