Herpes Zoster

Varicella infection generally results in permanent immunity in immunocompetent individuals, but the virus is not eliminated from the body and remains latent in the nerve ganglia of the spinal roots. The latent virus may undergo reactivation in about 10-20% of cases, an event that usually occurs in individuals around the age of 50 years. Reactivation of the virus results in the onset of Zoster or shingles, which manifests as a rash at the level of the dermatomeres corresponding to the latency ganglion, usually monolaterally. The skin lesions at the level of the affected dermatomeres are termed cluster lesions of vesicular type. The symptomatology of this condition is pain at the level of the eruption, often very intense accompanied by burning and itching. This condition can also result in the onset of systemic symptoms such as fever, headache, and fatigue. In the event that pain related to this condition persists for more than a month, it is referred to as "post-herpetic neuralgia."

Chickenpox is an endemic disease worldwide, and infection, in the absence of vaccination, tends to occur in childhood. The epidemiology of this infection differs between temperate and tropical areas, probably due both to characteristics peculiar to the virus such as sensitivity to heat and to characteristics peculiar to the area such as population density and hygiene conditions. In Italy, the estimated incidence is 99 cases per 100,000 inhabitants per year. The incidence of this disease has certainly been reduced since the introduction of the vaccine, which is administered together with rubella, measles and pertussis vaccine in infancy.

Diagnosis, for both chickenpox and Zoster, is usually clinical, possible because of the highly characteristic picture of signs and symptoms. Diagnostic laboratory tests, such as the detection of anti-varicella-Zoster IgM, are also available.lo.

With regard to chickenpox, therapy is usually only symptomatic. For flu-like symptomatology and fever, the recommended treatment is with acetaminophen; however, the use of salicylates, such as aspirin, should be avoided because of the increased risk of onset of Reye's syndrome in children. In cases of intense itching, antihistamines may be administered instead. In any case, practical precautions should be taken, such as avoidance of scratching to avert scarring lesions on the skin, and isolation of the sufferer to prevent spread of the disease. In individuals most at risk of complications, antiviral drugs such as Acyclovir can be used; in immunocompromised individuals this therapy should be given intravenously. With regard to Zoster, treatment should begin within 72h of the onset of first symptoms in immunocompromised subjects and is also strongly recommended in immunocompetent subjects presenting with intense pain or facial rash, especially around the eye. Treatment is with antiviral drugs such as Famciclovir or Valacyclovir with oral administration, which have been shown to have greater bioavailability than Acyclovir. In immunocompromised patients, however, there is an indication for intravenous administration of therapy. Regarding the therapeutic management of painful symptomatology, pain-relieving and anti-inflammatory drugs may be administered. On the other hand, the clinical management of symptomatology related to post-herpetic neuralgia is more complex and may require drugs such as Gabapentin and Pregabalin, tricyclic antidepressants, locally applied solutions based on local anesthetics such as lidocaine, and botulinum toxin injections. In cases of pain refractory to therapy, it may be necessary to switch to opioid painkillers or the use of intrathecal methylprednisolone.

Prevention of this disease is based on the administration of the Varicella-Zoster vaccine, which has been available since 1995 and administered together with the Measles, Rubella and Pertussis vaccine. This vaccine has been shown to be 95% effective in preventing moderate and severe forms and 70-75% effective in mild forms. It is a safe and well-tolerated vaccine. It is administered in two doses, one around 12-15 months of age and the second around 5-6 years of age. This vaccination is contraindicated in cases of demonstrated allergy to components of the vaccine and in cases of pregnancy; in fact, women who have had the vaccination should wait at least one month before becoming pregnant. On the other hand, vaccination is also recommended in older children or adults who have not yet developed the disease, as infection acquired in adulthood could lead to more serious clinical consequences. For individuals at high risk of contracting varicella in a severe form, such as fragile infants or immunocompromised individuals, treatment with intramuscular immunoglobulin is indicated if they have been exposed to infected persons, according to passive prophylaxis; this administration should take place as soon as possible and no later than 96 hours after exposure.