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Herpes Simplex Virus (HSV)

The herpes virus family consist a large variety of virus species that cause infections in humans as well as animals. They contain double stranded DNA genome. These viruses are generally enveloped and have the ability to replicate inside the host cells. They are susceptible to alcohol, ether, chloroform, etc. The Herpesviridae is divided into three subfamilies based on biological, physical and genetic properties; alpha herpes, beta herpes and gamma herpes virus. Out of the three, the Varicella zoster virus is the most important one coming under alpha herpes.

The HSV naturally occurs in humans. They are of two types; type I and type II. Type I is transmitted through contact and droplet infection. Type II is usually involved in genital infections spread venereally. Primary infection by Herpes Simplex is usually acquired during two to five years of age and is self limiting. The sources of infection include saliva, lesions from skin and secretions of the respiratory tract. Genital infection creates asymptomatic carriers. The virus enters the body through skin and mucosa, multiplies locally and spreads from one cell to another. The virus enters the cutaneous nerve fibers and gets transported to the ganglia and there replication occurs. Inside the ganglia the virus remains dormant, and causes intermittent oral and genital lesions. Antibodies are produced in these infections which reduces the severity of clinical manifestation.

The lesions are typically thin walled with breaking down roofs and slowly recovering into small ulcers on the surface of the skin.

Clinical features of the viral infections shows off as different types;

1. Mucosal: mucosa of the buccal cavity is the most infected place.
2. Cutaneous: face, cheeks, region around the mouth and forehead are the most frequent sites. In infants, lesions also seem to appear on the buttocks. The typical lesions are called ‘fever blister’.
3. Ophthalmic: corneal blindness, acute keratoconjunctivitis and follicular conjunctivitis are common. Chorioretinitis and acute necrotizing retinitis are not so common but are really serious conditions.
4. Nervous system: HSV encephalitis is the commonly occurring neurological condition and occurs along with fever.
5. Visceral: esophagitis, sub-sternal pain, weight loss, tracheobronchitis, pneumonitis, etc. are the HSV infections of the visceral region.
6. Congenital: the mother with congenital HSV type II infection having genital lesions may transfer it to the child during birth. Eyes, mouth and skin are affected in neonatal herpes. These are fatal and survivors suffer from neurological mutilation.
7. Genital: penis is the main organ where lesions appear in case of men. Urethritis is also seen among some. In the case of women; cervix, vagina, vulva and perineum are seem to be affected. In homosexuals, rectal and perineal lesions are seen.

Serological methods for the detection of antibodies such as ELISA, neutralization test, complement fixation test, etc. are found to be useful. Fluorescent antibody technique is done for the isolation of herpes virus antigen. PCR based DNA detection is also done in certain laboratories.

Idoxuridine, used for treating eye and skin infections was one of the first drugs that were found to be clinically active against the virus. Deep systemic infections were cured by the administration of acyclovir and vidarabine. Encephalitis outcome has been improved when acyclovir was intravenously administered in the early stage. Valaciclovir and famciclovir are effective oral representatives.

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