• Ideally, the diagnosis of genital herpes should be carried out by a specialist in genito-urinary medicine (GUM). Confirmation of genital herpes requires identification of the herpes simplex virus (usually through viral culture), as a diagnosis based on clinical findings alone is not conclusive. GUM will carry out diagnosis, treatment, screening for other sexually transmitted infections (STIs), counselling, and follow up.
• A history and examination is necessary in primary care (even if the person is being referred) to determine the likelihood of genital herpes and exclude other causes of genital ulceration (see Differential diagnosis for more information).
• Ask about symptoms including painful ulcers, dysuria, vaginal or urethral discharge, malaise, and fever; their onset and duration, and whether similar symptoms have been experienced previously. Ask about previous STIs, recent sexual contact and relationship status, number of partners, and whether the person has a history of cold sores.
• Examine the person's external genitalia and surrounding skin (lesions are usually bilateral with signs of redness, blistering, and ulceration). Lesions can also affect the vagina and cervix in women, and men who have sex with men may present with herpes proctitis. There may also be tender bilateral inguinal lymphadenitis. Atypical herpes lesions can look different from typical genital blisters and ulceration, with an appearance of fissures, patchy erythema, linear lesions or excoriations.
• In people unable to attend GUM, take a swab from the base of a lesion for viral culture or polymerase chain reaction (PCR); seek advice if there is doubt about diagnostic sampling and transport.

• Viral culture for the detection of the herpes simplex virus (HSV) is the most widely used method for the diagnosis of genital herpes in the UK. HSV detection by polymerase chain reaction (PCR) increases detection rates by 11–71% compared with viral culture, but may not be widely available in the UK [BASHH, 2007].

CKS identified no national guidelines for assessing genital herpes in primary care. These recommendations are based on expert opinion [Sen and Barton, 2007], pragmatism, and good clinical practice.

• Diagnosis in GUM
• The clinical diagnosis of genital herpes may not be easy or reliable in primary care, as symptoms and signs vary in frequency and severity between different people, and can mimic other medical conditions [Gupta et al, 2007].
• Taking a history
• Several prevalence studies (mainly from the US) have shown a higher number of sexual partners, young age of first sexual intercourse, and a history of other sexually transmitted infections to be positively associated with herpes simplex virus (HSV) type 2 infection [Wald, 2004].
• Carrying out an examination
• If it is necessary to diagnose genital herpes in primary care, a viral culture or polymerase chain reaction for HSV is essential. It is estimated that even an experienced clinician will fail to identify 30–70% of cases of genital herpes based on history alone [Wald, 2004]. Viral culture has a specificity of virtually 100%, but the quality of specimens, storage of samples, and mode and length of transport influence sensitivity [BASHH, 2007].

• A number of different conditions can resemble genital herpes:
• Vulvovaginal candidiasis — it is estimated that over 50% of women infected with herpes simplex virus are misdiagnosed as having candidiasis or another cause of vulvitis.
• Other infections (e.g. gonorrhoea, non-gonococcal urethritis, syphilis, bacterial vaginosis).
• Skin disorders (e.g. atopic or contact dermatitis, psoriasis, scabies, folliculitis, lichen sclerosis).
• Other systemic conditions (e.g. Reiter's syndrome, Behçet's syndrome, Crohn's disease, and malignancy).

• The information regarding genital herpes being mistaken for vulvovaginal candida comes from a review article [Mark et al, 2003] and Primary Care Toolkit from the International Herpes Management Forum [Patrick, 2004]. The information regarding other infections, skin disorders, and other systemic conditions resembling genital herpes comes from review articles [Mark et al, 2003; Kimberlin and Rouse, 2004].