What is Herpes Simplex Virus (HSV) 1?

From the Guidelines

Herpes Simplex Virus Type 1 (HSV-1) is a common viral infection that can cause both oral and genital herpes, and its management should prioritize antiviral therapy and counseling on transmission prevention, as recommended by the 2021 Centers for Disease Control and Prevention (CDC) Sexually Transmitted Infections treatment guidelines 1.

Diagnosis and Management

For active HSV-1 outbreaks, antiviral medications like acyclovir, valacyclovir, or famciclovir are recommended, with the goal of reducing symptoms and transmission risk. The choice of medication and dosage should be based on the severity and frequency of outbreaks, as well as the patient's overall health status.

• Acyclovir (400mg three times daily for 5-10 days)
• Valacyclovir (1g twice daily for 7-10 days)
• Famciclovir (250mg three times daily for 7-10 days) are commonly prescribed for episodic treatment 1.

Suppressive Therapy

For patients with frequent recurrences (more than 6 per year), suppressive therapy with acyclovir or valacyclovir may be prescribed to reduce the frequency and severity of outbreaks.

• Acyclovir (400mg twice daily)
• Valacyclovir (500mg daily) are effective options for suppressive therapy, as they can reduce the risk of transmission and improve quality of life 1.

Prevention and Counseling

During outbreaks, patients should be counseled to keep the affected area clean and dry, avoid touching or picking at sores, wash hands frequently, and avoid sharing personal items like towels or lip balm. Additionally, patients should be educated on the risks of transmission and the importance of using condoms and practicing safe sex. HSV-1 is highly contagious, especially during active outbreaks, and spreads through direct contact with infected saliva or skin. The virus establishes lifelong latency in nerve cells, periodically reactivating due to triggers like stress, illness, sun exposure, or hormonal changes. While there's no cure for HSV-1, medications can effectively manage symptoms and reduce transmission risk, improving the patient's quality of life and preventing complications 1.

From the FDA Drug Label

Acyclovir is a synthetic purine nucleoside analogue with in vitro and in vivo inhibitory activity against herpes simplex virus types 1 (HSV-1), 2 (HSV-2), and varicella-zoster virus (VZV) The inhibitory activity of acyclovir is highly selective due to its affinity for the enzyme thymidine kinase (TK) encoded by HSV and VZV. Using plaque-reduction assays, the IC 50 against herpes simplex virus isolates ranges from 0.02 to 13.5 mcg/mL for HSV-1 and from 0.01 to 9. 9 mcg/mL for HSV-2. Valacyclovir hydrochloride is rapidly converted to acyclovir, which has demonstrated antiviral activity against HSV types 1 (HSV‑1) and 2 (HSV‑2) and VZV both in cell culture and in vivo The EC 50 values against herpes simplex virus isolates range from 0.09 to 60 microM (0.02 to 13.5 mcg/mL) for HSV‑1 and from 0.04 to 44 microM (0.01 to 9. 9 mcg/mL) for HSV‑2.

Acyclovir and valacyclovir are effective against HSV-1.

• The drugs work by inhibiting the replication of herpes viral DNA through competitive inhibition of viral DNA polymerase, incorporation into and termination of the growing viral DNA chain, and inactivation of the viral DNA polymerase 2 3.
• The IC50 values for acyclovir against HSV-1 range from 0.02 to 13.5 mcg/mL, indicating the drug's potency against the virus.
• Valacyclovir, which is converted to acyclovir in the body, also demonstrates antiviral activity against HSV-1.

From the Research

Overview of HSV-1

• Herpes simplex virus 1 (HSV-1) is one of the two types of herpes simplex virus, the other being HSV-2 4.
• HSV-1 can cause infections with clinical manifestations ranging from benign and generally self-limiting blisters or sores to severe and life-threatening infections 5.

Treatment Options for HSV-1

• Current treatments for HSV-1 include nucleoside analogs such as acyclovir, valacyclovir, and famciclovir 4, 6, 7.
• These antiviral drugs can be used to suppress genital herpes outbreaks in immunocompetent and non-pregnant patients 4.
• Valacyclovir is also approved for the treatment of herpes labialis and herpes zoster, and is more effective than acyclovir in hastening the healing of zoster-associated pain and postherpetic neuralgia (PHN) 6.
• Novel antiviral approaches, including therapeutic vaccines and small molecule inhibitors, are being developed for the treatment of genital or labial HSV infections 5.

Efficacy of Treatment Options

• Studies have shown that suppressive antiviral therapy with acyclovir, valacyclovir, or famciclovir can decrease the number of patients with at least one recurrence of genital herpes per year 4.
• However, the evidence is of low quality due to risk of bias and inconsistency, and network meta-analysis did not show superiority of one drug over another 4.
• Current intervention for HSV-1 and HSV-2 infections consists solely of antiviral chemotherapeutic agents, and numerous experimental vaccines are under consideration 8.