Genital herpes is caused by the Herpes simplex virus (HSV). HSV can be sub-divided into type 1 or 2. Type 1 is associated with oral herpes called a cold sore but can also affect the genitals while type 2 caused genital disease and only rarely affects the mouth. HSV 1 is very common. As much as 90% of the population in developed countries is infected. HSV 2 is less common.
Transmission of Herpes
Transmission of Herpes commonly occurs by contact with infected secretions from oral, genital or anal surfaces. Asymptomatic shedding may occur however where individuals are infectious but with no visible signs of the disease and transmission can occur in monogamous relationships after several years. This can be hugely distressing. HSV lesions are usually painful, multiple ulcers filled with straw coloured fluid, called vesicles. Once infected, the person may have flu-like symptoms, vesicles in the genitals, pain passing water and swollen glands. This is termed as the primary infection and commonly occurs within 5 to 7 days after infection. This may not occur and evidence of past infection without the vesicles is shown by antibodies in the blood to Herpes Simplex Virus. Following this primary infection, the virus lives in the nerve root locally and periodically tracks up to the skin causing episodes of the blistering rash. This occurs more commonly with type 2, on average 4 times a year: once a year with type 1.
Detection of Herpes
Detection of HSV is by detection of the virus’s genetic material, DNA in a swab from the base of an ulcer. Antibody testing may be used if a patient wants to know if they have been infected or if an ulcer is consistently negative on DNA testing but it looks like HSV clinically. It can take up to 12 weeks for antibodies to HSV to become positive.
Other Genital Diseases That May be Confused With Herpes
Not all ulcers on the genitals are herpes. Other diseases that may look like herpes are:
- The ulcer of syphilis which is called a chancre and is typically painless
- Candida (‘thrush’) – typically flat and not vesicles
- Scabies – not vesicles and more itchy than painful
- Drug reaction
- Herpes zoster (shingles) – this is usually on one side of the body
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