Genital herpes is caused by Herpes simplex virus (HSV), either HSV-1 or HSV-2. HSV initially enters through the genitals, mouth or anus through tiny abrasions. The virus then enters nerve cells where it persists but is generally kept under control by immune cells in healthy skin. However, factors such as trauma result in weakening of the skin’s protective immunity and virus can then infect cells at the skin surface (recurrent infection).


Many people have no symptoms during either initial infection or recurrences. Initial infections may cause painful ulcers, difficulty urinating, and flu-like symptoms. Typical recurrences are small localised blisters or ulcers, and may occur not only on the genitals but also on the buttocks, thighs and anus. Most recurrences cause either no symptoms or minor itch or irritation, but infectious virus is shed from the skin during such episodes.


A swab is taken from the ulcer or itchy spot and sent for virus DNA detection, which also detects whether the virus is HSV-1 or HSV-2. Blood tests for HSV give too many false positive and false negative results, so MSHC does not offer blood testing for herpes as part of screening for sexually transmitted infections in people without symptoms.


Both virus types can cause genital herpes but with different outcomes.
HSV-1 causes oral cold sores and genital infection occurs when someone with the cold sore virus (who may or may not have symptoms) performs oral sex on someone who has had no previous exposure to HSV-1. Initial genital HSV-1 infection may be quite painful, but recurrences and symptomless viral shedding occur much less frequently than with genital HSV-2 infection. People with genital HSV-1 infection are less likely to need antiviral treatment after the initial episode and to transmit the infection to sexual partners.
Genital HSV-2 infection, on the other hand, is associated with more frequent symptomatic recurrences needing antiviral treatment, viral shedding episodes and risk of transmission. Initial oral HSV-2 infections are uncommon and almost never recur in healthy people. Oral cold sores are virtually always caused by HSV-1 infection.


Antiviral medications (Valtrex®, Famvir®, Zovirax®) are very effective and very safe, even when taken for prolonged periods. Initial infections are treated for up to 10 days to reduce the severity and duration of symptoms. Recurrences can be treated with short (1-day) courses of episodic therapy, started at the very first sign of symptoms. Frequent recurrences can be suppressed by taking a continuous daily dose of as little as 1 tablet daily. Suppressive therapy also has the advantage of reducing transmission to sexual partners. People with herpes frequently switch between episodic and suppressive therapies according to their needs and circumstances.


Avoiding direct contact with the virus is the only way to prevent infection. Therefore, avoid having sex with someone who has an active genital or oral sore as there is a high risk of transmission at this time. Herpes can, however, be present on the skin without causing any symptoms and be transmitted by someone who has no sores present. Reducing your number of sexual partners and using condoms will reduce the likelihood of coming into contact with herpes.


Studies of couples where one partner has genital HSV-2 show transmission rates of between 5-20% per year, women with no exposure to HSV-1 having the highest risk (20%) and men with previous HSV-1 infection having the lowest risk (5%). Prior HSV-1 infection may give some cross-immunity to HSV-2 infection.
People who have acquired their HSV-2 infection within the previous 12-18 months are more infectious than those with more longstanding infection. Most HSV transmissions occur within the first few months of a relationship, so it is recommended that new couples consider the following measures for at least 6-12 months:

  • Using condoms consistently will reduce the risk by about 50%.
  • If the partner with herpes takes suppressive antiviral therapy, this will reduce the risk by 50%.
  • Avoidance of skin trauma will reduce the risk of viral shedding in the partner with herpes and the risk of the other partner acquiring herpes. Silicone-based lubricants are recommended.

Some people ask for a blood test to check their prior HSV exposure. We advise that the results may not be accurate enough to assess their risk and that they should, whatever the test result, practice the simple preventative measures mentioned above.


Neonatal herpes (herpes affecting the newborn) is an uncommon but serious infection.
The risk of transmission to a newborn is greatest if a woman acquires an initial herpes infection in the last 3 months of pregnancy. In such cases caesarean delivery is always recommended. A man with cold sores should not perform oral sex on his pregnant partner, unless she is known to already have HSV-1 infection. A man with genital herpes should consider using suppressive antiviral therapy, condoms and a good lubricant throughout his partner’s pregnancy if she is at risk of acquiring his infection.
A woman with recurrent genital herpes has a very low risk of transmission to her newborn. A caesarean delivery would be considered only if visible HSV ulcers are present at the time of her delivery. Pregnant women with recurrent herpes may choose to take suppressive antiviral therapy during the final few weeks of pregnancy, to prevent recurrences and therefore avoid a caesarean delivery. This has been shown to be both safe and effective.


People who have just found out that they have genital herpes have many questions. They should get as much information as they can about herpes, so they can make fully informed decisions about treatment, safe sex and managing further recurrences. Talking to a counsellor is also an option; this provides time for the individual to explore what having herpes means for them and to discuss their concerns.

This fact sheet is designed to provide you with information on Herpes (Herpes simplex virus/ HSV). It is not intended to replace the need for a consultation with your doctor. All clients are strongly advised to check with their doctor about any specific questions or concerns they may have. Every effort has been taken to ensure that the information in this pamphlet is correct at the time of printing.
Last Updated December 2017