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

To know more about HSV 1 and HSV2 read:

• Herpes Simplex Virus: Sign and Symptoms, Complications, Diagnosis, Treatment and Prevention of Herpes 1 and 2

 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:

1. Varicella Zoster Virus(VZV): Chicken Pox and Shingles, Properties, Transmission, Pathogenesis and Immunity

2. VZV: Sign and Symptoms of chicken pox and shingles, Diagnosis, Treatment and Prevention

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