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HSV-1 Infections

HSV-1 primary infection

The mouth.

Most primary infections with HSV-1 are asymptomatic. However, primary infection can cause a variety of clinical symptoms such as infection of the mouth and gums (gingivostomatitis) and a sore throat (pharyngitis) in children. Lesions may occur anywhere in the oral region and may involve the roof and floor of the mouth, as well as the inside of the cheek (the buccal mucosa). Disease may develop over a few days and can be painful.

The child will often be cranky and irritable, be unwilling to eat, drink, and swallow and may also have swollen lymph nodes and fever. Sometimes these children become so dehydrated that they require hospitalization. In adolescents and adults, primary HSV-1 infection may present as tonsillitis. The tonsils may be tender and covered with a whitish substance, resembling a “strep throat”. The swelling and tenderness of the tonsils may result in swallowing difficulties.

Sometimes blisters may also be present in the mouth. In people with normal immunity (immunocompetent) the fever will cease and lesions will heal and crust over in a week. Even when no clinical symptoms of primary HSV-1 infection are apparent, some people will shed virus making them infectious.

The skin.

HSV-1 can also infect skin, but only if the skin is damaged, such as in patients with eczema (atopics). In rare instances, primary HSV-1 infection may become wide-spread in many areas of eczema across the body (eczema herpeticum). This condition requires antiviral treatment to limit its proliferation. Children who are thumb-sucking may develop herpes on their finger. Healthcare workers, such as anesthesiologists and dentists, may also infect their fingers (digits) from patients with cold sores or oral viral shedding. Herpes infection of the finger is called herpetic whitlow. In the immunocompetent patient, most skin lesions will heal within a few weeks, unless there is a complication with a bacterial infection such as Staphylococcus aureus or Group A Streptococcus, which may require antibiotic treatment.

Primary HSV-1 infection has also been associated with a variety of other skin disorders, such as erythema multiforme and Stevens-Johnson syndrome. These conditions are not thought to be directly caused by the virus, but result from an immunological reaction in the skin at the time of infection.

The eye.

A less common but clinically important primary HSV-1 infection site is the eye. Such infection may occur in one or both eyes as conjunctivitis, or as infection of the eyelid with blisters on the lid margin, swelling of the eyelids, and tearing. The eye itself may also be more extensively involved (keratoconjunctivitis). Occasionally, children with labial herpes or herpetic whitlow may rub their eyes and spread the virus to their eyes in this fashion (autoinoculation).In immunocompromised patients, HSV-1 eye infection may also involve the retina.

Neonatal herpes.

This is primary infection in the neonate, but is discussed under a separate heading below, in conjunction with herpes infection in pregnancy.

Primary HSV-1 infection summary
  • Most primary infections are asymptomatic
  • Asymptomatic shedding may occur in 2-9% of adults and 5-8% of children
  • If clinical symptoms occur they are usually mild
  • Some individuals will have severe symptoms.

Recurrent HSV-1 infections

Cold sores.

Approximately a quarter to a third of HSV-1 seropositive individuals will reactivate the virus. A common and well known sign of HSV-1 reactivation is the cold sore. Most individuals who suffer from recurrent cold sores will be aware of it 1-2 days prior to eruption by a feeling of tingling, itching, or pain (the prodrome) at the usual cold sore site. The cold sore often occurs in the same location, such as the upper lip, lower lip, or inside the mouth, but it may also be located on the nose, chin, or cheek. Individuals may sometimes experience recurrences in more than one location.

The exact underlying molecular mechanisms for virus reactivation are unknown, but we know that stress, extreme sunlight (beach activities, skiing), fever, local skin trauma, and menstruation are some of the factors that may contribute to the eruption of cold sores. The blisters in a cold sore contain infectious virus but usually heal within a few days, with or without causing ulcers that crust over. Cold sores are rarely associated with fever or other systemic symptoms.

The skin.

HSV-1 may reactivate in a finger as herpetic whitlow. Herpetic whitlow is often extremely painful, due to the presence of many sensory nerve endings and rigid skin in the finger tip.

The eye.

HSV-1 may reactivate in the conjunctiva of the eye (keratoconjunctivitis, herpes dendriticum) and may occasionally involve both eyes. Frequent recurrences may lead to scarring, thickening of the cornea, and uveitis and is the leading cause of blindness in the developed world. In the immunocompromised person, the retina may be involved and cause sudden blindness.

Neurologic symptoms.

Facial nerve paralysis (Bell’s palsy) has been associated with HSV-1 reactivation. In rare instances, HSV-1 can also infect the brain (herpes encephalitis). This infection may be associated with headache and increasing confusion and, if left untreated, the patient may rapidly become unconscious and die. It is not known how and why herpes encephalitis occurs. Some suggest that it represents reactivation of virus that is already latent in the brain; others suggest that it may spread from the nose or oral region through the olfactory nerve to the brain. Whatever the mechanisms, this condition requires early clinical recognition, laboratory testing, CT scans and prompt antiviral treatment.

Recurrent HSV-1 infections summary:
  • Tingling, discomfort, or itch (prodrome) occurs in approximately half of individuals just before the appearance of blisters.
  • In most people, the prodrome symptoms last for about a day before the outbreak of the actual cold sore. Some people will also feel fatigued for a couple of days beforehand
  • Sunlight, fever, local skin trauma, stress, and menstruation may be trigger factors for cold sores