Virology

• What does the term "virus" mean in Greek?

  Poison
• Who initially described the virus in 1798?

  Edward Jenner
• What is a virus primarily composed of?

  A package of genetic information protected by a protein shell
• What types of nucleic acid can viruses contain?

  DNA or RNA
• What do viruses lack that distinguishes them from cellular organisms?

  Nuclear membrane and external cell wall
• Why are viruses considered parasites?

  They rely on host cells for replication
• What are the three basic forms of viruses?

  1. Complex

  • Poxviruses: No capsid, DNA surrounded by core membrane
  • Bacteriophages: Complex capsid head and tail structures

  1. Naked or non-enveloped: Capsid containing DNA or RNA
  2. Enveloped:

  • Outer membrane
  • Capsid containing DNA or RNA
• What are capsomeres?


  Structural subunits containing several proteins
• How do capsomeres contribute to viral structure?

  They aggregate to produce the viral capsid
• What is a nucleocapsid?


  The association of the viral capsid with the viral nucleic acid
• What are lipid envelopes derived from?

  Cellular membranes
• What types of cells can viruses infect?

  Every cell type
• What size range do viruses typically fall into?

  20 - 200 nm
• What is a characteristic of viruses regarding metabolic enzymes?

  They do not have metabolic enzymes
• What machinery do viruses lack for protein production?

  They lack machinery for protein production
• What instructions do viruses have regarding reproduction?

  Instructions for their own reproduction, but only inside a host cell
• What factors are used for viral classification?

  • Shape
  • Type and form of nucleic acid
  • Enveloped or naked
  • Mode of replication
  • Organization of the genome and antigenic differences
• What is the hierarchical classification of viruses?


  Order - Family - subfamily - genus - species - strain/type
• What suffix do all viral families have?

  Viridae
• What suffix do genera of viruses have?

  Virus
• What are the types of RNA viruses?

  1. RNA single stranded: positive polarity or negative polarity
  2. RNA double stranded: one piece or segmented
• What are the types of DNA viruses?

  1. Single stranded
  2. Double stranded
• What are the types of viral tropisms?

  1. Restricted: e.g., Human liver cells – hepatitis B
  2. Intermediate: e.g., Intestinal and nerve cells of primates - poliovirus
  3. Broad: e.g., Various cells of all mammals – rabies
• How can viral infections be acquired?

  • Direct personal contact: Herpes viruses, HIV, Influenza
  • Airborne spread: Chicken pox
  • Parenteral: HIV, Hepatitis B and C, cytomegalovirus (CMV)
  • Fomites: Enteroviruses and other sturdy drying resistant viruses
  • Vectors: West Nile
  • Vertical transmission: HIV, Herpes simplex, cytomegalovirus, rubella (German measles)
  • Enteral (foodborne): Hepatitis A, gastroenteritis viruses
• What are the steps of the viral life cycle?

  1. Adsorption/Docking: Specific interactions
  2. Penetration: Receptor mediated endocytosis, vesicle fuses with lysosome
  3. Uncoating: Enzymes in lysosome digest capsid and release viral genome
  4. Replication: Copies of viral genome and proteins
  5. Assembly: Viral capsid reforms and packages genome
  6. Release: Budding or lytic host cell burst