VIROLOGY

• What are the key classifications of viruses based on their structure?

  • Nucleic acid composition: DNA or RNA
  • Strandedness: Single or double stranded
  • Capsid structure: Helical or icosahedral
  • Envelope: Presence or absence
• What type of specimens are suitable for viral culture?


  Aspirated secretions or swabs.
• How should samples for viral culture be handled?

  Samples should be kept moist and cultured immediately.
• What is the recommended storage temperature for specimens?

  Refrigerate at 4°C.
• What is the purpose of using viral transport medium?

  To protect unstable viruses during transport.
• What types of specimens can be collected for viral testing?

  1. Throat swabs or washings
  2. Rectal swabs
  3. Skin scrapings or lesion swabs
  4. Urine
  5. Body fluids or vesicles
  6. Tissue biopsies
• What is the most rapid method of viral diagnosis?

  Electron microscopy.
• What is the most common method for rapid electron microscopy?

  Negative staining technique.
• What are the characteristics of the Adenoviridae family?

  • dsDNA genome
  • Icosahedral capsid
  • no envelope
  • approx. 50 human serotypes
• What is the genome type of Herpesviridae?

  Partly dsDNA genome.
• What are the types of Herpesviridae known?

  1. Herpes simplex virus type 1 (HSV-1)
  2. Herpes simplex virus type 2 (HSV-2)
  3. Varicella-zoster virus (VZV)
  4. Epstein-Barr virus (EBV)
  5. Cytomegalovirus (CMV)
  6. Human herpesvirus 6 and 7 (HHV-6 and HHV-7)
  7. Human herpesvirus 8 (HHV-8)
• What is the primary disease caused by Varicella-zoster virus?

  Chickenpox (varicella) and shingles (zoster).
• What is the characteristic of Cytomegalovirus (CMV) infection?

  Asymptomatic infection in healthy individuals, but can cause severe disease in immunocompromised patients.
• What are the characteristics of Papovaviridae family?

  • DsDNA genome
  • Icosahedral capsid
  • No envelope
• What is the only human parvovirus?

  Parvovirus B-19.
• What are the characteristics of Poxviridae family?

  • DNA genome
  • Largest and most complex of all viruses
  • Brick-shaped virion with non-conforming symmetry referred to a complex
  • dsDNA genome
• What viruses are caused by Poxviridae?

  Smallpox, orf virus and molluscum contagiosum.
• What are the characteristics of Arenaviridae family?

  • Enveloped
  • irregular-shaped capsid containing two-segmented ssRNA genome
• What are the characteristics of Bunyaviridae family?

  • Segmented ssRNA genome
  • Spherical or pleomorphic capsid with envelope
• What is the primary disease associated with Lymphocytic choriomeningitis virus (LCMV)?

  Lymphocytic choriomeningitis.
• What are the characteristics of Caliciviridae family?


  • Non-enveloped
  • Icosahedral capsid surrounding ssRNA genome
• What are common diseases caused by Norwalk virus?

  Nausea, vomiting, and diarrhea.
• What are the characteristics of Coronaviridae family?

  • Enveloped
  • Helical capsid with ssRNA genome
• What are the characteristics of Filoviridae family?

  • Enveloped
  • Long filamentous and irregular capsid forms with ssRNA genome
• What diseases are associated with Ebola virus?

  Ebola hemorrhagic fever.
• What are the three major antigenic types of Orthomyxoviridae?

  Influenza A, B, and C.
• STEPS IN VIRAL REPLICATION CYCLE

  1. Attachment and penetration
  2. Uncoating
  3. Early mRNA and protein synthesis
  4. Viral genome replication
  5. Late mRNA and protein synthesis
  6. Assembly of virion
  7. Release
• Classification based on

  • Presence or absence
  • Acquired from nuclear or cytoplasmic membrane
  • Envelope
• Classification based on

  • DNA/RNA
  • Single or double stranded


  Nucleic acid composition
• Buffered isotonic solution with a protein, such as albumin, gelatin, or serum

  Viral transport medium
• Respiratory swab and tissue samples usually use viral transport medium to protect less stable viruses; sometimes with antibiotics to inhibit contamination but not for Blood bone marrow, CSF, amniotic fluid, urine, pericardial fluid, and pleural fluid.
• Refrigerate viral specimen at 4C with delay; if longer than 4 days freeze at 70C
• Storage temp. for viral specimen

  4 degrees Celsius
• Temp. in transporting viral specimen

  -70 degrees Celsius
• Lab tests for viral samples

  1. Electron microscopy
  2. Culture
  3. Serologic tests
• Causes pharyngitis, pharyngocojunctival fever, keratoconjunctivitis, pneumonia, hemorrhagic cystitis, disseminated disease and gastroenteritis in children.

  Adenovirus
• Characteristics of Hepadnaviridae

  • Partly dsDNA genome
  • Icosahedral capsid w/ envelope
  • virion (Dane particle)
  • surface antigen (Australia antigen)
• Acute infection with resolution (90%); fulminant hepatitis most co-infected with delta virus (1%); chronic hepatitis, persistence of HBsAG (9%) followed by resolution (disappearance of HBsAG), asymptomatic carrier state, chronic persistent (systemic disease without progressive liver disease) or chronic active liver disease (progressive liver damage)

  Hepatitis B Virus
• Characteristics of Herpesviridae

  • dsDNA genome
  • icosahedral capsid w/ envelope
  • at least 8 human herpes viruses known
• Gingivostomatitis, pharyngitis, herpes labialis, conjunctivitis, keratitis, encephalitis

  Herpes simplex virus type 1 (HSV-1)