Herpes simplex virus is a part of the herpesviridae family (along with varicella zoster, CMV, EBV). There are 2 types:
- Herpes simplex virus 1 - causes oral (more than HSV-2), ocular and genital herpes (most common cause of genital herpes).
- Herpes simplex virus 2 - causes oral, ocular and genital herpes (more likely to cause recurrent genital herpes).
🏘️ Epidemiology
HSV infections make up 7% of all STIs. 42% of those affected are within the ages 15-24 years old.
An estimated 500 million people worldwide have HSV infection of the genitalia, while several billion have oral HSV-1.
Pathophysiology
HSV is responsible for herpes labialis (cold sores) as well as genital herpes. Many people are infected and never experience symptoms. After infection, the virus replicates in the epidermis then it travels retrograde down axons of autonomic or sensory ganglia where the virus lays dormant in the ganglia. For cold sores this is the trigeminal nerve ganglion while for genital herpes it is sacral nerve ganglia.
In this dormant state it evades the immune system → lifelong infection. The virus can periodically reactivate as it travels anterograde down the axons to the mucosal or cutaneous surface where it then produces symptoms that can vary from neuropathic tingling to recurrent ulcers. Most of the time it is asymptomatic, as we said, and the timing of the infection can never be determined.
We will discuss, oral and genital herpes (for information on ocular herpes, look here) as well as herpes simplex encephalitis.
Genital herpes is most commonly caused by HSV-1 but HSV-2 is more likely to cause recurrent genital herpes.
It is usually acquired by direct sexual contact.
Primary infection refers to the first time the virus is contracted, without pre-existing antibodies. However, it is tough to pinpoint this time as most people are asymptomatic. Recurrent infection refers to reactivation of the virus throughout its latent period.
⚠️ Risk factors
- 15-24 years old
- Female sex - twice the prevalence compared to males.
- History of STIs
- Multiple sexual partners
- MSM patients
- HIV or Immunocompromise
There are some risk factors for reactivation of latent HSV as well:
- Local trauma
- UV light
- Stress
😷 Presentation
- Ulcers or blisters of the anogenital area
- Neuropathic prodrome - usually in the genital area, lower back, buttocks or upper thighs up to 48 hours before lesions appear.
- Dysuria
- Vaginal/urethral discharge
- Headache, malaise and fever - more common in first episode/acute infection.
🔍 Investigations
⭐️ It is important to taker a good clinical and sexual history. Diagnosis can be made clinically with history and examination but ideally should be made by a specialist sexual health service.
🏆 PCR can be used if the patient is unable or unwilling to attend specialist sexual health services.
🧰 Management
Patients should be referred to sexual health services.
Antiviral treatment should be oral. Topical antivirals are not to be prescribed. It is also important to advise the patient on transmission.
Self-care measures can be used such as saline bathing, analgesia, topical anaesthetics (lidocaine gel).
First episode
Antivirals should be started within 5 days of the infection forming and continued for 5 days.
- 🥇 Aciclovir - 400mg 3x daily. This is first-line.
- 🥇 Valaciclovir - 500mg 2x daily. This is an alternative first-line
- 🥈 Aciclovir - 200mg 5x daily. Second-line.
- 🥈 Famciclovir - 250mg 3x daily. Also second-line.
Recurrent episodes <6 per year
A short-course treatment can be given.
- Aciclovir - 800mg 3x daily for 2 days.
Recurrent episodes >6 per year
A suppressive approach to treatment can be applied.
- Aciclovir - 400mg 2x daily for a maximum of one year before reviewing.
Oral herpes also known as herpes labialis or simply cold sores are mild, self-limiting infections of the lips, cheeks, nose, gums.
It is mainly caused by HSV-1 and rarely with HSV-2 (associated with oral sex).
😷 Presentation
- Oral ulcers
- Prodrome of pain, burning, tingling, itching and paraesthesia
- Sore throat/mouth and prodrome of fever - in gingivostomatitis.
🔍 Investigations
It is purely clinical diagnosis.
These may suggest more serious disease such as oral cancer:
- Unexplained ulceration lasting more than 3 weeks
- Red or white patch in the oral cavity consistent with erythroplakia or erythroleukoplakia
These patients need to be referred for appointment within 2 weeks.
🧰 Management
- 🥇 It is self-resolving and usually can be managed with paracetamol or ibuprofen.
- Topical anaesthetics and topical antivirals may be found useful by some but shouldn’t be prescribed (they are available over-the-counter if the patient wishes).
- Oral antivirals (aciclovir or valaciclovir) may be prescribed if the patient is Immunocompromised or if there is recurrent oral herpes infection.
Herpetic whitlow is another HSV infection that arises on the distal phalanx of the fingers. They usually are due to HSV-1.
😷 It causes tenderness, oedema, vesicles (which may become purulent and form ulcers) and they may have systemic symptoms such as fever and malaise.
🔍 It is diagnosed clinically.
🧰 Aciclovir within 48 hours of onset.
Herpes simplex encephalitis is an infectious encephalitis that commonly affects the temporal lobes as well as the inferior frontal lobes. HSV-1 is responsible for 95% of cases
😷 Presentation
- Fever
- Headaches
- Psychiatric symptoms
- Seizures
- Vomiting
- Aphasia and other focal features. Temporal lobe is associated with Wernicke’s aphasia which is a fluent aphasia where the patient is able to speak but speak nonsensical sentences. Wernicke’s area is responsible for language comprehension.
🔍 Investigations
- Lumbar puncture - CSF is checked for elevated proteins and lymphocytosis.
- PCR - to confirm HSV infection.
- EEG - lateralised periodic discharges at 2Hz.
- CT - shows medial temporal and inferior frontal changes but is normal in 1/3rd of patients.
- MRI is a better Imaging technique.
🧰 Management
- IV aciclovir
If treatment is started promptly, the mortality is 10-20% but if untreated it is close to 80%