Virus ... A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. [1]

Dec 3, 2025 · Virus, infectious agent of small size and simple composition that can multiply only in living cells of animals, plants, or bacteria. Viruses possess unique infective properties and thus …

Viruses differ from bacteria in several important ways. Viruses are not living organisms; they can only replicate in the cells of a host. By contrast, bacteria are single-celled organisms that can …

Mar 29, 2023 · A virus is a small piece of genetic information in a “carrying case” — a protective coating called a capsid. Viruses aren’t made up of cells, so they don’t have all the equipment …

Apr 12, 2025 · When a virus enters the body, the innate immune system reacts first. This non-specific defense includes barriers like skin, as well as cells that engulf and destroy invaders. If …

2 days ago · A virus is an infectious microbe consisting of a segment of nucleic acid (either DNA or RNA) surrounded by a protein coat. A virus cannot replicate alone; instead, it must infect …

A virus is an ultramicroscopic agent that can only reproduce in living cells and is spread through infection. Many viruses cause diseases as part of their reproduction process.

Viruses are microscopic biological agents that invade living hosts and infect their bodies by reproducing within their cell tissue. Viruses are tiny infectious agents that rely on living cells to …

VIRUS definition: 1. an extremely small piece of organic material that causes disease in humans, animals, and plants…. Learn more.

Viruses are the smallest of all the microbes. They are said to be so small that 500 million rhinoviruses (which cause the common cold) could fit onto the head of a pin. Viruses vary in …