The infection: What is genital herpes?

Genital herpes is a common viral infection caused by the herpes simplex virus (HSV). There are two types of the virus, types 1 and 2 (HSV-1 and HSV-2). As well as genital herpes, HSV can infect the mouth and cause cold sores. HSV-1 and HSV-2 lesions look the same and can only be distinguished by laboratory testing.

What is a virus?

Understanding viruses and how they work is the key to understanding genital herpes.

A virus is a very primitive form of life. As an intracellular parasite, a virus cannot live by itself and is entirely dependent on the cellular machinery of the cells it invades.

Viruses and bacteria are the microbial organisms that most commonly cause infection in humans, but bacteria are larger and have their own cellular machinery which enables them to live free of cells and makes them easier to isolate and eliminate.

Viral infections

The herpes virus invades the human body, often through a crack in the skin or through the lining of the mouth and genital area.

Once inside the cells, the herpes virus uses the material in the cell to reproduce itself (known as replication). In this process, the cell is destroyed. The disruption of the host cell is responsible for the characteristic signs (blisters, etc) and symptoms (tingling, pain, etc) of herpes infections and the release of thousands of copies of the virus.

Besides entering and taking over cells at the site of infection, particles of the herpes virus enter one of the many sensory nerve fibres which are found all over the body, and proceed to move upward to where the fibre begins near the spinal cord. This is a small cluster of cells known as a sensory ganglion.

In the case of facial herpes, the herpes virus settles in a large nerve centre (ganglion) at the base of the skull, known as the trigeminal ganglion.

In the case of genital herpes, the herpes virus retreats to the sacral ganglion, situated near the tail of the spinal cord.

Once the herpes virus reaches the ganglion, it lives there for the rest of our lives.

Herpes simplex isn't the only virus many of us have living with us. Anyone who has had chickenpox is host to the Varicella zoster virus, another member of the herpes virus family. This virus remains dormant for the rest of our lives; in some people, however, it can leave the nerve ganglia, travel down the nerve fibres and cause shingles. Other chronic viruses include the glandular fever virus (EBV) and cytomegalovirus (CMV), for example.

Once a virus enters our body, whatever the virus, antibodies are produced to fight it. Antibodies are the body's natural form of defence and continue to be produced long after the initial episode.

With genital herpes, antibodies help ensure that recurrences are milder than the first herpes episode. It is very common to find antibodies in people who have never apparently experienced an episode of genital herpes. Either the initial infection was so mild that the person was unaware that it was taking place, or it was totally without symptoms and therefore unrecognised.

Viral shedding

When the HSV reactivates in the ganglion and travels down the nerve fibres to the skin surface, particles of the herpes virus may be 'shed' on the surface of the skin, with or without any signs or symptoms of herpes infection present. This is called viral shedding. Viral shedding also occurs when blistering and/or sores are present.

During these times, HSV may be transmitted to sexual partners. There is no way to tell when the herpes virus is being asymptomatically shed on the skin surface and therefore no way to predict when you may be infectious and at risk of transmitting the herpes virus to a sexual partner. However, viral shedding is most prevalent just before, during and immediately after the presence of symptoms. Viral shedding may occur approximately 5% of days per year.

Viral shedding does occur in association with outbreaks of genital herpes and therefore sexual contact should be avoided during these times. Between outbreaks, viral shedding may still occur (asymptomatic viral shedding) so, as with any new relationship, it is wise to consider using condoms to reduce the chance of transmission to sexual partners.

How genital herpes is spread

You can get genital herpes by having sexual contact (vaginal, oral or anal sex) with someone who carries HSV. It used to be believed that herpes transmission (passing it on) only occurred if herpes blisters or sores were present. However, it is now known that transmission can occur when herpes blisters or sores are not present. This can occur in two situations:



1. People who have recurrent genital herpes (repeated episodes) can transmit the herpes virus between recurrences (through asymptomatic shedding). This occurs on approximately 5% of days per year. (Remember it is quite possible your partner/s may already carry one or both of the herpes simplex viruses. Once an individual has the virus they cannot be re-infected.)

2. There are many people who are exposed to and infected by the herpes virus but never develop any signs or symptoms of the herpes infection. These people carry and may 'shed' the herpes virus from time to time without showing symptoms and in doing so may transmit the herpes infection to their sexual partner/s if they have sex at that time. Up to 80% of people get HSV from partners who have no signs and symptoms of HSV and are unaware they have the herpes infection.