INTRODUCTION TO HERPES SIMPLEX VIRUS (HSV)
Herpes Simplex Virus causes the most common viral infection in human and worldwide in distribution.
The herpes simplex virus is of two types –
- HSV type 1 (human herpesvirus type 1 or HHV type 1)
- HSV type 2 (human herpesvirus type 2 or HHV type 2)
Herpes Simplex Virus type 1 is usually associated with oral and ocular lesions, while type 2 is responsible for the majority of genital infection.
DISEASES CAUSED BY HERPES SIMPLEX VIRUS (HSV)
⇒ HSV type 1 causes
- Acute Gingivostomatitis
- Herpes labialis
⇒ HSV type 2 causes
- Genital herpes
- Neonatal herpes
- Aseptic meningitis.
PATHOGENESIS OF HERPES SIMPLEX VIRUS (HSV)
⇒ The sources of infection are Saliva, Skin lesions or Respiratory Secretions. Primary infection is usually acquired in early childhood, between 2-5 years of age.
Transmission occurs by close contact and maybe
venereal in genital herpes.
Virus enters through defects in skin or
mucous membranes & multiply locally.
Virus enters Cutaneous nerve fibers & is
transported to ganglia where it replicates.
Migration of virus can take place from the ganglia
to the Skin and Mucosa causing lesions.
Virus remains latent in ganglia, particularly of
Trigeminal (HSV type 1) & Sacral (HSV type 2) nerves.
CLINICAL FEATURES OF HSV INFECTION
⇒ The clinical features depend on the site of Infection, Age, and immune status of the host, and the antigenic type of the virus.
- Cutaneous infections : Common sites are cheeks, chin, around the mouth or on forehead or on buttock in infants as napkin rash. The typical lesion is the Fever Blisters. Eczema herpeticum is a generalized eruption caused by herpes infection in children suffering from eczema.
- Mucosal : Buccal mucosa is the commonly affected site. Gingivostomatitis, pharyngitis & herpes labialis are frequent conditions.
- Ophthalmic : Most common cause of viral associated corneal blindness. Acute Keratoconjunctivitis or Follicular conjunctivitis are the common manifestations.
- Nervous system : HSV associated encephalitis, sacral autonomic dysfunction & transverse myelitis are rare.
- Visceral : HSV may cause esophagitis, tracheobronchitis and pneumonia, is a uncommon cause of hepatitis.
- Genital : Genital herpes is the rapidly increasing venereal disease. In men, the lesions occur mainly on the penis or in urethra causing urethritis. In females, cervix, vagina, vulva & perineum are affected.
- Congenital : Transplacental infection with HSV 1 or 2 can leads to congenital malformations, but this is rare.
LABORATORY DIAGNOSIS OF HERPES SIMPLEX VIRUS
- Specimen : Specimens should be collected according to the site of lesions – Skin swab, Saliva, Vesicle fluid, Corneal scrapings, Brain biopsy or CSF.
- Direct Demonstration: The Tzanck smear is the rapid diagnostic method. Multinucleated giant cells with faceted nuclei & homogeneously stained ‘ground glass’ chromatin confirm the Herpes simplex infection.
- Isolation of the virus: Virus can be isolated on human fibroblasts, human embryonic kidney & human Amnion etc. Diagnosis can be confirmed by Immunofluorescent staining of infected cell culture.
- Serology: Virus-specific IgM antibody can be detected in serum.
- PCR: It can be used for the detection of HSV DNA in CSF.
TREATMENT OF HERPES SIMPLEX VIRUS
⇒ HSV infection can be treated with Acyclovir. It may be used in the form of ointment for the treatment of ocular lesions
⇒ Valaciclovir and Famciclovir are more effective oral agents.