TORCH group of infections - Herpes simplex virus

Depending on immunological and clinical differences two types of herpes simplex viruses can be distinguished.

Type 1(HSV 1):

It is responsible for most nongenital herpetic infections.

But up to half of new cases of adult genital herpes are caused by HSV 1.

Type 2(HSV 2):

It is recovered almost exclusively from the genital tract.

Sexual contact is the main mode of transmission.

Maternal infection:

HSV 2 infections can be categorized into 3 types:

-Primary infection: No presence prior antibodies to HSV 1 or HSV 2.

-Nonprimary first episode: Newly acquired HSV 2 infection with preexisting HSV 1 cross-reacting antibodies.

-Recurrent infection: Reactivation of prior HSV 2 infection in the presence of HSV2 2 antibodies.

Primary infection:

-Among newly acquired primary HSV 2 genital infections only one third are symptomatic.

-Incubation period: 3 to 6 days.

-Clinical features: Papular eruption follows with itching and tingling.

-The eruption then becomes painful and vesicular with multiple vulvar and perineal lesions that may coalesce.

-Severe inguinal adenopathy may occur.

-Transient systemic influenza like symptoms caused by viremia.

-Hepatitis, encephalitis, pneumonia etc may develop.

-Usually by 2 to 4 weeks all signs and symptoms of infection will disappear.

-Cervical involvement can occur but may not cause clinical symptoms.

-Some cases may require hospitalization.

Nonprimary first infection:

-Previously existing HSV 1 antibody can give partial protection.

-They may present as first clinical infection but symptoms will be less severe.

-They will have fewer lesions, less systemic manifestations, less pain, briefer duration of lesion and viral shedding.

-Sometimes difficult to distinguish with primary infection.

Recurrent infection:

-In latency period viral particles recide in nerve ganglia. They can get reactivated.

-It is called recurrent infection and virus shedding occurs during this.

-The lesions will be fever in number, less painful and shedding of the virus will be for shorter periods (2 to 5 days).

-Usually recurrence will be at the same site.

Sub clinical shedding occurs in around 60% of women with history of genital herpes infection.

Many sexually transmitted cases occur due to sub clinical shedding. Its effect on pregnancy has yet to be determined.

Neonatal infection:

-Vertical transmission through placenta or membranes is rare.

-Usually the fetus will get infection by contact with virus shed from cervix or lower genital tract during birth.

Newborn infection presents as:

-Disseminated wit involvement of major viscera.

-Localized with involvement confined to central nervous system, eyes, skin, mucosa etc.

-Asymptomatic.

With primary maternal infection 50% risk of neonatal infection is there.

With recurrent infection the risk decreases to 0 to 5%.

This could be due to smaller viral load in maternal secretions and transplacentally   acquired antibody, which will decrease the severity and incidence of the disease.

Localized infection will be usually associated with good outcome.

But disseminated infection, even when treated with acyclovir or vidarabine can result in around 50% mortality rate.

In at least half of the survivors serious ophthalmic and central nervous system damage can occur.

Diagnosis:

-Tissue culture is optimal to confirm apparent infection and asymptomatic recurrences.

-The tissue should be taken from lesions before they undergo crusting, then it will give 95% of sensitivity.

-Tzanck smear: cytological examination after alcohol fixation and papanicolaou staining. It is having 70% sensitivity.

-Using PCR increases HSV detection by four to eight fold compared to culture.

Management:

-Antiviral therapy with acyclovir, fansciclovir and velacyclovir are used to treat first episode of genital herpes in non pregnant and pregnant women.

-In recurrent infections and to reduce heterosexual transmission the drugs can be used as suppressive therapy.

-Intense discomfort can treated with analgesics and topical anesthetics.

-Severe urinary retention may need catheterization.

-Trails are going on to keep acyclovir or valacyclovir as suppressive therapy during last month of pregnancy to prevent recurrence nears term.

-It reduces signs and symptoms of recurrent infection but does not completely eliminate asymptomatic viral shedding.

-Cesarean delivery is indicated to those with active genital lesions or in those with a typical prodrome of an impending outbreak.

 -So if primary or recurrent lesions visualized near the time of labor cesarean to be done irrespective of the time of rupture of the membranes.

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