Virus Infections

Virus Infections

Warts

Warts are the only “human tumours which are undoubtedly due to a virus and like other tumours are due to uncontrolled proliferation of a race of altered cells. It has been known for decades that warts can be transmitted by cell-free filtrates and it is now possible to view the virus particles by electron microscopy. The spread of warts in the school-age group has amounted to a plague in recent years and the incidence of lesions in the population is between 7 and 10 per cent or even higher in institutional groups. Spread of infection occurs in hand-holding school games, possible through fomites and from walking barefoot on school gymnasium floors and swimming baths.

About two-thirds of any given crop of warts will resolve in 2 years, but in the same patient new warts may appear while others are resolving, so that it is more likely that spontaneous disappearance is due to an abiotic change in the virus than due to destruction of the virus by development of antibodies. On some hosts spontaneous disappearance may therefore be expected in 2 years, but others continue to develop fresh lesions for years.

Warts are commonest on the hand and their appearance there is too well known to need description. Occasionally paronychial warts may simulate an infective paronychia, but careful observation reveals the papilliferous part of the wart.

Plane warts are commonest on Che backs of the hands and the face, appearing as flat topped, angular, smooth papules, either the colour of normal skin or light brown. Linear groups of papules are characteristic and caused by inoculation of the virus into scratches.

Plantar warts occur mainly on the weight area of the soles and may occur at the site of some minor trauma from a shoe nail. Owing to pressure they are unable to proliferate on the surface and so bury themselves into the sole, causing discomfort on walking. A plantar wart may be solitary and grow to a centimetre or more in diameter. Spread of lesions seems facilitated by hyperhidrosis and either small scattered seedlings may occur or a mosaic group of small warts may be formed.

Callosities often cause difficulty in differentiation but they are usually found on the transverse arch, nearly always symmetrically situated on both feet and associatiated with some minor foot deformity such as pes planus. On paring the surface of a callosity the keratin remains transparent and yellow, while the pared plantar wart reveals its papillae as minute bleeding points.

Treatment. As the majority of warts resolve spontaneously it is advisable in young children to play for time. Since any treatment, even a hospital out-patient appointment entails some form of suggestion, it is impossible to prove whether such white magic works, but the prescription of a simple ointment such as 10 per cent salicylic acid in soft paraffin and the suggestion that the warts will have gone in a month is successful in about 30 per cent of children, particularly if the warts are plane.

Virus InfectionsApplication of a C02 snow stick to the wart until a rim of frozen skin appears at its base will destroy those on the limbs, or a more successful method of freezing is with liquid nitrogen, a swab dipped in this and applied to the wart for 5—10 seconds producing a very effective reaction. Large warts on the fingers may need local anaesthetic infiltrated into the base and can then be scraped off with a curette, leaving a smooth bleeding base which should be cauterised with an electrocautery or silver nitrate stick.

The treatment of choice for small multiple plantar warts is soaking in 3 per cent formalin. The solution is placed undiluted into an old tin lid or saucer, the scales scraped from the surface of the wart with scissors or nail file and the area of the sole affected soaked in the solution for 20 minutes each night. In 4-6 weeks the majority of warts are extruded. If the warts are large the foot should be soaked in warm water and the wart pared down each night, then the following paint applied: lactic acid 1 part, salicylic acid 1 part, collodion 3 parts, when the paint has dried the wart is covered with adhesive plaster. If after about a week the wart becomes very sore the treatment should be stopped for a few days then recommenced. Large solitary warts which fail to respond to the paint may be spooned out with a curette under local anaesthetic.

Filiform warts of the beard are sometimes very persistent and destruction with the diathermy or electrocautery at frequent intervals is indicated.

Ano-genital warts (Venereal warts)

Moist filiform warts in the ano-genital region are usually transmitted by sexual contact. They should be painted with 25 per cent podophyllin in spirit which is allowed to dry then thoroughly washed off with soap and water after 24 hours. The warts then rapidly resolve, though in a few cases with large long standing lesions, destruction by diathermy under general anaesthesia may be necessary. Podophyllin being a cytotoxic substance should not be used during pregnancy.

Molluscum contagiosum

Molluscum contagiosum is caused by one of the largest viruses known to man. Transmission i: commonest in swimming or Turkish baths and small, discrete pearly rounded nodules with umbilicated centres are produced, most commonly grouped in one area on the trunk. On squeezing the larger nodules a white curd-like substance is expressed consisting of degenerate epidermal cells containing many inclusion bodies. The lesions can be destroyed by freezing with liquid nitrogen or by spiking the umbilicated centres with a sharpened orange stick which has been dipped in pure phenol.

Herpes simplex

Herpes simplex is one of the commonest virus diseases of the skin and man is its natural host; over 60 per cent of people are infected and remain carriers throughout life.

