Genital herpes

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

The sexual-health task is broader than naming a viral ulcer. The clinician must recognise a compatible episode, obtain a useful lesion sample, relieve pain and urinary difficulty, screen for relevant coinfection, and leave the patient with an accurate account of what the diagnosis does and does not mean.

Either HSV-1 or HSV-2 can produce anogenital infection. Typing matters for prognosis because genital HSV-2 tends to recur more often, but morphology cannot establish the type. After a mucocutaneous episode the virus remains latent in sensory ganglia and can later reactivate as lesions or asymptomatic shedding.

A first clinical episode means the first one noticed, not necessarily a recent acquisition. Previously unrecognised infection may become symptomatic long after transmission, so confident claims about when infection occurred or which partner transmitted it are medically unsound and potentially harmful.

Treatment is matched to the patient’s current problem. A first episode receives prompt systemic therapy and supportive care; a patient who recognises recurrence may keep an episodic course ready; and frequent, painful or distressing recurrences may justify daily suppression after a shared discussion. None of these approaches removes latent virus.

Counselling is part of treatment. It should cover prodrome, recurrence plans, asymptomatic shedding, condoms, sex during lesions, partner communication and pregnancy. The aim is informed risk reduction and restored sexual confidence, while recognising that a manageable infection can still cause disproportionate anxiety or relationship strain.

Key points

Think of genital HSV when pain, dysuria and tender nodes accompany grouped vesicles or shallow erosions; first episodes may also produce fever and substantial malaise.
A recurrence is usually shorter and more localised, and a patient may recognise tingling or burning before lesions return in the same region.
Take material from a fresh vesicle or ulcer base for typed HSV NAAT; an HSV blood-antibody result cannot assign the cause of today’s ulcer.
Treat a convincing first episode within five days of onset or while lesions are still appearing, without waiting for the laboratory result.
Give aciclovir 400 mg orally three times daily for five days for an uncomplicated first episode, extending when healing is incomplete.
Combine antiviral treatment with regular analgesia, saline bathing, topical lidocaine and a practical plan for painful urination.
Explain that shedding can occur without visible lesions: avoiding sex during prodrome or an outbreak and using condoms lowers risk but cannot promise zero transmission.
Do not use an outbreak to date acquisition or identify its source; ask about pregnancy and offer counselling that supports disclosure without blame.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Mucocutaneous exposure

HSV reaches genital or perianal epithelium through intimate skin or mucosal contact; penetration is not required and a transmitting partner may have no visible lesion.

Either viral type may be genital

Orogenital or genital contact can introduce HSV-1, while HSV-2 is commonly maintained through genital transmission; the type cannot be inferred from appearance.

Shedding between outbreaks

Intermittent release of virus from clinically normal skin explains transmission when neither partner has recognised a recurrence.

Exposure around birth

An infant is chiefly endangered by contact with maternal genital virus during delivery, with greatest concern when acquisition occurs late enough that maternal antibody protection is limited.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Local cytopathic infection
Replication in anogenital epithelium disrupts superficial cells, so fragile vesicles rapidly become tender erosions or ulcers before examination.
2
Lifelong sensory latency
After the mucosal episode, viral material travels in sensory nerves and persists silently within regional ganglia despite complete skin healing.
3
Return to the same territory
Reactivation sends virus back along sensory pathways, accounting for a recognisable prodrome and lesions recurring within a limited anatomical distribution.
4
Clinical expression follows host control
Effective cellular immunity limits most recurrences, whereas major immune compromise permits prolonged, atypical, extensive or treatment-resistant disease.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

First recognised genital episode

Multiple painful vesicles, superficial ulcers or tender erosions with dysuria, bilateral nodes and systemic upset form the classic presentation, although lesions may be sparse or already ulcerated when examined.

Patient-recognised recurrence

Focal tingling, burning or neuralgic discomfort followed by a small crop of lesions in a familiar anogenital distribution supports reactivation and allows very early episodic treatment.

