Introduction
Prevalence
Transmission
Primary genital herpes infection
Recurrent genital herpes infection
Complications
Asymptomatic shedding of herpes virus
Herpes simplex and pregnancy
Treatment
Herpes vaccine development
Herpes simplex is one of the most frequent infections of mankind throughout the world. There are two main types of herpes simplex virus (HSV); type 1, which is mainly associated with facial infections and type 2, which is mainly genital, although there is considerable overlap.
Both type 1 and type 2 herpes simplex viruses reside in a latent state in the nerves that supply sensation to the skin. With each episode of herpes simplex, the virus grows down the nerves and out into the skin or mucous membranes where it multiplies, causing the clinical lesion. After each episode, it "dies back" up the nerve fibre and enters the resting state again.
HSV causes lifelong infection with the potential for reactivation or recurrence. Often people refer only to HSV-2 when discussing genital herpes, but both types can cause infection in the genital area. Clinically, about 60–70% of primary genital infections are due to HSV-2 with the rest due to HSV-1.
Studies have found that up to 1 in 5 adults have evidence of HSV-2 infection. Most of these people have either no or only very mild symptoms, such that they are unaware of having been infected.
Direct skin-to-skin contact spreads HSV infection most easily. Thus, sexual contact, including oro-genital contact, is the most common way to transmit genital HSV infection. The virus can be shed in saliva and genital secretions from individuals, even if they have no symptoms, especially in the days and weeks following a clinical episode. The amount shed during active lesions is 100 to 1000 times greater. Minor injury helps spread the virus, especially into the skin. Vertical (mother to baby) transmission or auto (self) inoculation may also occur. Because HSV dies quickly with drying at room temperature, spread from objects like bath towels (fomites) is unusual.
Primary or first genital HSV infections may be mild and unnoticed, but should lesions develop, the severity is generally greater than in recurrences.
Some people also have flu-like symptoms with fever, headache and muscular aches and pains. Symptoms tend to be more severe in women than in men.
Following the initial infection, immunity develops but does not fully protect against further episodes (recurrence). Where immunity is deficient, for example, in those living with HIV/AIDS, both initial and recurrent infections tend to occur more frequently and to be more pronounced.
After the initial infection, obvious or inapparent, there may be no further clinical manifestations throughout life. Recurrences are more frequent with type 2 genital herpes than with type 1.
Recurrences can be triggered by:
In most cases, however, no reason for the recurrence is evident.
Recurrent infections differ from first infections in that the blisters are usually smaller in size and more closely grouped. They also tend to be of shorter duration than the initial infection, usually 5–10 days. Generally, the affected person feels quite well.
Itching or burning can precede by an hour or two the development of small, closely grouped blisters on a red base. These then produce shallow ulcers, on the glans or shaft of the penis in men and on the labia, vagina or cervix in women. Recurrences can cause distressingly painful symptoms, or the lesions can be unnoticed. Lesions normally heal in 7–10 days without scarring. Recurrences tend to be in the same region, but not always at the identical site.
Complications may include:
Intermittent shedding of HSV from genital skin may occur without symptoms or with unrecognised minor symptoms. The frequency of asymptomatic shedding is more common in those with type 2 genital herpes and in those who have been infected recently. Shedding is most likely to occur in the week before or after a recurrence.
The amount shed from active lesions (ie, when a person has symptoms) is much greater than between episodes. This is when the infection is most likely to be passed on, and sexual contact should, therefore, be avoided. One study of couples who avoided sexual contact during recurrences found that, over 12 months, only 1 out of 10 passed the virus on to their partner. In that study, condoms were not used. Using condoms may reduce the risk of infection even further.
In women who already have genital herpes before becoming pregnant, most can experience a safe pregnancy and vaginal delivery. There is only a minimal risk of the baby being affected. It is important that the diagnosis is discussed with the lead maternity carer so that consideration can be given to Caesarean section if there are lesions present during labour.
The highest risk to the baby is when the first episode of genital herpes occurs in the first few weeks of the pregnancy or in the last few weeks before delivery. These situations should be discussed with a specialist. Genital herpes does not affect fertility.
If you have herpes simplex, ask your doctor's advice. Antiviral drugs are indicated for primary herpes simplex infection, as symptoms may last for three weeks if no treatment is given. Patients with significant recurrences may require repeated courses or continuous prophylactic therapy for two months or more. Mild, uncomplicated recurrences of herpes simplex usually require no treatment.
Available antiviral drugs include:
In New Zealand, aciclovir and valaciclovir are currently subsidised by PHARMAC (June 2016). These antiviral drugs will stop the herpes simplex virus multiplying once it reaches the skin or mucous membranes but cannot eradicate the virus from its resting stage within the nerve cells. They can, therefore, shorten and prevent episodes while the drug is being taken, but a single course cannot prevent future episodes.
Different formulations of topical antiviral creams are available. They are not generally recommended for genital herpes and are not subsidised for this use in New Zealand.
Other treatments being studied include:
Both appear less beneficial than conventional antiviral drugs.
Vaccine development is an area of active research, and several different approaches are being tested in animal models, including therapeutic vaccines that might help those already infected. In May 2015, a promising vaccine design was announced. [1]
