Genital Herpes
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Direct answer
Genital herpes is a recurrent viral infection of the anogenital region, most often caused by herpes simplex virus type 2 (HSV-2), which persists in sensory ganglia after the first episode. It presents as grouped, painful vesicles that ulcerate, and the primary episode is more severe than later recurrences. Diagnosis rests on PCR of a fresh lesion swab, and treatment combines oral aciclovir or valaciclovir with daily suppression for frequent recurrences.
What you must remember
- Commonest type: HSV-2 causes most recurrent genital herpes, while HSV-1 now accounts for a growing share of first genital episodes, often acquired through oral-genital contact.
- Primary episode: fever, malaise and tender inguinal lymphadenopathy with multiple painful vesicles that progress to shallow ulcers over one to three weeks.
- Recurrent episode: a prodrome of tingling or burning precedes fewer, smaller and less painful lesions that heal within about a week.
- Gold-standard test: HSV PCR on a swab from a fresh vesicle or ulcer is the most sensitive test and identifies the viral type.
- Tzanck smear: shows multinucleated giant cells but is insensitive and cannot distinguish HSV-1 from HSV-2.
- Episodic treatment: aciclovir or valaciclovir started early in the prodrome shortens the episode.
- Suppressive therapy: daily valaciclovir is used for patients with six or more recurrences a year, reducing both recurrence and transmission.
Primary versus recurrent episodes
A genital herpes episode is classified by whether it is the first infection with that virus type or a reactivation, and the two differ in severity and duration. The table sets out the contrast examiners expect.
| Feature | Primary episode | Recurrent episode |
|---|---|---|
| Systemic symptoms | Fever, malaise and tender inguinal nodes | Absent or mild |
| Lesions | Multiple painful vesicles that ulcerate | Fewer, smaller and less painful |
| Prodrome | Often absent | Tingling or burning before lesions appear |
| Duration | Two to three weeks or longer | Usually around one week |
| Viral shedding | Longer and heavier | Shorter and lighter |
| Antiviral course | Full course, usually seven to ten days | Short course started at the prodrome |
The primary episode carries the greatest viral load and the heaviest systemic burden, so it warrants a full treatment course. Recurrences are milder because the host has partial immunity, and a patient who recognises the prodrome can start episodic therapy before the lesions erupt. Counselling should explain that the virus persists between episodes and that shedding can occur without visible lesions, which is why condoms and suppression matter for partners.
Where the exam plants its traps
Stems on genital herpes test the viral cause, the right test and the logic of suppression.
- Trap: treating a painful genital vesicle with a single-dose antibiotic Correct: herpes is a viral infection, so an antiviral such as aciclovir or valaciclovir is required.
- Trap: using the Tzanck smear to confirm HSV type or to document cure Correct: the test is non-specific and insensitive, so PCR of a fresh lesion is used to confirm the diagnosis and type.
- Trap: assuming that genital HSV-1 is always a recurrence Correct: HSV-1 is increasingly the cause of first genital episodes, so type-specific testing guides counselling.
Frequently asked questions
Which HSV type most commonly causes recurrent genital herpes?
HSV-2 is the commonest cause of recurrent genital herpes, and it is acquired through sexual contact. HSV-1 now causes a larger share of first genital episodes, usually through oral-genital transmission, which is why type-specific testing matters for counselling.
What is the most sensitive test for genital herpes?
Polymerase chain reaction on a swab from a fresh vesicle or ulcer is the most sensitive test for genital herpes and also identifies the HSV type. The Tzanck smear is quick but insensitive and cannot tell HSV-1 from HSV-2.
When is suppressive antiviral therapy used for genital herpes?
Daily suppressive antiviral therapy is used in patients with six or more recurrences a year, and it reduces both symptomatic episodes and transmission to partners. It may also be offered to selected pregnant women late in pregnancy to lower the risk at delivery.
How does a primary genital herpes episode differ from a recurrent one?
A primary genital herpes episode is usually more severe, with systemic symptoms, multiple painful lesions and longer viral shedding. A recurrent episode is milder and shorter, and it is often preceded by a tingling or burning prodrome.
How is an acute genital herpes episode treated?
An oral antiviral such as aciclovir or valaciclovir is used to treat an acute genital herpes episode, and it works best when started early in the prodrome. Treatment does not eradicate the virus, which persists in sensory ganglia, so suppression is used for frequent recurrences.