• An infectious agent that comprises two parts: genetic material and a protein coat. These organisms lack independent metabolism, and they must infect the cells of other types of organisms to reproduce.
  NICHD Pediatric Terminology
  U.S. National Cancer Institute, 2021
• An infectious agent which consists of two parts, genetic material and a protein coat. These organisms lack independent metabolism, and they must infect the cells of other types of organisms to reproduce. Most viruses are capable of passing through fine filters that retain bacteria, and are not visible through a light microscope.
  NCI Thesaurus
  U.S. National Cancer Institute, 2021
• Any infectious agent assigned to the superkingdom Virus.
  CDISC Terminology
  Clinical Data Interchange Standards Consortium (CDISC), 2021
• Group of minute infectious agents characterized by a lack of independent metabolism and by the ability to replicate only within living host cells; have capsid, may have DNA or RNA (not both).
  CRISP Thesaurus
  National Institutes of Health, 2006
• In medicine, a very simple microorganism that infects cells and may cause disease. Because viruses can multiply only inside infected cells, they are not considered to be alive.
  NCI Dictionary of Cancer Terms
  U.S. National Cancer Institute, 2021
• (viruses) Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells.
  NLM Medical Subject Headings
  U.S. National Library of Medicine, 2021
• Viruses are the smallest parasites, typically ranging from 0.02 to 0.3 micrometer, although several very large viruses up to 1 micrometer long (megavirus, pandoravirus) have recently been discovered. Viruses depend completely on cells (bacterial, plant, or animal) to reproduce. Viruses have an outer cover of protein and sometimes lipid,...
  Merck Manuals
  Merck & Co., Inc., 2020