Primary infection with the virus usually occurs in the first 5 years of life and may pass unnoticed. However, it can give rise to an acute gingivostomatitis associated with fever and local lymphadenitis. The lesions in the mouth resemble a profuse crop of small aphthous ulcers the gums are swollen and occasionally scanty vesicles may appear, dotted over the face and neck, uniform in size and leaving necrotic crusts after rupture. The primary lesion may involve the eye producing acute follicular conjunctivitis, which is usually self-limited.

The source of this infection can be traced in some cases to adult contacts who have suffered from recurrent herpes a few days before. In the early stages of this illness herpes antibody may be absent and a rising titre as the illness progresses is helpful in the diagnosis. Culture of the virus on chick embryo chorioallantois may also provide the answer in 3 or 4 days.

This primary infection subsides in about 10 to 14 days but the virus then remains latent in the trigeminal ganglion and on reactivation spreads down one of the branches of the trigeminal nerve to cause lesions in the area of skin supplied by the branch involved. Occasionally one of the posterior root ganglia of the spinal cord may be the latent site and give rise to recurrent lesions on the trunk or a limb. Fever is the commonest stimulus but exposure to strong sunlight or emotional disturbance seems able to provoke an attack in some. A burning uncomfortable papule is succeded by a group of small vesicles of uniform size which rapidly break leaving a crusted area, which usually heals in 7 to 10 days. When the secondary lesion involves the eye it may progress from conjunctivitis to keratitis and the formation of characteristic dendritic ulcers. Genital herpes is caused by a strain of the virus (Type 2) which differs serologically from the ordinary strain (Type 1) and which is usually sexually transmitted. The lesions appear as a cluster of vesicles on the penis, ?n women there may be extensive involvement of the vulva and vagina.

Those who suffer from recurrent herpes simplex have circulating herpes antibodies which show no rise in titre as the result of an attack of herpes simplex. In some cases erythema multiforme may follow about 10 days after the onset of the herpes (q.v.).

Treatment. Idoxuridine (0-1 per cent) in water solution is useful for treatment of the eye but does not penetrate the skin. For recurrent lesions of the skin 5 per cent idoxuridine in dimethyl sulphoxide should be applied to the affected area with a brush two-hourly by day for two days. The vesicles rapidly resolve but this rarely prevents recurrence. In adults superficial x-ray therapy (to a total of 300 rads) or Grenz rays to the area of recurrences can be followed by a long remission.

Eczema herpeticatum

The herpes simplex virus may also produce a secondary infection on skin damaged by eczema and is particularly prone to do so in babies. Contact in the cases has been with an adult suffering from herpes simplex, but vaccinia virus can produce an identical clinical picture if such infants are vaccinated or in contact with a person with a vaccination lesion. In the absence of guidance from the history only virus studies will distinguish the cause. The child with eczema becomes acutely ill with a high fever, the areas of eczema become vesicular and crusted and the local lymph nodes enlarged. The smallness, umbilication and uniformity of size of the vesicles and their tendency to group distinguishes this from pyogenic secondary infection. Fresh vesicles appear for as long as 9 days and are followed by necrotic crusts which are also similar in size.

Even the adult victim may be severely ill and in young babies this infection may be grave and death can occur from dehydration, secondary bacterial infection or adrenal necrosis.

This is the reason why infants with eczema should never be vaccinated against smallpox and should be protected from contact with anyone who has just been vaccinated. Similarly, sufferers from an attack of herpes simplex should be kept away from a case of infantile eczema or from any patient suffering from large, raw, weeping areas of dermatitis. There is no reason why the baby should not be inoculated against diphtheria, tetanus, whooping cough or poliomyelitis.

In eczema vaccinatum smallpox gamma-globulin administration ameliorates the condition and reduces the mortality. It may also be used prophylactically if vaccination is essential in an eczema subject, but for purposes of entry a medical certificate of unfitness for vaccination is accepted in most countries. The thiosemicarbazones are of value in treatment and in eczema herpeticatum the use of cytarabine by intravenous injection in a single daily dose fo. 2-3 days has been advocated.

Herpes zoster

The virus causing herpes zoster is identical in size with that of chicken-pox and serological studies reveal no antigenic difference between the virus strains. It is therefore believed that zoster is due to activation of chicken-pox virus which has lain latent in the sensory ganglia since the primary infection years before. Zoster produces an earlier and greater antibody response because of the previous infection.

Chicken-pox is predominantly a disease of children between 2 and 6 years of age while herpes zoster is uncommon under the age of 15 years and more than half the cases are over 45 years old. Zoster may follow within 3 to 7 days of exposure to varicella, may follow damage to the dorsal nerve root by tuberculosis, tumour, leukaemia or arsenic or may appear for no obvious cause.

