Which of the following diseases is/are caused by viruses?
Smallpox
Common cold
AIDS
A virus is a small infectious agent that replicates only inside the living cells of other organisms. Viruses can infect all types of life forms, from animals and plants to microorganisms. Example: Smallpox is caused by the Variola virus. Common cold is caused by Rhinovirus. AIDS is caused by Human Immunodeficiency Virus (HIV).