Viral Skin Infections

There are many viral skin infections. They range from the common to the rare, from the mild to the severe and from those 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.

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)¹
  • 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).²
• 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.³ Otherwise possible treatments include curettage, cryotherapy, wart paints such as salicylic acid and podophyllin and even the immunomodulatory agent imiquimod cream.⁴ A Cochrane review did not enthusiastically endorse any form of treatment.⁵
• 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.³

Orf

• Orf is contracted from sheep and goats. It is caused by a parapox virus, which infects mainly young lambs and goats who contract the infection from one another (or possibly from persistence of the virus in the pastures).
• Human lesions are caused by direct inoculation of infected material. It may occur in farmers, butchers, vets, children who bottle feed lambs and possibly even children who play in pastures where sheep have grazed.
• The incubation period is 5 or 6 days.
• Lesions are usually solitary, but multiple lesions do occur. The lesions are small, firm, red or reddish-blue. They form a lump that enlarges to form a flat-topped, blood-tinged pustule or blister. The fully developed lesion is usually 2 or 3 cm in diameter but may be as large as 5 cm.
  Although there appears to be pus under the white skin, incising this will reveal firm, red tissue underneath. The lesion is sometimes irritable during the early stages and is often tender.
• They usually occur on the fingers, hands or forearms but may be on the face. Red lymph lines may occur on the medial side of the elbow up to the axilla.
• There may be a mild fever.
• Allergy to the virus may produce erythema nodosum 10 to 14 days later.
• The lesion may be covered to prevent spread although human to human transmission is rare.
• It resolves spontaneously in 3 to 6 weeks.

There are a number of viral infections, most of them typically in childhood that may cause a rash. Examples include:

• Measles (morbilli)
• German measles (rubella)
• Chickenpox (varicella virus)
• Fifth disease (erythema infectiosum, due to parvovirus)
• Roseola (erythema subitum, due to herpes virus 6)
• Pityriasis rosea (cause is unknown but it may be caused by herpes virus types 6 and 7)
• Echovirus and adenovirus infections often produce a rash
• Epstein Barr virus of infectious mononucleosis or glandular fever (may cause rash but if amoxicillin or ampicillin is given there is almost invariably a rash)
• Primary HIV infection (often associated with a rash)

Hand foot and mouth disease

• Hand foot and mouth disease is common, mild and brief, most often affecting young children during the summer months.
• It is caused by Coxsackie virus A16, although it can also be due to Enterovirus 71. Several members of the family or a school class may be affected.
• Incubation period is 3 to 5 days. Infection is heralded by small, flat blisters on the hands and feet accompanied by oral ulcers. These are sometimes painful, so the child eats little and frets. There may be a mild fever. Sometimes in young children there is a rash on the buttocks.
• After a few days the blisters and mouth ulcers settle leaving no scars. Second infections are rare.
• Parents may be concerned by the name, noting the serious vetinary implications of foot and mouth disease. They must be appropriately advised (it is caused by a different and completely unrelated virus).
• Recovery without complications is the norm.

Gianotti-Crosti Syndrome

• This is a response of the skin to viral infection in which there is a papular rash which lasts for several weeks.
• Other names include papulovesicular acrodermatitis of childhood, papular acrodermatitis of childhood and acrodermatitis papulosa infantum.
• Causes of the Gianotti-Crosti Syndrome include:
  • Hepatitis B virus
  • Epstein Barr virus
  • Coxsackie viruses
  • Echo viruses
  • Respiratory syncytial virus
• It affects children between 6 and 12 months. There may be clusters and a preceding upper respiratory tract infection is not uncommon.
• A profuse eruption of dull red spots develops over 3 or 4 days. They appear first on the thighs and buttocks, then on the outer aspects of the arms, and finally on the face, often in an asymmetrical pattern. Diagnostic criteria are yet to be firmly established.⁶
• The spots are 5 to 10 mm in diameter and a deep red colour. Later they often look purple, especially on the legs, due to leakage of blood from the capillaries. They may develop fluid-filled blisters.

Kaposi's sarcoma

This is thought to be a malignancy caused by a virus. It commonly occurs in association with HIV infection and this should be sought if the diagnosis is made. Kaposi's sarcoma with HIV is more aggressive. More is mentioned in the article on HIV and skin disorders.

Sport increases the risk of transmission of dermatological infections generally. A number of features may predispose to transmission:

• There may be direct skin to skin contact (as in rugby, wrestling on other contact sports).
• Profuse sweating may cause maceration of skin and provide a portal of entry.
• Sharing wet areas predisposes to transfer of infection from feet. These include showers and swimming pools. Bare but dry feet as in judo, other oriental martial arts and gymnastics are associated with a lower risk of transmission.

Herpes gladiatorum

• The name implies association with martial arts. In association with rugby it is called 'scrumpox'. In a study of American college wrestlers 7.6% were reported to have had a herpes skin infection in the preceding 12 months.⁷
• Transmission is primarily by direct skin to skin contact, and abrasions may facilitate a portal of entry. The majority of lesions occur on the head or face, followed by the trunk and extremities.
• A prodromal itching or burning sensation is followed by clustered vesicles on an erythematous base which heal with crusts over about 1 to 2 weeks. Less often headache, malaise, sore throat and fever may be reported.
• Recurrent episodes may follow the initial infection.
• Because of its unusual location, herpes gladiatorum any be confused with impetigo, varicella, staphylococcal furunculosis, or allergic or irritant contact dermatitis.
• Accurate diagnosis requires viral immunofluorescence and cultures should be obtained by gently breaking an intact vesicle and firmly rubbing the swab tip across the base of the erosion.
• Treatment of herpes gladiatorum is with oral aciclovir or similar agents and is most effective if commenced at the first symptoms of an outbreak. Topical aciclovir is probably less effective. Any secondary infection should also be treated.
• The virus can survive for hours to days outside the host if conditions are appropriate. Hence all contaminated surfaces should be cleaned with antiseptic solution. In the vesicular phase and until the crusts have separated, patients should avoid sports which could involve physical contact.
• Herpes simplex acquired in sport is often associated with constitutional symptoms. A report of several infected rugby players shows that malaise, anorexia, neurological complications and keratitis may occur.⁸

Common warts

Infection can occur if infected debris from warts comes in contact with abraded skin and can result in either autoinoculation or transmission to susceptible individuals. However, it is not generally thought to be highly contagious and the Oxford Handbook of Sports Medicine says that it should not limit participation in contact sports. Plantar warts can cause pain on running and so limit sporting activities. Warts may also be more common in callouses which develop in sport. Treatment of plantar warts is challenging and may cause as much inconvenience to the athlete as the presence of the wart itself.

Viral skin infections tend to be much more aggressive and virulent if the immune system ,especially the T-cell system, is inadequate. The classical example is in HIV and skin disease but unusual and gross viral infections of the skin may occur in any condition in which immunity is impaired.