An attack is ushered in by pain over the nerve root distribution which usually lasts for about 3 days before the eruption appears; at this stage the regional lymph nodes are enlarged and tender. The rash follows a nerve distribution and may involve one or more dermatomes, appearing in a continuous line or only in patches where the cutaneous nerves branch to the skin. Initially the eruption is a raised patch of erythema, but this is soon covered with a cluster of umbilicated vesicles which rapidly becomes purulent or haemorrhagic then form necrotic crusts. Pain usually continues with the eruption though some cases are remarkably free.

On the thorax and abdomen this linear vesicular rash, stopping sharply at the midline back and front is easily diagnosed, but involvement of the trigeminal or cervical regions and the lumbosacral areas may be more puzzling.
The ophthalmic branch of the trigeminal nerve is involved in 10 to 15 per cent of all patients. Headache and tenderness of the scalp is followed by the characteristic eruption, usually in one sheet involving the forehead to the mid-line and extending back to the scalp. Involvement of the nasociliary branch of the nerve makes eye complications more likely. One third of all these patients suffer complications varying from trivial conjunctivitis to severe kerato-conjunctivitis or iridocyclitis with secondary glaucoma. The eye is photophobic and irritable, with redness at the corneal margin. Patches of opacity may occur in the corneal substance and involvement of the iris is made apparent by sluggish reaction of the pupil or distortion of its margin.

In patients chose resistance to infection is lowered, especially by reticulosis or leukaemia, the skin lesions may not remain localised but scattered discrete vesicles identical with those of chicken-pox may appear dotted over limbs and trunk. If this occurs as the presenting sign the patient should be investigated for possible underlying disease.
The skin lesions begin to resolve in about 10 days but healing may be slow in those cases where there has been severe necrosis and the resultant scarring may be especially disfiguring on the forehead.

Treatment. If zoster can be treated within a day or two of the appearance of the rash specific chemotherapy is the treatment of choice. Idoxuridine 5 per cent in dimethyl sulphoxide painted onto the affected area with a brush two-hourly by day 2 to 3 days or cytarabine for three succeeding days by single daily intravenous injection.

After the first few days the virus ceases to replicate and these drugs are useless. At that stage local antibiotic cream to prevent secondary sepsis should be applied and pain relieved with paracetamol. Pain and the discomfort of friction of clothes is diminished if the patient rests in bed.

In herpes ophthalmicus the eye should be treated with 1 per cent atropine sulphate drops twice daily and a local antibiotic eye ointment If there is danger of ulceration of the cornea, specialist advice is required.

We do not advise the use of systemic corticosteroids in the treatment of this disease as there is no evidence that they shorten the duration of the skin lesions.

Neuralgic pain occasionally persists for months or years especially in the elderly. Analgesics are valueless in some cases and in these a form of counter irritation may be of value, freezing the affected segment with ethyl chloride spray is the simplest of these methods. Such patients with post herpetic neuralgia suffer less when their minds are occupied and they should be encouraged to go about their normal daily tasks or be given some form of occupational therapy.

Orf

Orf is caused by the virus which produces contagious pustular dermatitis in sheep. Those infected are therefore usually sheep farmers, meat porters, butchers, or even occasionally housewives handling sheep’s heads.

The lesions are usually single but can be multiple and are generally on the hand. The initial lesion is a dusky red papule which enlarges to 1 to 2 cm in diameter and then resembles a large domed pustule. If the epidermis is incised the lesion is found to contain no pus but is solid with granulation tissue.

The disease is self limiting and resolves in 5 to 8 weeks. Treatment with compresses of ½ per cent silver nitrate lotion prevents secondary sepsis.

Complications of vaccination against smallpox

Mention has already been made of the development of eczema vaccinatum in atopic eczema subjects, but even the healthy occasionally suffer complications after vaccination. Generalised vaccinia is uncommon, developing in about 1:25,000; the eruption appears 9-14 days after vaccination and may crop for 2 or 3 days. The lesions may resemble variola but are usually more limited in extent. The prognosis is good and recovery usually takes place in the same time as the primary lesion but treatment with gamma globulin immediately stops further lesions. More commonly, an erythema multiforme or a morbilliform erythema develops 7-10 days after vaccination and fades rapidly. Accidental vaccina may occur in incompletely immune contacts of the vaccinated person. The lesion goes through the same stages of a red irritable papule appearing four days later, becomes vesicular in 48 hours, increases in size and infiltration until it has become a pustule by the eighth to the eleventh day and then forms a necrotic crust. When such a lesion occurs on the face the inflammatory reaction and oedema are severe and the scar remaining may require plastic repair.