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.

Local viral infections

Herpes simplex

• Herpes simplex virus type 1 (HSV-1) usually causes peri-oral 'cold sores' and herpes simplex virus type 2 (HSV-2) is usually responsible for genital herpes.
• Both types of HSV 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 1,000 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.
• HSV can also be inoculated from external sources. Examples include:
  • Nailfold infection in a healthcare 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 zoster²

• 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 midline.
• The classic rash consists of macules and papules which develop into vesicular lesions in a dermatomal distribution (most commonly on the chest).
• The rash tends to last 7-10 days. Healing can take 2-4 weeks.
• 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).³
• 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).
• Skin complications can include secondary infection, scarring and changes in pigmentation.²
• In young people, herpes zoster tends to regress without problems. However, the elderly are more likely to have complications (especially postherpetic neuralgia).⁴
• An oral antiviral (e.g. aciclovir) should be started within 72 hours for:
  • Anyone over the age of 50 years.
  • People of any age who have:
  • Ophthalmic involvement.
  • Immunocompromised.
  • Patients with a rash on the neck, limbs or perineum.
  • Moderate or severe pain.
  • Moderate or severe rash.
  If the patient meets one of these criteria, an antiviral can be started within 1 week if the 72-hour window is missed.
• The rash should be kept clean and dry to reduce the risk of secondary bacterial infection.
• The lesions of shingles shed virus. Hence, it is possible, though unlikely, for people to contract chickenpox from shingles (but impossible to 'catch' shingles from chickenpox).
• If the rash can be covered, normal activities can be followed; otherwise contact with others (e.g. at school or work) should be avoided until it is completely dry and the vesicles have crusted over.

Molluscum contagiosum⁴

• 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 1-6 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).
• Vertical transmission from mother to fetus has been reported.⁵
• 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.⁶ Otherwise, possible treatments include squeezing, piercing, 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.⁷
• Eczema can occasionally occur around the lesions; this should be treated with 1% hydrocortisone cream.
• Secondary bacterial infection should be treated with fusidic acid cream 2%.
• Referral should be considered for HIV-positive patients with extensive lesions and patients with ocular lesions. Patients with anogenital lesions should be screened for sexually transmitted diseases.

Warts⁸

• 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 most common in childhood and are spread by direct contact or auto-inoculation. It may take up to 12 months for the wart to appear.
• They are more frequent and more troublesome in association with immunosuppression.
• Warts are more infectious when they are wet or when they bleed from trauma (e.g. scratching).
• 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.⁶
• If the patient is desperate for treatment for cosmetic reasons, cryotherapy has been found to be the most effective option in primary care. Patients should be warned of pain, infection, blistering and depigmentation.
• Avoid cryotherapy in patients with:
  • Raynaud's syndrome.
  • Peripheral vascular disease.
  • Peripheral neuropathy.
  • Periungual sites - (risk of subungual haematoma and pain).
• Topical salicylic acid (which can be obtained without prescription) is another option and is more appropriate than cryotherapy for younger children. However, it needs to be used for up to 12 weeks and is associated with local skin irritation.
• Facial warts should not be treated in primary care.
• Clinical Knowledge Summaries do not recommend over-the-counter freeze sprays, glutaraldehyde, formaldehyde, and silver nitrate.

Orf⁹

• 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 10-14 days later.
• The lesion may be covered to prevent spread although human-to-human transmission is rare.
• It resolves spontaneously in 3-6 weeks.
• A vaccine has been developed to control the infection in sheep.

Viral infections that produce rashes

There are a number of viral infections that may cause a rash - most of them typically in childhood. 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 (the 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).

Other viral infections with skin involvement

Hand, foot and mouth disease¹⁰

• 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 3-5 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 veterinary 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 although epidemics of enterovirus 17 in the Asia-Pacific region have caused serious neurological disease and occasional fatalities.

Nonspecific viral rash

This is a widespread erythematous rash sometimes seen in viral infections. It is accompanied by the common symptoms of a viral infection, such as fever, headache and malaise. The rash usually develops rapidly. The appearance varies but commonly takes the form of an erythematous blotchy eruption.

Crosti-Gianotti 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 Crosti-Gianotti syndrome include:
  • Hepatitis B virus
  • Epstein Barr virus
  • Coxsackie viruses
  • Echoviruses
  • 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.¹¹
• The spots are 5-10 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.

Viral skin infections and sport

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 'scrum pox'. In a study of American college wrestlers 7.6% were reported to have had a herpes skin infection in the preceding 12 months.¹²
• 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.¹³

Common warts

Infection can occur if infected debris from warts comes in contact with abraded skin and can result in either auto-inoculation 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.

Immune compromise

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.

Document references

1. Ichihashi M, Nagai H, Matsunaga K; Sunlight is an important causative factor of recurrent herpes simplex. Cutis. 2004 Nov;74(5 Suppl):14-8. [abstract]
2. Shingles, Clinical Knowledge Summaries (2008)
3. Fleming DM, Cross KW, Cobb WA, et al; Gender difference in the incidence of shingles. Epidemiol Infect. 2004 Jan;132(1):1-5. [abstract]
4. Molluscum contagiosum, Clinical Knowledge Summaries (2008)
5. Luke JD, Silverberg NB; Vertically transmitted molluscum contagiosum infection. Pediatrics. 2010 Feb;125(2):e423-5. Epub 2010 Jan 11. [abstract]
6. Smolinski KN, Yan AC; How and when to treat molluscum contagiosum and warts in children. Pediatr Ann. 2005 Mar;34(3):211-21. [abstract]
7. van der Wouden JC, van der Sande R, van Suijlekom-Smit LW, et al; Interventions for cutaneous molluscum contagiosum. Cochrane Database Syst Rev. 2009 Oct 7;(4):CD004767. [abstract]
8. Warts and verrucae, Clinical Knowledge Summaries (June 2009)
9. Orf, Health Protection Agency, 2010
10. Hand foot and mouth disease, Clinical Knowledge Summaries (March 2010)
11. Chuh AA; Diagnostic criteria for Gianotti-Crosti syndrome: a prospective case-control study for validity assessment. Cutis. 2001 Sep;68(3):207-13. [abstract]
12. Becker TM, Kodsi R, Bailey P, et al; Grappling with herpes: herpes gladiatorum. Am J Sports Med. 1988 Nov-Dec;16(6):665-9. [abstract]
13. White WB, Grant-Kels JM; Transmission of herpes simplex virus type 1 infection in rugby players. JAMA. 1984 Jul 27;252(4):533-5. [abstract]

Internet and further reading

• Viral skin infections, DermNet New Zealand; Good narrative and pictures
• Hardin MD; University of Iowa. Viral skin disease; Gives access to many excellent pictures

Acknowledgements