Viral Skin Infections

Some viruses cause only superficial infection of the skin. Some usually cause superficial infection but can cause deeper infection too. Some tend to produce a systemic disease but may also be present in the skin. Some produce a systemic rather than dermal illness but they may be manifest by a rash on the skin.

Many of the diseases mentioned here are covered in rather greater detail elsewhere and the reader is referred to the links to those articles as coverage here is intentionally superficial.

Herpes simplex

There are two herpes simplex viruses called HSV1 and HSV2. By and large, HSV1 causes cold sores whilst HSV2 is responsible for genital herpes. There may be some reversal of these two types, especially when oro-genital sex is practised.

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. Hence, during the active phase, there is considerable shedding of virus and the lesions are highly infectious.

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 rather 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

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.
Recurrence may be triggered by:

• Minor trauma
• Other infections including coryza, hence cold sores
• Ultraviolet radiation from the sun¹
• Hormonal factors. Premenstrual flares are well recognised
• 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 of the group including 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 lesion to be visible. In mild cases a topical rather than oral approach to medication will suffice.

Herpes zoster

Varicella or chicken pox 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 a distribution of 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 cross the mid line. More extensive disease may occur in immune compromise such as lymphoma.

The disease can strike at any age, including children, but it is much more common in the elderly. In most age groups there is a slight female excess that does not reflect the incidence of chicken pox as this affects both sexes equally.² It may cause itching or pain but there is usually no motor involvement. The classical exception is the Ramsey-Hunt syndrome where the facial nerve is involved and face drop often occurs, like a Bell's palsy with a rash.

In young people this tends to regress with minimal problems but the elderly are more likely to have a complicated course, especially post-herpetic neuralgia. In the young no treatment may be in order but in the elderly or immunocompromised, oral antivirals of the group including aciclovir, should be prescribed as early as possible in the disease.

The lesions of shingles shed virus. Hence it is possible, but not very likely, to catch chicken pox from shingles, but contrary to much folklore, it is not possible to catch shingles from a child with chicken pox.

Molluscum contagiosum

Molluscum contagiosum is common and usually affects infants and young children but adults may be infected too, especially via communal showers associated with sport or swimming pools.

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. 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.

Molluscum contagiosum can be spread from person to person, usually children, by direct skin contact. Wet conditions, such as when children bathe or swim together predispose. Sexual contact in adults may transmit it too.

Lesions tend to be more numerous and more persistent in children with atopic eczema. It can be very extensive and gross in HIV infection.

The best management, especially for reticent young children, is to convince parents 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 was unimpressed by any form of treatment.⁵ Athletes may resume contact sports 48 to 72 hours after the lesions have cleared.

Warts

Warts or verruccae are localised infections with the Human Papillomavirus (HPV). More than 80 HPV subtypes are known of which 20 can affect the genital tract. The shape and presentation varies greatly, mostly depending upon the location.

Warts are commonest in childhood and are spread by direct contact or autoinocculation. 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 and 90% are gone in 2 years. They are more persistent in adults but they will resolve eventually. As with molluscum, wisdom would suggest a reluctance to treat children at all.³

Orf

Orf is contracted from sheep and goats. It is 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. A single or occasionally a few lesions develop. 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.

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.

After an incubation period of 3 to 5 days, there are flat small blisters on the hands and feet, and 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 are often concerned by the name, noting the serious vetinary implications of foot and mouth disease. They must be assured that it is caused by a different virus, the child will soon recover spontaneously and without complications and that unlike foot and mouth disease, it will not be necessary to have the child "put down" or the rest of the family culled.

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 sometimes used for this skin condition 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 due to 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.

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)
• The cause of pityriasis rosea is unknown but it may possibly be due to herpes virus types 6 and 7
• Echovirus and adenovirus infections often produce a rash
• There may be a rash with the Epstein Barr virus of infectious mononucleosis (glandular fever) but if amoxicillin or ampicillin is given there is almost invariably a rash.
• Primary HIV infection is often associated with a rash.

Sport increases the risk of transmission of dermatological infections and viral infections are no exception. A number of features may predispose.

• 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 the side of swimming pools. Bare but dry feet as in judo, other oriental martial arts and gymnastics are much less of a risk for 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 immuno fluorescence 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 not simply a skin disease. 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 infective and the Oxford Handbook of Sports Medicine says that it does 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.