Virology for competitive examinations

virus2Dr. Sabitha Vijayan BHMS, MD

Interferon – antiviral substances, it is a family of host coded proteins produced by cells on induction by viral or non viral substances
Pox virus:- small pox- last detected case of small pox – sarban devi , a bengladeshi woman on 24th may 1975.


  • Herpes simplex virus  type I causes oral and cutaneous lesions spreading by direct contact
  • Herpes simplex type II causes genital tract infection transmitted venerally.
  • Occupational variety of cuteneous lesion is herpetic whitlow seen in doctors, nurses and dentists.

Eczema herpeticum
Generalized eruption occurs in children suffering from eczema
Crops of vesicles appear around the ulcer;clinically indistinguishable from vaccinia virus infections . both designated as Kaposi’s varicella form eruptions.

In chicken pox eruptions are centrifugal in distribution. (small pox rashes are centripetal in distribution)

In chicken pox patients , secondary bacterial infection due to streptococci or staphylococci occurs. This is called Reyes syndrome. Clinically characterized by acute hepatic failure, encephalopathy and hypoglycemia.

Herpes zoster (syn; shingles, zona)

  • Occurs in patients affected with chicken pox years later.
  • Ramsay hunt syndrome:- rare form of zoster affecting facial nerve with eruption on areas of tympanic membrane and external auditory canal with facial palsy.

Epstein – Barr virus
Causes IMN (infectious mono nucleosis)

Associated with

  • Burkitt’s lymphoma
  • Immunodeficiencies
  •  Naso pharyngeal carcinoma

IMN (glandular fever) – acute self limited illness seen in non immune adults following primary infection with EB virus. Incubation period is 4- 8 weeks . standard diagnostic test is Paul –  Bunnel test

Adenovirus causes respiratory infection , usually picorno virus includes

–  enterovirus –  coxachie virus and polio virus

Poliomyelitis is mainly 3 types

  1. Minor illness :- called abortive polio with head ache, sore throat, and malaise
  2. Non paralytic illness:- it does not progress beyond asceptic meningitis
  3. 5-10% causes paralytic polio

Vaccine:- 2 types

a.     Salk’s killed polio vaccine

b.     Live polio vaccine is oral polio vaccine

  • Orthomyxovirus causes influenza.
  • Paramyxovirus  Eg. Mumps virus
  • Measles (Rubiola) – genus morbiliform virus
  • Multinucleated giant cells called Warthin – Finkelclay cells are found in lymphoid tissue of patients.
  • Koplik’s spots developon buccal mucosa two or three days before the appearance of rash.


  1. Japanese encephalitis (vector- culex tritaneorynchus)
  2. Yellow fever – Vector – Aedes aegypti
  3. Dengue fever –  Vector  – Aedes aegypti

Tick borne encephalitis eg. KFD (Kyansur forest disease)

 Eg. Rabies virus  causes hydrophobia

  • Diagnosis is confirmed by negri bodies (inclusion bodies) in brain in post mortem examination mostly in hippocampus and cerebellum
  • PAPOVA virus include papilloma virus group and polyoma virus group.
  • The common human disease produced by papova virus is papilloma or wart. (verruca vulgaris)
  • A special type of wart is condylom accuminatum or genital wart found on external genitalia. This may be transmitted venerally and may occasionally turn malignant.
  • Parvo virus cause erythema infectiosum –‘the fifth disease’ a contagious disease of children characterized by erythematous rash first appearing on cheeks. – slapped cheek appearance.


  1. Caused by genus rubivirus of family toga viridae
  2. Koplik’s spot absent
  3. Rash is discrete and coalesce and disappear on 3rd day
  4. Non tender enlargement of post cervical glands is characteristic
  5. If Rubella occurs in early pregnancy, the foetus may die
  6. Congenital malformations are common during first trimester.
  7. Infected babies constitute an important source of infection for about 6 months (virus may persist for years in tissues such as cataractous lenses)
  8. Diagnosis of Rubella in early pregnancy is an indication for therapeutic abortion.
  9. Cruzfelt – Jacob disease is sub acute encephalopathy with progressive incoordination and dementia caused by group b prion virus.

Haemorrhagic fever with renal syndrome(HFRS)- also known as epidemic haemorrhagic nephrosonephritis is caused by Huntaan virus of family Bunya viridae.

HIV – human immunodeficiency virus – retro virus now called Human T cell lymphotrophic virus

  • RNA virus attacks CD4 cells.
  • A. Envelops antigens – 1. spicks antigen, 2. transmembrane
  • B. Shell antigen
  • C. Core antigen
  • D. Polymerase antigen

            Incubation period varies from 2-6 weeks to 15 years.

