At least 85% of the world population have serological evidence of having had a herpes simplex infection. Many pass the vuris on even when they have no obvious active infection, by “asymtomatic viral shedding”. The so called “quiet pandemic” will be with us for a while.
Definition & Epidemiology
Herpes simplex infections can be primary- the first infection in a previously seronegative patient – or recurrent. The two are separated by a latent phase.
THE PHASES OF HERPES SIMPLEX INFECTION
- Follows direct contact with an infected individual, either with active disease or shedding viral particles during a latent phase.
- An acute gingival stomatitis in children is the most common type.
- Genital herpes simplex is also common.
- Other manifestations include a “herpetic whitlow” on a fingertip, and innoculation herpes elsewhere.
- Primary episodes are usually more severe than recurrences.
- Complications include eczema herpeticum, dissemination in the immunosuppressed, and encephalitis
- This is lifelong, despite treatment.
- The virus persists in sensory nerve ganglia.
- Virus particles may be shed asymptomatically.
- Virus is reactivated and travels peripherally in sensory nerve fibers.
- Trigger factors include minor trauma, febrile illnesses, ultraviolet light and possibly stress.
- Replication in the skin or mucous membrane then creates a recurrens.
- The commonest site are the face and genitals.
- Complications include: Erythema multiforme (65% of attacks are triggered by a herpes simplex recurrence within the preceding two weeks), eczema herpeticum, persistent ulceration in the immunocompromised and keratoconjuctivitis.
Infections are least common in the highest socio-economic class. By age 30, 50% of adults of high economic status in the US are seropositive to HSV-1, in contrast to 80% of those of lower status.
Two types of herpes simplex virus are recognized. HSV-1 and HSV-2. They are closely related but differ in their epidemiology, although both are spread by close personal contact.
- These are usually acquired in childhood after contact with infected saliva. Most facial lesions are caused by HSV-1.
- Features typical of recurrent HSV-1 infection are:
- A prodromal itch or tingling lasting a few hours.
- Groups of blisters that appear on an erythematous background.
- Infectivity is maximal for the first 2 days of an outbreak.
- Lesions arise in the same general area, but not in exactly the same place each time.
- Scabbing follows vesication. Healing takes 5-7 days, and usually leaves no scar or permanent loss of sensation
These are transmitted sexually, and begin to appear at puberty or are spread from a mother’s genital tract infection to a newborn child. Most genital infections are caused by HSV-2.
Some features are:
- The longer a primary infection lasts, the more frequent are the recurrences.
- The median recurrence rate is about one attack every 3 months for HSV-2 infections (and far less often for genital HSV-1 infections). Recurrence rates decrease with time.
- Recurrences are harmful physiologically
Prevention is difficult because the virus is ubiquitous and spread by people with no obvious active infection. Also, about 80% of genital herpes is transmitted when there is no sign of infection. Regular use of condoms helps prevent genital herpes and a high protection factor sunscreen helps to prevent recurrent facial lesions.
Those looking after patients with atopic eczema should stay away if they have cold sores because eczema herpeticum is so serious.
Suppressive long-term antiviral therapy may be needed for particularly frequent or severe relapses.
Mild outbreaks do not need treatment. The introduction of aciclovir (DNA polymeras inhibitor) was a milestone although it does not eradicate the virus. Topical aciclovir and penciclovir creams shorten the attack if they are used early enough.
The decision to use oral antiviral therapy for recurrent facial herpes simplex depends on the frequency and severity of relapses and the damage being done to the quality of life.
Long-term suppressive therapy can be considered in genital herpes relapsing more than 5 times per year. Vaccine therapy is still being evaluated.