Intro

• Virology is the science that deals with the discovery, isolation, identification, characterization, pathogenicity, pathogenesis, and classification of viruses
• Viruses are microscopic infectious agents that invade cells and eventually cause disease
• Viruses are particles of nucleic acid (DNA or RNA) covered by a protein coat
• Viruses may use an animal, plant, or bacterial host to survive and reproduce
• Viruses rely on living cells to multiply and can evolve and mutate
• Viruses are obligate intracellular parasites that require a host to cause damage
• Viruses do not metabolize energy, grow, or undergo cell division
• Viruses need to be inside a host for energy production and protein synthesis
• Viruses are considered non-living, acellular, and lack organelles
• Viruses cannot carry out all life processes, such as reproduction, growth, division, and energy transformation
• Viruses need a specialized electron microscope to be viewed, unlike bacteria and other cells that can be seen with light microscopes
• Virions are complete virus particles made up of nucleic acid and protein, which can induce disease conditions in animals, plants, and humans
• Viroids contain RNA only and are associated with plant diseases like Bean mosaic virus and Wound tumor virus
• Prions are protein particles that do not contain nucleic acid and are associated with diseases like mad cow disease and chronic wasting disease
• Historically, diseases caused by viruses like rabies have been documented since the 4th Century by Hippocrates
• The birth of virology was by Adolf Mayer, who researched tobacco mosaic disease and demonstrated the first experimental transmission of a viral disease of plants
• In 1892, Russian scientist Dmitri Ivanovsky detected the Tobacco Mosaic virus, marking the formal discovery of viruses
• Dutch scientist Martinus Willem Beijerinck, along with Ivanovsky, is considered a founder of Virology
• General characteristics of viruses:

  • Very small agents that can't be seen ordinarily and require an electron microscope
  • Contain one type of nucleic acid (RNA or DNA)
  • Multiply by replication of their nucleic acid
  • May be surrounded by a lipid-containing envelope
  • Don't carry enzymes, grow on synthetic media, or have ribosomes and organelles
  • Can pass through filters that bacteria can't
  • Antibiotics have no effect on viruses, but they are sensitive to interferon
  • Some viruses can cause latent infections