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Friday, February 22, 2013

Herpes Virus: Properties, Classification, Diseases, Varicella Zoster Virus

Herpes virus: 

Get to know Herpes virus, its classification, types, usual sites of infection, sites of latency, the diseases caused by herpes virus and their routes of transmission.  Also do you know what is herpes B virus?

Herpes virus is a double stranded DNA enveloped virus.
Structure of Herpes Virus

Properties of herpes virus:

  1. Virion: Spherical
  2. Genome: Double stranded linear DNA
  3. Capsid: Icosahedral
  4. Replication: Occurs within the nucleus and form intranuclear inclusions.
  5. Envelop: The only virus that develops envelop (lipoprotein envelop) from the nuclear membrane by budding.
  6. Enzyme: No viral polymerase enzyme. Uses host cell RNA polymerase.
  7. Serotype: Single.
  8. Size: large, 120-200 nm diameter. Second in size to poxvirus.
  9. Latent infection: Noted for their ability to cause latent infection. In such cases, the acute infection is followed by a period of asymptomatic period during which the virus is in acquiescent (latent) stage. When the patient is exposed to an inciting agent or immunosuppression occurs then reactivation of virus replication and disease can occur. ( Acute disease > asymptomatic period > latent state)
  10. Sensitivity: Ether sensitive.
  11. Giant cell: All produce giant cells.


Classification and disease of herpes:

There are 8 types of herpes virus and they belong to 3 subgroups according to the type of cell they mainly infect and their site of latency:


Sub group  
Type  
Usual site of infection  
Site of latency  
α subgroup
Herpes simplex virus 1 (HSV 1)
Epithelial cells
Cranial sensory ganglia

Herpes simplex virus 2 (HSV 2)
"
Lumbar or sacral ganglia

Human herpes virus 3 ( Varicella Zoster Virus)
"
Cranial or thoracic sensory ganglia




Lymphotropic β subgroup virus
Human herpes virus 5 ( Cytomegalo virus)
Variety of cells
Variety of cells

Human herpes virus 6
"
"

Human herpes virus 7
"
"




γ subgroup
Human herpes virus 4 (Epstein-Barr virus)
Lymphoid cells
(mainly B lymphocytes)
Lymphoid cells mainly lymphocytes

Human herpes virus 8
Vascular endothelial cells
Uncertain



The diseases and routes of transmission of Herpes Virus:

Herpes Virus
Disease (Primary infection)
Disease (Recurrent infection)
Routes of transmission
HHV 1
(Herpes Simplex Virus 1)
Gingivostomatitis
  • Herpes labialis
  • Encephalitis
  • Keratitis

  • Respiratory secretions
  • Saliva 
  • Direct contact with lesion

HHV 2
 (Herpes Simplex Virus 2)
  • Genital herpes (herpes genitalis)
  • Perinatal disseminated disease (Neonatal- herpes)

Genital herpes
  • Sexual contact
  • Perinatal infection

HHV 3 
( Varicella Zoster Virus)
Varicella (Chicken pox) – in children
Zoster (Shingles) – in adults.
  • Varicella: By respiratory droplets and direct contact with the lesion
  • Zoster: Is not transmitted as it is basically the recurrent form of Varicella in adults.

HHV 4 
(Epstein-Barr Virus)
  • Nasopharyngeal carcinoma 
  • Oral hairy cell leukoplakia
  • Burkitt’s lymphoma
  • Infectious mononucleosis
  • Hepatitis

None
  • Respiratory secretions 
  • Saliva, e.g., during kissing

HHV 5 
(Cytomegalo Virus)
  • Congenital infection (in utero)
  • Mononucleosis
  • Hepatitis

Asymptomatic shedding
  • Early life: Placenta, birth canal and breast milk. 
  • Young children: saliva. 
  • Adults: sexual contact. 
  • Others: Blood transfusion and organ transplantation

HHV 6
  • Childhood disease with fever and skin rash (Roseola infantum and sixth disease – a benign rash of infants)
  •  Exanthem subitum



HHV 7
Nonpathogenic and may even be helpful against HIV (Human Immunodeficiency virus)





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What is herpes simiae?

It is an Old World monkey virus that resembles HSV 1 and can cause fatal neurologic disease in animal handlers, usually resulting from animal bite. It is also called Herpes simian B virus, Macacine herpesvirus 1 (formerly Cercopithecine herpesvirus 1, CHV-1), Herpes B virus.


Diseases caused by HSV 1 and HSV 2:

Site of infection
Herpes Simplex Virus 1
Herpes Simplex Virus 2
Skin
Vesicular lesion above the waist
Vesicular lesion below the waist
Mouth
Gingivostomatits
Rare
Eye
Keratoconjunctivitis
Rare
CNS
Encephalitis (temporal lobe)
Meningitis
Neonate
Rare
Skin lesion and disseminated infection
Dissemination to viscera in immunocompromised patients
Yes
Rare


 Varicella zoster virus (VZV):

Disease caused by VZV: Varicella (chicken pox) is the primary disease. Zoster (shingles) is the recurrent form.
Properties of VZV:

  1. VZV is structurally and morphologically identical to other herpes virus but its antigenicity is different
  2. It has a single serotype
  3. Humans are the natural host
  4. Transmission by respiratory droplet and direct contact
  5. Infect mucosa of urinary tract via blood to the skin


Stages of Chicken Pox
Varicella / Chicken Pox:

  • Incubation Peroid: 14-21 days
  • Rash: Papulovesicular rash that appears in crops on the trunk and spread to head and extremities.
    The rash evolves from papules to vesicle, pustules and finally crust. Itching is common when vesicle are present
  • Complication: Varicella pneumonia, encephalitis, Reye’s syndrome (Encephalitis with liver degeneration)


Chicken Pox



Shingles
Zoster / Shingles:


  1. Painful vesicle along the course of a sensory nerve of the head or trunk
  2. Pain can last for weeks and post-zoster neuralgia (post-herpatic neuralgia) can be debilitating.
  3. In immunocompromised: Life threatening disseminated infection such as pneumonia can occur.
   




To know more about Varicella Zoster Virus and Chicken Pox / Shingles read:





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2 comments:

  1. Try a zinc gluconate topical on the HSV-2 lesions. It will heal the skin naturally and stop the itching.

    ReplyDelete

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