Features characaterising AIDS

  • 1.     Lymphopenia
  • 2.     Selective T cell deficiency – reduction in numbers of T4 (CD4) cells, inversion of T4: T8 ratio
  • 3.     Decreased delayed hypersensitivityon skin testing
  • 4.     Hypergammaglobulinaemia – predominantly IgG and Ig A; also IgM in children.
  • 5.     Polyclonal activation of B cells an dincreased spontaneous spontaneous secretion Ig.
  • Common malignancies associated with HIV infection is Kaposi’s sarcoma and lymphoma- hodgkin’s and Non hodgkin’s types.

HIV- Elisa for detection :  Western blot for confirmation

Ergotoxicosis (ergotism) is due to claviceps purpura growing on fruiting heads of rye.


            Hepatitis A – incubation period  –   2- 6 weeks

            Hepatitis B  – I P                                     4 – 8 weeks

            Hepatitis C  –      I P                                2 – 22 weeks

            Hepatitis D         I p                                4 – 8 weeks

            Hepatitis E          I P                               2 – 9 weeks

  1. Hepatitis B – DNA virus ; all others are RNA virus
  2. Spreads by faeco oral route –  hepatitis A and E
  3. Spreads by percutaneous route –  Hepatitis B,C and D
  4. Hepatitis B also spread by vertical and sexual route
  5. Oncogenicity present in Hepatitis B especially after neonatal infection.
  6. Carrier state present in Hepatitis B only
  7. Hepatitis B virus may present in blood and other body fluids and excretions such as saliva, breast milk,semen, vaginal secretions, urine , bile etc.
  8. Feces not known to be infectious
  9. HBs Ag is the first viral marker to appear in blood after infection; it remains in circulation throughout icteric course of disease. In a typical case it disappear within roughly 2 months but may last for 6 months.
  10. HBsAg is not demonstrable in circulation but antibody, antiHBe appear in serum a week or two after appearance of HbSAg
  11. So anti-HbeAg is the antibody marker to be seen in blood.
  12. HBeAg (HB envelop antigen) appears in blood concurrently with HBsAg. HbeAg is an indicator of intrahepatic viral replication and its presence in blood indicates high infectivity.
  13. For diagnosis of HBV infection, simultaneous presence of IgM, HBC indicates recent infection and presence of IgG ;anti H-Be indicates remote infection.
  14. Type E hepatitis : enterically transmitted.
  15. Non A – non B hepatitis caused by Hep. C virus

Inclusion body inviruses

a.     Intracytoplasmic

Guarnieri body –  Varicella, Vaccinia

Negri body – Rabies

Henderson – Paterson body –  Molluscum contagium

  • b. Intranuclear
  • a. Lipschutz bodies –  herpes fibrilis, herpes zoster, varicella
  • b. Councilmann’s bodies –  yellow fever, virus B encephalitis
  • c. Nicolau’s bodies – herpes fibrilis, herpes zoster , polio, Rift valley fever

Association of virus with human cancer

Virus family Virus genus Human cancer
Herpes virus E-b Virus Nasopharyngeal carcinomaAfrican Burkitt’s lymphomaB- cell lymphoma
Herpes 2 virus Cervical carcinoma
Papova viridae Papilloma virus Urogenital tumourSquamous cell carcinoma
Hepadne virus Hep B virus Primary Hepatocellular carcinoma
Retrovirus HTL virus Adult T Cell Leukaemia

 Viral infections associated with associated with maculopapular rash

  1. Adenovirus infection
  2. Arbovirus infection
  3. Measles
  4. Cytomegalovirus infections
  5. Enterovirus
  6. Hep-B virus
  7. IMN (kissing disease)
  8. Rubella
  • Haemolytic uraemic syndrome caused by virotoxin producing e-coli
  • Brazilian purpuric fever caused by Haemphilus aegypticus
  • Cryptospridum causes diarrhea
  • Cat scratch disease is caused by cat scratch bacillus


Superficial mycosis(cutaneous ) or dematophytis

  1. Microsporum –  attacks skin and hair ; not nail
  2. Tricophyton attacks skin , hair and nails. Most important human parasites are T. rubrum and T. tonsuran
  3. Epidermophyton  – e.floccosum attacks skin and nails but not hair.


  • Tinea capitis – ring worm of scalp
  • Tinea circinata – ringworm of glabrous skin
  • Tinea barbae –  ringworm of beard
  • Tinea pedis – Athletes foot
  • Tinea cruris – Dhobi itch or Jock itch
  • Tinea unguum  – ring worm of nails

Systemic mycosis

  • Candid albicans – yeast like fungi
  • Histoplasma capsulatum –  Darling’s disease
  • Cryptococcus neoformans – yeast
  • Aspergillus  –  fungus ball
  • Cocciodes immitis – desert rheumatism

 All rights reserved @ similima

Be the first to comment

Leave a Reply

Your email address will not be published.