infection by a virus that is pathogenic to humans

An infection caused by a virus. A virus cannot replicate without a host cell and is not typically considered to be a living organism - unlike bacteria, which can be free-living.

An infection involving a virus, the smallest disease causing organism. Viruses can be harmless (e.g. warts), or devastating (e.g. the aids virus).

Infection caused by the presence of a virus in the body. Depending on the virus and the person's state of health, various viruses can infect almost any type of body tissue, from the brain to the skin. Viral infections cannot be treated with antibiotics; in fact, in some cases the use of antibiotics makes the infection worse. The vast majority of human viral infections can be effectively fought by the body's own immune system, with a little help in the form of proper diet, hydration, and rest. As for the rest, treatment depends on the type and location of the virus, and may include anti-viral or other drugs.

Infection caused by a virus; examples include meningitis and encephalitis.