Herpes Simplex Virus for PA
Herpes Simplex Virus for the Physician Assistant Licensing Exam
- Etiology:
- Caused by herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), both double-stranded DNA viruses in the Herpesviridae family.
- HSV-1: Typically associated with orolabial infections but can cause genital lesions.
- HSV-2: Primarily associated with genital herpes but may also cause oral infections.
- Epidemiology:
- HSV-1 is usually acquired in childhood through non-sexual contact, while HSV-2 is most commonly acquired during adolescence or adulthood via sexual contact.
Pathophysiology
- Latency and Reactivation:
- After initial infection, HSV establishes latency in sensory neurons (trigeminal ganglia for HSV-1, sacral ganglia for HSV-2).
- Reactivation occurs due to triggers such as stress, immunosuppression, ultraviolet (UV) exposure, or hormonal changes, resulting in recurrent infections.
- Transmission:
- Transmitted via direct contact with infected mucosal surfaces or secretions.
- Asymptomatic viral shedding contributes significantly to transmission, even in the absence of active lesions.
Clinical Manifestations
Primary HSV Infection
- Systemic Symptoms: Often more intense than recurrent infections, with fever, malaise, lymphadenopathy, and myalgias.
- Orolabial HSV-1:
- Painful vesicles or ulcers on the lips, oral mucosa, or perioral skin.
- Gingivostomatitis is common in children with primary HSV-1 infection.
- Genital HSV-2:
- Painful vesicles and ulcers on genital or perianal skin, often with dysuria and inguinal lymphadenopathy.
Recurrent HSV Infection
- Orolabial Recurrence (HSV-1):
- Manifests as cold sores, often preceded by tingling or itching.
- Genital Recurrence (HSV-2):
- Usually milder than the primary infection, with localized lesions often preceded by prodromal symptoms.
Complications
- Herpetic Whitlow:
- HSV infection of the finger, often seen in healthcare workers or patients with oral exposure.
- Herpes Simplex Keratitis:
- Corneal HSV infection, commonly HSV-1, presenting with dendritic ulcers and potential vision loss if untreated.
- HSV Encephalitis:
- Primarily HSV-1, affecting the temporal lobes and causing fever, altered mental status, focal neurological signs, and seizures.
- Neonatal Herpes:
- Acquired during delivery from mothers with active genital HSV, leading to disseminated disease, CNS infection, or localized skin/mucosal lesions in newborns.
Diagnosis
- Polymerase Chain Reaction (PCR):
- Preferred for detecting HSV in CNS infections and lesions due to high sensitivity and specificity.
- Viral Culture:
- Useful for early vesicular lesions but less sensitive than PCR.
- Serology:
- Detects HSV-1 and HSV-2 antibodies, useful for confirming prior exposure but not for acute diagnosis.
Treatment
Antiviral Therapy
- Acyclovir, Valacyclovir, and Famciclovir:
- First-line treatments that reduce symptoms and recurrence frequency.
- Primary Infection:
- Acyclovir: 400 mg PO three times daily for 7–10 days.
- Valacyclovir: 1 g PO twice daily for 7–10 days.
- Recurrent Infection:
- Acyclovir: 400 mg PO three times daily for 5 days.
- Valacyclovir: 500 mg PO twice daily for 3 days.
- Suppressive Therapy:
- For patients with frequent recurrences or those desiring to reduce transmission risk.
- Acyclovir: 400 mg PO twice daily.
- Valacyclovir: 500 mg or 1 g PO once daily.
Management of Complications
- HSV Encephalitis: Requires high-dose IV acyclovir (10 mg/kg every 8 hours) for 14–21 days.
- Neonatal Herpes: Requires immediate IV acyclovir treatment (20 mg/kg every 8 hours) for 14–21 days.
- Herpetic Keratitis: Managed with topical antivirals like trifluridine or oral antivirals, and referral to ophthalmology.
Prevention and Reduction of Transmission
- Condom Use: Reduces transmission but does not completely prevent it.
- Partner Notification: Important to inform sexual partners; suppressive therapy can help lower transmission risk.
- Cesarean Delivery: Recommended for pregnant women with active genital lesions at labor to prevent neonatal transmission.
Key Points
- HSV-1 primarily causes orolabial infections, and HSV-2 is mainly responsible for genital infections, though both can affect either site.
- Latency and Reactivation: HSV establishes latency in sensory ganglia, with reactivation triggered by stress or immunosuppression.
- Diagnosis is confirmed with PCR, especially for CNS involvement; serology helps confirm past infection.
- Treatment with acyclovir, valacyclovir, and famciclovir reduces symptoms and recurrence frequency.
- Prevention involves condom use, partner notification, and cesarean delivery in cases of active maternal infection at the time of labor to protect neonates.