Atypical mucosal disease

Fissures, proctitis, cervicitis or a few non-specific erosions can be HSV; sampling and the anatomical exposure history are more reliable than waiting for textbook vesicles.

Sacral radiculitisRed flag

A distended bladder, inability to pass urine, constipation, saddle sensory change or leg symptoms during an episode indicates possible sacral nerve-root dysfunction and requires urgent hospital assessment.

Organ-threatening or extensive infectionRed flag

Diffuse lesions with encephalopathy, meningism, hepatitis, pneumonitis or sepsis signals disease outside an uncomplicated genital episode and requires syndrome-specific inpatient care.

Pregnancy or neonatal presentationRed flag

Possible new maternal infection near birth, active lesions in labour, or illness in an exposed neonate requires immediate maternity or neonatal coordination because management depends on acquisition timing and the infant’s clinical state.

Red flags requiring action

A painful episode accompanied by a palpable bladder or inability to void needs urgent assessment for retention, not advice about dysuria alone.
Perineal numbness, constipation, leg symptoms, severe headache, photophobia, neck stiffness or altered behaviour raises concern for sacral or central nervous-system involvement.
Widespread vesicles, marked constitutional illness, hepatitis, respiratory compromise or shock is an emergency, particularly during pregnancy or major immunosuppression.
Vesicles, conjunctival disease, poor feeding, temperature instability, lethargy or seizures in a neonate with possible exposure requires immediate neonatal assessment and intravenous antiviral treatment.
Suspected first acquisition late in pregnancy needs same-day maternity and sexual-health input because the timing of acquisition drives neonatal risk.
An ulcer that enlarges, becomes hypertrophic or fails to heal despite adherent therapy in advanced HIV requires resampling, resistance work-up and reconsideration of the diagnosis.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Typed HSV NAAT from a lesionFirst step
Why
Demonstrate HSV in the symptomatic site and distinguish HSV-1 from HSV-2 for prognosis and counselling.
Interpretation and limitations
Unroof a fresh vesicle or sample the ulcer base; yield falls as healing progresses, so a negative late specimen does not fully exclude a clinically typical recurrence.
02
Syphilis assessment
Why
Detect an important alternative or concurrent cause of genital ulceration.
Interpretation and limitations
Use serology and direct lesion testing where available; repeat serology when a recent exposure could still be within the window period.
03
HIV and exposure-led STI testing
Why
Identify coinfection and immune compromise while addressing all sites involved in the sexual history.
Interpretation and limitations
Choose anatomical chlamydia and gonorrhoea samples and hepatitis testing from exposure, and schedule repeat HIV testing when the initial result does not close the window.
04
Pregnancy and acquisition assessment
Why
Separate established recurrent disease from possible acquisition during pregnancy and determine the gestational context.
Interpretation and limitations
A first episode near delivery has different neonatal implications from established recurrence and should trigger the joint specialist pathway.
05
Neurological and renal work-up
Why
Define suspected meningitis, encephalitis or radiculitis and make antiviral delivery safer.
Interpretation and limitations
Obtain CSF, imaging or renal tests as the syndrome requires, but do not delay emergency specialist-directed antiviral treatment for suspected organ-threatening disease.
06
Repeat viral sampling for non-healing disease
Why
Investigate antiviral resistance or an alternative diagnosis in a profoundly immunosuppressed patient.
Interpretation and limitations
Confirm adherence, resample the lesion and request specialist culture or susceptibility testing; resistance is not the default explanation in an immunocompetent person.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Early syphilis

A chancre may be less painful and more indurated, but overlap is sufficient that treponemal testing belongs in the ulcer assessment rather than being decided by appearance.

Mpox

Firm or umbilicated lesions, systemic symptoms and a compatible contact history prompt lesion-specific testing because genital mpox can initially resemble HSV.

Reactive aphthous ulceration

Large sharply bordered ulcers may follow systemic illness or accompany oral aphthae without HSV detection; recurrent multisystem disease broadens the inflammatory work-up.

