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General Dermatology >> Viral Infections
 

Hose causing just skin infection to those with associated systemic disease.

The following is a brief account of a selection of the important viral skin infections. Many of the diseases mentioned here are covered in greater detail elsewhere and the reader is referred to appropriate links.

Local viral infections

Herpes simplex

  • HSV1 causes cold sores and HSV2 is responsible for genital herpes.

  • Both types of herpes simplex virus reside in a latent state in the sensory nerves to the skin.

  • During an attack, the virus spreads down the nerves and out into the skin or mucous membranes where it multiplies, causing the clinical lesion. After each attack it recedes up the nerve fibre and becomes dormant again.

  • During the active phase, there is considerable shedding of virus and the lesions are highly contagious.

  • Primary infections of type 1 occur mainly in infants and young children and 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 is usually sexually acquired, after puberty and is less often asymptomatic.

  • 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 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

  • Sexual contact including orogenital sex

  • Following the initial infection, immunity develops but does not fully protect against further attacks. Where immunity is deficient infections tend to occur more frequently and to be more pronounced and persistent.

  • Recurrence may be triggered by:

  • Minor trauma

  • Other infections including coryza, hence cold sores

  • Ultraviolet radiation (sun exposure)

  • Hormonal factors (premenstrual flares occur)

  • Emotional stress

  • Operations or procedures performed on the face (including dentistry)

  • Often no cause is found

  • Mild attacks subside without treatment but if treatment is required then antivirals (for example aciclovir) are effective. They need to be started early and in recurrences the patient may take them when the areas starts to tingle without waiting for a visible lesion. In mild cases topical, rather than oral medication will suffice.

Herpes zoster

  • Varicella or chickenpox is the primary infection. During this widespread infection, which usually occurs in childhood, virus is seeded to nerve cells, usually sensory cells.

  • Herpes zoster or shingles is characterised by distribution in a single dermatome. It may not affect all of the dermatome but usually it is confined to the area of one dermatome and does not therefore cross the mid line.

  • More extensive disease may occur in immune compromised patients (for example with lymphomas and HIV).

  • Herpes zoster can strike at any age (even in children). It is much more common in the elderly. There is a slight female excess (although chickenpox affects both sexes equally)

  • It may cause itching or pain but there is usually no motor involvement. The classical exception to this is Ramsey-Hunt syndrome (there is facial nerve involvement often with face drop, like a Bell's palsy but with a rash).

  • In young people herpes zoster tends to regress without problems. However the elderly are more likely to have complications (especially post-herpetic neuralgia).

  • In the elderly or immunocompromised oral antivirals (for example aciclovir) should be prescribed as early as possible in the disease.

  • The lesions of shingles shed virus. Hence it is possible, though unlikely, for patients to contract chickenpox from shingles (but impossible to 'catch' shingles from chickenpox).

Molluscum contagiosum

  • Molluscum contagiosum is common and usually affects infants and young children. Adults may be infected but this is unusual.

  • It presents as clusters of small papules, especially in the warm moist places such as the axilla, groin or behind the knees. They range in size from 1 to 6 mm and may be white, pink or brown.

  • They often have a waxy, pinkish look and are umbilicated (a central depression of the surface). As they resolve, they may become inflamed, crusted or scabby. They may number a few or several hundred on any individual.
  • The disease is harmless but it may persist for months or occasionally for a couple of years. Rarely, it may leave tiny pit-like scars (induration).

  • Molluscum contagiosum can be spread from person to person, usually children, by direct skin contact.

  • Sexual contact in adults may transmit infection. Spread may be associated with wet conditions such as communal showers (for example after sport or swimming).
  • Lesions tend to be more numerous and more persistent in children with atopic eczema. In children lesions are common on the face and trunk.

  • Infection can be very extensive in HIV infection.

  • The best management, especially for children, is to wait for spontaneous remission. Otherwise possible treatments include curettage, cryotherapy, wart paints such as salicylic acid and podophyllin and even the immunomodulatory agent imiquimod cream. A Cochrane review did not enthusiastically endorse any form of treatment.

  • Athletes are advised to resume contact sports 48 to 72 hours after the lesions have cleared.

Warts

  • Warts or verrucae are localised infections with the Human Papillomavirus (HPV). More than 80 HPV subtypes are known of which 20 can affect the genital tract.

  • The presentation and appearance varies according to the site of infection. For example plantar warts occur on pressure-bearing areas and are flattened rather than raised.

  • Warts are commonest in childhood and are spread by direct contact or autoinoculation. It may take up to 12 months for the wart to appear.

  • They are more frequent and more troublesome in association with immunosuppression.

  • In children, even without treatment, 50% of warts disappear within 6 months (90% in 2 years). They are often more persistent in adults but usually resolve eventually.

  • As with molluscum, common warts are usually best left untreated.

 
 
 
 

 
 
 
 
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