A virus is a small organism which can infect other biological organisms.
Viruses can only reproduce by invading and taking over cells as they lack the
cellular machinery for self reproduction.
They cause diseases in human beings, animals, plants and bacteria.
Examples of human diseases caused by viruses include the common cold,
AIDS, and cold sores.
Viruses are not affected by antibiotics,
the drugs used to kill bacteria.
HIV/AIDS - Micro-organism