Herpes Simplex Virus Types 1 & 2

• Herpes Simplex 1 and 2 (HSV-1 and HSV-2) are double-stranded linear enveloped DNA viruses.
• Both viruses are associated with erythema multiforme, herpetic whitlow, herpes gladiatorum, and keratoconjunctivitis and asymptomatic shedding is common for both.
• Both viruses belong to the Herpesviridae family and the Alphaherpesvirinae subfamily.
• HSV-2 causes 80 - 90% of cases of genital herpes, with HSV-1 causing the remainder.
• HSV-1 is primarily transmitted through saliva, causing infections mainly on the face with most primary infections occurring in childhood.
• Approximately 80% of people in the U.S. are infected with HSV-1, with 40% of those experiencing recurrent cold sores (herpes labialis).
• HSV-2 generally infects the genitals and can spread to the oral cavity, primarily occurs in adults.
• The virus replicates in the skin or mucous membranes at the infection site and travels up the neuron by retrograde axonal flow, becoming latent in sensory ganglion cells.
• HSV-1 typically becomes latent in the trigeminal ganglia, while HSV-2 becomes latent in the lumbar and sacral ganglia.
• Reactivation can be triggered by sunlight, hormonal changes, trauma, stress, and fever, leading to recurrent lesions as the virus migrates down the neuron and replicates in the skin.

Clinical Symptoms of HSV-1:

• Gingivostomatitis mainly occurs in children and is characterized by fever, irritability, and vesicular lesions in the mouth.
• Gingivostomatitis primary disease is more severe and lasts longer, with lesions healing spontaneously in 2 - 3 weeks and many children being asymptomatic.
• Herpes labialis manifests as fever blisters or cold sores that are milder and recurrent, characterized by crops of vesicles, typically at the mucocutaneous junction of the lips or nose, with recurrences frequently reappearing at the same site.
• Encephalitis presents as a necrotic lesion in one temporal lobe, fever, headache, vomiting, seizures, and altered mental status, resulting from either primary infection or reoccurrence.
• Encephalitis has a high mortality rate and can cause severe neurological issues in those that survive.
• Eczema herpeticum is an infection of the skin in patients with atopic dermatitis, commonly seen in children, with vesicular lesions at the site of the atopic dermatitis.
• Disseminated infections, such as esophagitis and pneumonia, can occur in immunocompromised patients with depressed T cell function.

Clinical Symptoms of HSV-2:

• Many infections are asymptomatic.
• Genital herpes involves painful vesicular lesions on the genitals and anal area, more severe in primary infections than in recurrences.
• Primary genital infections are associated with fever and inguinal adenopathy.
• Neonatal herpes occurs via birth canal contact with vesicular lesions, ranging from asymptomatic to severe lesions and encephalitis.
• Aseptic meningitis involves infection of the brain and spinal cord.

Diagnosis:

• The virus can be isolated from lesions by growing it in cell culture, typically showing multinucleated giant cells and ground-glass chromatin as cytopathic effects.
• A rapid presumptive diagnosis can be achieved through a Tzanck smear.
• PCR can detect HSV DNA in spinal fluid for encephalitis diagnosis.
• Serological tests can diagnose primary infections.
• HSV-1 and HSV-2 can be distinguished using monoclonal antibodies in ELISA tests to detect glycoprotein G.

Treatment:

• Acyclovir is effective for treating encephalitis, systemic diseases, primary and recurrent genital herpes, and neonatal infections.
• Foscarnet is used for acyclovir-resistant HSV-1.
• Trifluridine is a topical treatment for HSV-1 eye infections.
• Oral Acyclovir is used for treating HSV infections.
• Valacyclovir and Famciclovir are used for treating genital herpes.
• HSV-1 and HSV-2 have substantial nucleotide sequence identity (50% of their genetic material is very similar).