virus

• Diseases caused by DNA Viruses


  • Hepatitis
  • Herpes
  • Chickenpox
  • Shingles
  • Infectious Mononucleosis
  • Congenital CMV infection
  • Gastroenteritis
  • Hepatitis
  • Conjunctivitis
  • Respiratory infection
  • Cervical cancer
  • Genital warts
  • Oropharyngeal cancer
  • Fifth disease
• Hepadnavirus


  Causes Hepatitis B, can lead to liver cancer
• Herpesvirus


  Causes cold sores, genital herpes, chickenpox, shingles, infectious mononucleosis
• Poxvirus


  Causes Monkeypox, Smallpox, Vaccinia
• Adenovirus


  Causes gastroenteritis, hepatitis, conjunctivitis, respiratory infection
• Papillomavirus


  Causes cervical cancer, genital warts, oropharyngeal cancer
• Polyomaviruses


  JC polyomavirus, BK polyomavirus, Merkel cell polyomavirus
• Parvovirus


  Causes Fifth disease or Erythema Infectiosum
• Calicivirus


  Causes acute viral gastroenteritis (Norovirus)
• Picornavirus


  Includes enteroviruses like rhinoviruses and poliovirus, causes poliomyelitis
• Togavirus


  Causes Chikungunya, Rubella
• Flavivirus


  Causes Dengue fever, Yellow fever, Zika, West Nile fever
• Coronavirus


  Causes COVID-19, Severe Acute Respiratory Syndrome (SARS) , Middle east respiratory syndrome (MERS)
• Rhabdovirus


  Causes Rabies
• Orthomyxovirus


  Influenza Virus (A, B, C)
• Arenavirus


  Causes Lassa fever, Argentine hemorrhagic fever
• Bunyavirus


  Causes Hantavirus Pulmonary Syndrome, Hemorrhagic Fever with Renal Syndrome, Rift Valley Fever, Crimean-Congo Hemorrhagic Fever
• Filovirus


  Causes Ebola Virus Disease, Marburg Virus Disease
• Paramyxovirus


  Causes Measles, Mumps, Respiratory Syncytial Virus
• Reovirus


  Causes common gastroenteritis in young children (Rotavirus)
• Retrovirus


  Human Immunodeficiency Virus (HIV) can cause AIDS
• Virus


  Infectious particle that can reproduce only by infecting a host cell (plants, animals, or humans)
• Virus


  • Obligatory intracellular parasite
  • Not considered "living"
  • Do not have cells
  • Smaller than cells (20 – 300 nanometers)
  • Reproduces by infecting a host cell and using its machinery to make more viruses ("reprogramming host cells to become virus-making factories")
  • Very diverse
  • Different shapes & structures
  • Different kinds of genomes
  • Infect different hosts
• Bacteriophage


  Viruses that infect bacteria
• Virus


  Infectious particle that can reproduce only by infecting a host cell (a total parasite)
• Virus genome


  Genetic material made up of nucleic acid (RNA or DNA, double- or single-stranded)
• Virus capsid


  Protein shell that surrounds the virus genome
• Virus envelope


  Lipid membrane surrounding the entire capsid, helps viral particles bind to host cells
• Capsomer


  Made up of protein molecules
• Virus Capsid (Protein Shell)


  • Icosahedral - 20-sided shape
  • Filamentous / Helical - thin, linear, thread-like, rod or helical
  • Head-tail / Complex - combined icosahedral & filamentous
• Virus Life Cycle


  1. Attachment

  2. Entry

  3. Genome replication & Gene expression

  4. Assembly

  5. Release
• Attachment


  • Recognition & binding to a host cell via a receptor molecule on the cell surface
  • A specific protein on the virus capsid binds to a specific molecule on the membrane of the host cell (protein receptor)
  • A cell w/o receptors for a virus can't be infected by that virus
• Entry


  • Virus or its genetic material enters the cell
  • Through fusion w/ the membrane (enveloped viruses)
  • Endocytosis (non-enveloped viruses)
• Genome replication & Gene expression


  • Viral genome is copied & its genes are expressed to make viral proteins
  • Viruses must encode capsid proteins, envelope proteins & other proteins for replication
• Assembly


  • New viral particles are assembled from the genome copies & viral proteins
  • Newly synthesized capsid proteins come together to form capsomers eventually forming a full-sized capsid
• Release


  • Completed viral particles exit the cell & can infect other cells
  • Lysis (cell burst)
  • Exocytosis
  • Budding
• Virus Classification


  • Nucleic Acid: DNA / RNA
  • Capsid shape: Icosahedral / Helical / Complex
  • Envelope: Naked / Enveloped
  • Genome architecture: single-stranded (ss) / double-stranded (ds)
• Poxviridae - large dsDNA icosahedral viruses that cause skin lesions & systemic disease
• Herpesviridae - small dsDNA icosahedral viruses that cause cold sores & chickenpox
• Adenoviridae - medium ssDNA icosahedral viruses that cause respiratory tract infection