Herpes simplex virus (HSV) occurs as two genomic subtypes. HSV type 1 is spread by direct contact and droplet infection. Most people are affected in early childhood but the infection is usually subclinical. Occasionally it can cause a self-limiting pyrexial primary illness with either clusters of painful blisters on the face or a painful gingivostomatitis. Once infected, cell-mediated immunity develops. In some individuals this response is poor and they may get recurrent attacks of HSV, often manifest as cold sores. Immunosuppression can also cause a recrudescence of HSV. HSV can also autoinnoculate into sites of trauma and present as painful blisters/pustules. For example they may be seen on the fingers of healthcare workers (’herpetic whitlow’).
HSV type 2 infections occur mainly after puberty and usually affect the genital area. Infections are often symptomatic and transmitted sexually. However, HSV type 1 can also be found in the genital area due to orogenital contact.

Other rare complications of HSV infection include corneal ulceration, eczema herpeticum (p. 1327), chronic perianal ulceration in AIDS patients and erythema multiforme.

Treatment

Oral valaciclovir (500 mg twice daily for 5 days) is used for primary HSV and painful genital HSV. Recurrent cold sores are treated with aciclovir cream but this must be used early to be effective in shortening an attack. Attacks of genital herpes become less frequent with time. Intravenous aciclovir must be used in immunosuppressed patients.

Adenoviral conjunctivitis

This is highly contagious and can cause epidemics in communities. Transmission is through direct or indirect contact with infected individuals. The onset of symptoms may be preceded by a cold or flu-like symptoms. The eye becomes inflamed and this is commonly associated with chemosis, lid oedema and a palpable preauricular lymph node. Some patients may develop a membrane on the tarsal conjunctiva and haemorrhage on the bulbar conjunctiva. Viral conjunctivitis can cause deterioration in visual acuity owing to corneal involvement (focal areas of inflammation). In 50% of the patients the conjunctivitis is unilateral.

Treatment

The condition is largely self-limiting in the majority of cases. Lubricants together with a cold compress can be soothing for patients. Strict hygiene and keeping towels separate from the rest of the household goes a long way in reducing the spread of the infection. Clinicians also need to ensure good hygiene practice to reduce cross-infection and infecting themselves. In patients with corneal involvement or intense conjunctival inflammation, topical steroids are indicated.

Herpes simplex conjunctivitis

Primary ocular herpes simplex conjunctivitis is typically unilateral. It usually causes a palpable preauricular lymph node and cutaneous vesicles develop on the eyelids and the skin around the eyes in the majority of patients. Over 50% of these patients may develop a dendritic corneal ulcer. The organism responsible for this condition is the herpes simplex virus (HSV), which is usually HSV-1 but HSV-2 can give rise to ocular infection.

Treatment

Primary ocular HSV infection is a self-limiting condition but most clinicians choose to treat it with topical aciclovir in order to limit the risk of corneal epithelial involvement.

Molluscum contagiosum conjunctivitis

This is typically unilateral and produces a red eye that generally goes unrecognized and comes to the forefront because patients fail to improve and the cornea starts to become involved. A closer look at the eyelids and the margin will reveal pearly umbilicated nodules and these are filled with the DNA poxvirus. A high index of suspicion is needed to make an early diagnosis.

Treatment

This includes curetting the central portion of the lesion, freezing the centre or completely excising the lesion. If the corneal involvement is severe or the eye is very inflamed, a short course of topical steroids such as prednisolone 0.5% or dexamethasone 0.1% is helpful.

Varicella zoster virus (VZV) causes the common childhood infection called chickenpox. It also causes herpes zoster.

Herpes zoster (shingles)

‘Shingles’ results from a reactivation of the VZV. It may be preceded by a prodromal phase of tingling or pain, which is then followed by a painful and tender blistering eruption in a dermatomal distribution. The blisters occur in crops, may become pustular and then crust over. The rash lasts 2-4 weeks and is usually more severe in the elderly. Occasionally more than one dermatome is involved.
Complications of shingles include severe, persistent pain (post-herpetic neuralgia), ocular disease (if ophthalmic nerve involved) and rarely motor neuropathy.

Treatment

Herpes zoster requires adequate analgesia and antibiotics (if secondary bacterial infection is present). Valaciclovir 1 g or famciclovir 500 mg three times daily for 7 days is used, or oral aciclovir 800 mg, five times daily for 7 days helps shorten the attack if given early in the illness. High-dose intravenous aciclovir is needed for immunosuppressed patients. It remains unclear how useful aciclovir therapy is in preventing prolonged post-herpetic neuralgia.