Viral infections Medical Assignment Help

Herpes simplex

There are two types  of herpes simplex virus (HSV) infection-HSV types I and II.

CLINICAL FEATURES

Primary herpes gingivostomatitis (HSV-1) may be asymptomatic in children, but others can experience severe stomatitis associated with buccal ulceration, marked local lymph node enlargement and systemic features. Trauma to the skin may introduce the virus, as in glad iatoral or ‘scrumpox’. Damage to the skin over a finger may produce a herpetic whitlow especially in nursing personnel.

Type 2 genital infection may not cause symptoms in females if it is intravaginal. Vulvovaginitis causes burning irritation, dysuria and lymph node enlargement. Extragenital infection on the thigh or buttock can cause myalgia, and dysaesthesiae of the affected overlying skin. Recurrent disease may induce systemic upset with fever, headaches and meningeal irritation associated with the spread of the virus into the eNS. There is local dysaesthesiae followed by vesiculation, weeping and crusting; less commonly local erythema and papule formation occur but no blistering. Depending on the degree of secondary bacterial infection, attacks clear in 10-14 days, with separation of the crust.

COMPLICATIONS 

Ocular complications 

More serious and chronic disease can occur when the eye is the site of primary herpes infection or of recurrent attacks. Ulceration may give rise to marked local pain and oedema and produce keratitis, scarring and visual impairment.

Cutaneous complications

Recurrent HSV-1 infection is probably the most common cause of erythema multiforme, which occurs 10-14 days following vesiculation over the lips, face or mucous membranes.

Typical target or iris lesions appear usually over acral skin on the fingers, toes, palms or soles.

Eczema herpeticum

Atopic individuals can develop widespread disseminated viral infection at any time. This does not only occur when their eczema is in an active phase, nor does it occur on every occasion of contact. Nurses and parents with active cold sores should avoid nursing children with atopic eczema.

DIAGNOSIS

This is usually clinical. Rarely the virus may need to be cultured from the vesicles and differentiated immunologically from varicella zoster virus.

TREATMENT AND MANAGEMENT

Local drying agents such as ether or surgical spirit will promote crusting and diminish pain and discomfort. Povidone-iodine has a mild antiviral action and is available in an alcoholic solution or paint form (10% w/v). The astringent effect is a useful adjunct to treatment and secondary infection may not occur so readily following its use.

Specific measures include the use of idoxuridine or acyclovir. Infection of the eye is improved by the use of local application of eyedrops containing 0.1% idoxuridine or an ointment containing 0.5% idoxuridine. Idoxuridine 5-20% is applied to the skin in a vehicle such as dimethyl sulphoxide (DMSO), which aids the absorption of the active ingredient into the skin. The local applications need to be made at the onset of discomfort and for the ensuing few days.

Acyclovir, a thymidine analogue, is activated in the presence of HSV thymidine kinase. Toxicity to normal tissues is therefore reduced and treatment with this agent in severe local infection or disseminated disease in neonates, atopic individuals or those with immune deficiency may greatly reduce morbidity and mortality. The compound is available for local use as a 5% cream. In tablet form, acyclovir 200 mg five times daily for 5 days is a normal dosage for type 1 infection. This may need to be
increased or doubled when treating type 2 disease. Parenteral forms of the drug are also available for severely ill patients and for disseminated disease.

Women with genital herpes should undergo cervical screening as there may be a link with carcinoma of the cervix. This should always be performed if their sexual partners have recurrent disease.

Varicella (chickenpox)

This is a common infectious disease of childhood occurring in the winter and spring and caused by the varicella zoster virus (VZV).

Herpes zoster (shingles)

This infection usually represents the re-emergence of VZV from posterior nerve roots in the spinal cord or cranial nerves into the skin .

AETIOLOGY

This disease affects patients in their middle years or old age. Factors that cause the re-emergence of the virus are often unknown and probably represent changes in the immune state of the host. The induction of an attack by local spinal disease or an occult concomitant malignancy is unusual.

CLINICAL FEATURES

The prodromal symptoms of pain, tingling and dysaesthesia may precede by days the re-emergence of the virus into the skin. It then produces characteristic vesicles, papules or bullous lesions throughout the dermatome.

Unusual sites of involvement such as sacral nerve disease may give rise to visceral changes and lead to, for example, bladder dysfunction

COMPLICATIONS

Secondary infection increases discomfort, and in an elderly person intractable post-herpetic neuralgia may follow an attack of shingles. Trophic ulcers are sometimes seen over the face in association with cranial nerve involvement. Trigeminal nerve disease (ophthalmic division) can lead to infection of the eye. Signs that include swelling of the eyelid, conjunctivitis or blistering at the side of the nose require an ophthalmic opinion.

TREATMENT

DRYING SOLUTIONS such as calamine cream or lotion are soothing.

ANTISEPTIC POWDERS containing povidone-iodine or hexachlorophane may help to limit secondary
infection.
IDOXURIDINE 20-40% in DMSO may be applied where practical to the affected dermatome on dressings that are kept moist with the compound for the first 3-4 days of infection. This treatment should be limited to immunocompromised or elderly patients with severe disease.

ACYCLOVIR 800 mg orally five times daily for 7 days is recommended for all patients with shingles. Famciclovir is also effective and given three times a day. Acyclovir cream 5% may be applied for less severe attacks.
PREDNISOLONE in doses of 40-60 mg decreasing over 3 weeks can prevent post-herpetic neuralgia in those over 60 years of age. Dissemination of disease is not seen with systemic steroids.
MANAGEMENT OF POST-HERPETIC NEURALGIA is discussed on p. 928.

Orf

 This disease is due to a poxvirus infection that commonly affects young sheep, producing a pustular dermatitis. Vesiculopustular lesions appear around the mouth or feet of lambs, and persons coming into contact with the fluid from these may develop papular lesions on traumatized skin. Veterinary surgeons, farmers or their families and butchers are among those principally at risk.

Milker’s nodes are produced by a poxvirus that is morphologically identical to that of orf. Lesions are seen in farm workers handling the mouths or teats of cattle, and the organism may be carried by domestic cats.

CLINICAL FEATURES

Hands are usually affected. The lesions consist of redlblue papules, 1-2 em in diameter, with a grey edge and surrounding erythema. Misguided incision of such a swelling may release antigen and produce erythema multiforme. Lesions settle in 6-8 weeks and immunity appears to be lifelong.

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