Mechanical or irritant injury

Friction, shaving, topical products and dermatitis create fissures or erosions whose distribution and exposure history do not follow a neural prodrome.

Behçet disease or other inflammatory ulceration

Repeated oral and genital ulcers with ocular, skin, vascular or neurological features require multidisciplinary assessment after common infections are addressed.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01FIRSTTreat the first episode promptlyFirst stepA compatible first clinical episode began within five days, or fresh lesions are continuing to appear.

1Sample an active lesion for typed HSV NAAT and offer syphilis, HIV and site-specific STI testing without making treatment conditional on the results.
2Start aciclovir 400 mg orally three times daily for five days.
3Make pain and urination manageable with regular analgesia, saline bathing, topical lidocaine and advice such as passing urine in water.
4EscalationReview near the end of the course; extend treatment if lesions are still forming or substantial ulceration has not healed, and escalate retention or neurological symptoms immediately.

02URGENTSeparate retention from systemic HSV diseaseThe episode includes inability to void, neurological features, severe constitutional illness, dissemination, inability to take tablets or major immune compromise.

1Assess observations, bladder volume, sacral and central neurology, renal function and evidence of hepatic, respiratory or widespread involvement.
2Admit when retention, meningism or severe illness needs inpatient care; provide analgesia and urinary drainage when indicated.
3When an adult with genital herpes cannot swallow or tolerate oral therapy, give intravenous aciclovir with renal adjustment under the applicable local or specialist protocol.
4Use the matched CNS, disseminated, maternity or neonatal guidance for any organ-threatening syndrome; urinary retention alone does not define an intravenous dose or duration.

03RECURRENCEBuild a recurrence plan the patient can useA typed or well-established pattern recurs and the patient wants greater control of symptoms or uncertainty.

1Teach the individual’s prodrome and lesion pattern, while arranging review for any episode that changes character or fails to heal.
2For episodic treatment, supply aciclovir 800 mg orally three times daily for two days to begin at prodrome or lesion onset.
3For recurrences that are frequent, painful or psychologically burdensome, offer aciclovir 400 mg orally twice daily as suppression and review after six to 12 months.
4Agree how to discuss partners, condoms, sex during prodrome or lesions and pregnancy concerns, making clear that suppression reduces but does not abolish transmission.

04PREGNANCYCoordinate maternal and neonatal preventionHSV is first recognised during pregnancy, recurs near labour or could have been newly acquired late in gestation.

1Contact maternity and sexual-health specialists promptly and classify the episode as possible primary, non-primary or recurrent infection.
2Use aciclovir and any antenatal suppression at the gestation and schedule defined by the current joint pregnancy guideline.
3When a first episode occurs within six weeks of expected delivery, discuss the guideline-based birth plan because ongoing shedding risk is high.
4Document the neonatal observation, sampling and treatment plan before birth and avoid invasive fetal monitoring when active lesions make it unsafe.

Key medicines and prescribing safety4 treatments · regimens, roles and cautions

Reduces the duration and intensity of an uncomplicated first recognised episode when started while viral replication remains active.

Aciclovir for first episode

Give 400 mg orally three times daily for five days, starting within five days of onset or while new lesions continue to appear.

Review renal function when clinically relevant, maintain hydration and reassess at day five so continuing lesions or poor healing are not overlooked.

Gives a patient who recognises their recurrence pattern a short course that can be started before lesions are well established.

Aciclovir episodic recurrence

Give 800 mg orally three times daily for two days, begun during prodrome or immediately when recurrent lesions appear.

Provide advance supply only with a clear self-start plan; renal impairment needs dose review and a changed or persistent ulcer needs examination.

Reduces recurrence frequency and asymptomatic shedding while the medicine is taken and may relieve transmission anxiety.

Aciclovir suppressive therapy

Give 400 mg orally twice daily for continuous suppression, with review after six to 12 months.

