Herpes simplex is a common viral infection that presents with localised blistering. It affects most people on one or more occasions during their lives.
There are two main types of herpes simplex virus (HSV), although there is considerable overlap.
- Type 1, which is mainly associated with facial infections (cold sores or fever blisters)
- Type 2, which is mainly genital (genital herpes)
Both type 1 and type 2 herpes simplex viruses reside in a latent state in the nerves which supply sensation to the skin. During an attack, the virus grows down the nerves and out into the skin or mucous membranes where it multiplies, causing the clinical lesion. After each attack it ‘dies back’ up the nerve fibre and enters the resting state again.
First or primary attacks of Type 1 infections occur mainly in infants and young children, which are usually mild or subclinical. In crowded, underdeveloped areas of the world up to 100% of children have been infected by the age of 5. In higher socioeconomic groups the incidence is lower, for example less than half of university entrants in Britain have been infected.
Type 2 infections occur mainly after puberty, often transmitted sexually. The initial infection more commonly causes symptoms.
How do you get the infection?
The infection can be passed on from someone else with an active infection and it can also be passed on from individuals without symptoms.
The virus is shed in saliva and genital secretions, during a clinical attack and for some days or weeks afterwards. The amount shed from active lesions is 100 to 1000 times greater than when it is inactive. Spread is by direct contact with infected secretions.
Minor injury helps inoculate the virus into the skin. The virus can be inoculated into any body site to cause a new infection, whether or not there has been a previous infection of either type. The source of the virus may be from elsewhere on the body especially in nail biters or thumb suckers. Herpes simplex can also be inoculated from external sources. Examples include:
- Nailfold infection in a health-care worker (‘herpetic whitlow’)
- Facial blisters in a rugby player (‘scrum pox’)
- Suckling infant with mouth sores
Following the initial infection immunity develops but does not fully protect against further attacks. However where immunity is deficient, both initial and recurrent infections tend to occur more frequently and to be more pronounced and persistent.
Primary herpes simplex
Primary infections may be mild and unnoticed, but they are often more severe than recurrences. Initial infections with Type 2 virus are generally more marked than with Type 1 virus.
Herpetic gingivostomatitis (mouth infection) is the most common clinical manifestation of primary Type 1 infection. Most cases occur in children between the 1 and 5 years of age.
After an incubation period of 4 to 5 days the symptoms begin with fever, which may be high, restlessness and excessive dribbling. Drinking and eating are painful and the breath is foul. The gums are swollen and red and bleed easily. Vesicles (little blisters) occur in white patches on the tongue, throat, palate and insides of the cheeks. The white patches are followed by ulcers with a yellowish coating. The local lymph glands are enlarged and tender.
The fever subsides after 3-5 days and recovery is usually complete within 2 weeks.
Infection with Type 2 HSV occurs after the onset of sexual activity and results in genital herpes. Penile ulceration from herpetic infection is the most frequent cause of genital ulceration seen in sexual health clinics. The ulcers are most frequent on the glans, foreskin and shaft of the penis. They are sore or painful and last for 2 to 3 weeks if untreated.
In the female, similar lesions occur on the external genitalia and the mucosae of the vulva, vagina and cervix. Pain and difficulty passing urine are common. Infection of the cervix may progress to a severe ulceration.
Recurrent herpes simplex
After the initial infection, whether 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 oral herpes.
Recurrences can be triggered by:
- Minor trauma to the affected area
- Other infections including minor upper respiratory tract infections
- Ultraviolet radiation (sun exposure)
- Hormonal factors (in women, flares are not uncommon prior to menstruation)
- Emotional stress
- Operations or procedures performed on the face
- Dental surgery
In many cases no reason for the eruption is evident.
Recurrent infections differ from first infections in the smaller size of the vesicles and their close grouping. Recurrences of Type 1 infection can occur on any site but they are most frequently on the face, particularly on the lips (‘herpes simplex labialis’). They do not usually result in blisters inside the mouth. Recurrences of Type 2 infection may also occur on any site but most often affect the genitals or buttocks. Recurrent HSV tends to always affect the same region, but not necessarily the identical site.
Itching or burning is followed an hour or two later by small, closely grouped vesicles on a red base. They normally heal in 7-10 days without scarring. Generally the affected person feels quite well but they may suffer from fever, pain and have enlarged lymph nodes nearby.
Although the vesicles usually form an irregular cluster, they may be arranged in a line rather like shingles (zosteriform distribution), particularly when affecting the lower chest or lumbar region.
White patches or scars may occur at the site of recurrent HSV attacks, which may be more obvious in those with brown skin.
Herpes in a netball player
First episode of herpes
© Dr Ph Abimelec – dermatologue
Scarring and blistering on buttock
- Eye infection
- Herpes simplex may cause swollen eyelids and conjunctivitis with opacity and superficial ulceration of the cornea (dendritic ulcer). The lymph gland in front of the ear is often enlarged and tender.
- Throat infection
- Throat infections may be very painful.
- Eczema herpeticum
- HSV in patients with atopic dermatitis or Darier disease may result in a severe rash known as eczema herpeticum. Numerous blisters and scabs erupt on the face or elsewhere, associated with swollen lymph glands and fever.
- Erythema multiforme
- Recurrent erythema multiforme is an uncommon reaction to herpes simplex. Erythema multiforme mainly appears on the hands, forearms and lower legs and is characterised by target lesions, which sometimes blister.
- Nervous system
- The nerves to the face may be infected by HSV, producing temporary paralysis of the affected muscles, sometimes with each attack. Rarely neuralgic pain may precede each recurrence of herpes by 1 or 2 days (Maurice's syndrome). Meningitis is rare.
- Widespread infection
- This is more likely to arise in debilitated patients and may be serious.
Mild uncomplicated eruptions of herpes simplex require no treatment. They may be covered if desired, e.g., with a hydrocolloid patch.
Severe infection may require treatment with an antiviral agent. Typical doses of oral antiviral drugs for cold sores are:
- aciclovir – 200mg five times daily for 5 days
- valaciclovir – 1 g three times daily for 7 days
- famciclovir – as a single dose of 3 x 500mg.
In New Zealand, valaciclovir and famciclovir are not currently funded by PHARMAC.
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 attacks but a single course cannot prevent future attacks. Repeated courses may be prescribed or the medication may be taken continuously to prevent frequent attacks.
Topical aciclovir or penciclovir, in the form of a cream applied to affected areas, shortens attacks of recurrent herpes simplex provided it is started early enough.
On DermNet NZ:
- DermNet's page on herpes simplex translated into Finnish
- Genital herpes
- Eczema herpeticum
- Viral skin infections
- Erythema multiforme
- Atopic dermatitis
- Herpes virus pathology
- Herpes simplex eye infection – BestHealth from BMJ Publishing; free access for New Zealanders subsidised by Ministry of Health
- Cold sores – BestHealth from BMJ Publishing; free access for New Zealanders subsidised by Ministry of Health
- New Zealand Herpes Foundation
- Dermatologic Manifestations of Herpes Simplex – Medicine Reference
- Viral infections of the mouth – Medscape Reference
- Cold Sores – EmedicineHealth
- Herpes Guide.ca – SkinCareGuide.com
- Herpes Simplex – British Association of Dermatologists
- Patient information: Cold sores (oral herpes) (The Basics) – UpToDate (for subscribers)