DNA Viruses Virology Short Essay Question And Answers

DNA Viruses Important Notes

1. Herpesvirus Subfamilies:

  • Alpha herpes virus
    • Herpes simplex 1
    • Herpes simplex 2
    • Varicella zoster
  • Beta herpes virus
    • Cytomegalovirus
  • Gamma herpes virus
    • Epstein Burr virus
    • Human herpes type 8

2. Infections caused by Epstein Barr virus

  • Infectious mononucleosis
  • Burkitt’s lymphoma
  • Nasopharyngeal carcinoma

DNA Viruses Short Essays

Question 1. Herpes virus

The Herpes virus belongs to the Herpes viridian family


DNA Viruses Subfamilies

Herpes virus Morphology:

  • Size: 100-200 nm in diameter
  • It contains:
    • Icosahedral caused containing 162 capsomers
    • Double-stranded DNA genome
      • It is surrounded by a lipid envelope containing peplomers
      • The tegument is present between capsid and envelope

Read And Learn More: Microbiology Question and Answers

DNA Viruses Morphology Of Herpesvirus

Herpes virus Laboratory Diagnosis:

  • It includes
    • Collection of specimen
    • Smear preparation
    • Staining of specimen
    • Observation
      • It shows Tzanck cells, Multinucleated giant cells, Cowdry type A intranuclear inclusion bodies
    • Tissue culture
    • Polymerase Chain Reaction

Question 2. Herpes simplex virus?

  • It is a DNA virus
  • It belongs to the herpesviridae family.
  • Man is the only natural host.
  • Herpes simplex virus are two types as follows.
    • Herpes simplex type 1 – is usually associated with oral and ocular lesions.
    • Herpes simplex type 2 – is usually associated with genital infections.
      • Lesions caused by herpes simplex depend on the site of infection, age and immune status of the individual are as follows:
    • Cutaneous infections: These include:
      • Fever
      • Blisters on the cheeks, chins around the mouth, (or) on the forehand
      • Napkin rash on the buttocks of children, – Herpetic widow in medical professionals.
    • Eczema herpeticum:
      • The generalized herpetic eruption is seen in children suffering from eczema.
    • Mucosal lesions:
      • Acute gingivostomatitis
      • Recurrent herpes labialis.
    • Ophthalmic lesions:
      • Keratoconjunctivitis
      • Follicular conjunctivitis.
    • Visceral lesions:
    • Nervous system:
      • HSV meningitis,
      • Sacral autonomic dysfunction.
    • Genital lesions:
      • Infection of the cervix, vagina, or vulva (females)
    • Congenital lesions:
      • Subclinical or localised infection of skin mouth or eyes.
      • Besides primary infections, herpes viruses may present as latent infection, reactivation and re- crude scene.

Herpes simplex virus Laboratory Diagnosis:

DNA Viruses Herpes Simplex Virus Laboratory Diagnosis

Question 3. Cytomegalovirus?

  • Cytomegalovirus is included in herpeviridae family.
  • It is a Human Herpes Virus 5 (HHV-5)
  • The virus is shed in urine, saliva, semen, cervical secretions, tears and breast milk.

Cytomegalovirus Pathogenesis:

  • Cytomegalo virus infections are almost always inapperent leading to prolonged latency with occasional re-activation.
    • Congenital infections:
      • Cytomegalovirus can be transmitted transplacentally from a mother with latent infection to the foetus.
      • Infections are asymptomatic at birth (or) it may lead to cytomegalic inclusion disease which is often fatal.
      • Cytomegal inclusion disease is characterised by:
        • Hepatosplenomegaly.
        • Jaundice
        • Thrombocytopenic purpura
        • Haemolytic anaemia
        • Microcephaly.
    • Post Natal Infections:
      • Are usually asymptomatic
      • Clinical disease in adults resembles infectious mononucleosis.
      • It can cause dissemeinated infection in immune-compromised individuals like AIDS patients.

Cytomegalovirus Laboratory diagnosis:

  • Specimens can be obtained from saliva, urine, breast milk, semen etc.
  • The smear shows enlarged cytomegalic cells with large intra-nuclear owl’s eye appearance
  • Inclusions can be demonstrated in the centrifuged de-posits from urine (or) saliva.
  • The virus can be grown in human fibroblast culture detected by ELISA test.

Cytomegalovirus Treatment:

Ganciclovir is the drug of choice.

Question 4. Adenovirus

  • Adenovirus belongs to the Adenoviridae family
  • They replicate in the nucleus of infected cell

Adenovirus Classification:

  • Adenovirus are grouped into
    • Aviadenovirus- Possess avian adenovirus
    • Mastadenovirus- Possess mammalian adenovirus

Adenovirus Morphology:

  • Size- 70-75 nm in diameter
  • It is non-enveloped
  • Contains
    • Icosahedral capsid
    • Double-stranded DNA

Adenovirus Pathogenesis:

  • Adenovirus causes infections of the respiratory tract, eye, GIT and urinary tract
  • The mode of the spread of infections include
    • Conjunctiva
    • Nasal mucosa
    • Faeco-oral spread
  • The incubation period is 5-7 days

Adenovirus Laboratory Diagnosis:

DNA Viruses Adenovirus Laboratory Diagnosis

DNA Viruses Short Question And Answers

Question 1. Smallpox

  • The causative organism of smallpox is the variola virus
  • It was exclusively human infection with no animal reservoir
  • It used to occur in two distinct varieties

1. Florid

  • It is a highly fatal disease
  • Seen in Asia

2. Alastrim

  • It is a mild non-fatal disease
  • Seen in Latin America
  • Variola major caused smallpox
  • Now it has been eradicated
  • Due to which the vaccination of it is now stopped
  • It was last detected in Somalia, in October 1977.
  • On May 8, 1980, WHO announced the global eradication of small pox

Question 2. Name the disease caused by DNA viruses.

DNA Viruses Disease Caused by DNA Viruses

Question 3. Herpes Zoster

  • It is caused by the Varicella Zoster virus
  • It is a disease of old age
  • It occurs in persons who had chickenpox several years earlier

Herpes Zoster Pathogenesis:

  • The virus remains latent in the sensory ganglia
  • Due to a decrease in immunity, this virus gets reactivated
  • It is triggered by some precipitating stimulus
  • It results in the inflammation of the nerve

Herpes Zoster Clinical Features:

  • Skin lesions
  • Neuritic pain- It is severe and persists for weeks or months
  • Unilateral Vesicles
  • Oral manifestations include:
    • Unilateral involvement of skin areas supplied by ophthalmic, mandibular or Maxillary nerves
    • Painful vesicles are present on the buccal mucosa, tongue, pharynx and larynx
    • Vesicles rupture leaving areas of erosion

Question 4. Antiviral agents

Antiviral agents are agents that selectively attack one of the stages of viral replication without harming the host cells.


DNA Viruses Antiviral agents examples

Question 5. Epstein- Barr virus or EB virus

  • Epstein-Barr virus is named after its discoverers Epstein, Barr and Achong in 1964.
  • Infection with the EB virus leads to
    • Latency
    • Periodic reactivation
    • Lifelong persistence
    • Infects B lymphocytes
  • Diseases caused by it are
    • Infectious mononucleosis
    • EBV associated malignancies
      • Burkin’s lymphoma
      • Lymphoma in immuno-deficient persons
      • Nasopharyngeal carcinoma

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