Viruses are considered by some biologists to be a life form, because they carry genetic material, reproduce, and evolve through natural selection, although they lack some key characteristics, such …

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 that cells do to …

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 often cause …

1 day 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 cells and use …

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 the virus gets …

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 multiply. They may …

Viruses are typically described as obligate intracellular parasites, acellular infectious agents that require the presence of a host cell in order to multiply.