Set expectations that latency and some transmission risk remain; review adherence, renal context, recurrence burden, relationships and the patient’s preference to continue.

Maintains systemic antiviral delivery when oral administration is not possible and is also used within separately defined protocols for organ-threatening HSV syndromes.

Intravenous aciclovir in a matched severe-disease protocol

There is no universal intravenous dose for urinary retention, neurological, disseminated, pregnancy-associated and neonatal presentations. For adults with genital herpes who cannot swallow or tolerate oral treatment, use intravenous aciclovir under the applicable specialist or local protocol with renal adjustment.

Treat the underlying complication as well as the virus: retention may need catheterisation, while CNS, disseminated, pregnancy-associated and neonatal disease each determines its own regimen. Hydrate and monitor renal and neurological status.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Painful urinary dysfunction

Severe vulval or penile pain can inhibit voiding, while sacral nerve involvement can impair bladder emptying; examination of bladder and neurology separates these mechanisms.

Meningeal or radicular disease

HSV, particularly HSV-2, can produce headache and meningism or inflame sacral roots, causing retention, constipation and altered perineal sensation.

Disseminated or chronic infection

Pregnancy and profound immune compromise increase the chance of visceral spread or persistent atypical ulcers requiring inpatient or specialist management.

Neonatal herpes

Infection acquired around delivery may involve skin, eyes or mouth and can progress to encephalitis or disseminated disease, so suspected exposure needs a pre-agreed neonatal pathway.

Psychosexual morbidity

Fear of rejection, blame and unpredictable shedding can cause more lasting harm than the lesions; accurate prognosis and non-stigmatising counselling are therefore clinical interventions.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

At first-episode review, record whether new lesions have stopped, ulcers are healing, pain is controlled and the patient can void normally.
Escalate a new bladder, sacral, meningeal, encephalopathic, hepatic or respiratory feature immediately, even if genital lesions appear to improve.
During episodic therapy, check that the patient can identify prodrome and knows when a changed pattern requires examination rather than another self-start course.
During suppression, review recurrence frequency, adherence, adverse effects, kidney context, sexual wellbeing and the reason the patient values continued treatment.
Ensure repeat syphilis, HIV or other STI testing occurs after the relevant window where the initial ulcer screen was early.
For pregnancy, record type, likely acquisition category, maternity advice, birth plan and neonatal plan in a form accessible to the teams providing delivery care.
Offer a direct route back for distress, disclosure questions, a new pregnancy, a non-healing lesion or any severe symptom.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

The outbreak cannot timestamp infection

Latency and previously unnoticed symptoms mean that today’s first diagnosed episode cannot reliably identify when transmission occurred.

Typing changes the conversation

A lesion result that distinguishes HSV-1 from HSV-2 improves recurrence counselling even though it does not reveal the source partner.

Sampling has a best moment

A wet vesicle or newly ulcerated base is more informative than skin that is dry, crusted and nearly re-epithelialised.

Recurrence treatment must be ready

A short episodic course works best when the patient has medicine available and starts it at prodrome or the first visible change.

Suppression can address distress

The decision is based on pain, frequency, relationships and anxiety rather than an arbitrary recurrence count alone.

Transmission advice needs proportion

Condoms, avoiding sex during symptoms and suppression reduce risk, while honest acknowledgement of asymptomatic shedding avoids false reassurance.

11Common pitfallsFrequent interpretation and management errors.

01
Using serum HSV antibodies to declare that a current genital lesion is herpes or to date its acquisition.
02
Waiting for NAAT before treating a convincing, evolving first episode.
03
Presenting the diagnosis as proof of recent transmission or partner infidelity.
04
Treating every future genital symptom as recurrence without reconsidering syphilis, mpox, trauma or inflammatory ulceration.
05
Attributing inability to void to pain alone when a distended bladder or sacral sensory change suggests neurological dysfunction.
06
Promising that condoms or daily antivirals make transmission impossible.
07
Making a late-pregnancy or neonatal plan without the current specialist guideline and responsible team.

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