Varicella-zoster virus belongs to the herpes group of viruses and is the etiologic agent of varicella (chickenpox), the most common childhood disease associated with a rash. 

Epidemiology

1. Chickenpox occurs most frequently during childhood with about 90% of adults having evidence of seropositivity. 
2. Very contagious with about 80% of household contacts becoming infected. 
3. Approximately 200 deaths per year in the United States and 6000-9000 hospital admissions. 
4. Incubation period is 10-21 days and the contagious period is 1-2 days prior to the rash and about 5 days after the rash begins when all lesions are crusted.
5. Transmission is primarily from direct contact with patients who have varicella infection and occasionally by air-borne spread of droplets.
6. Immunity is lifelong with rare second cases reported. Most "second" cases are a result of a wrong primary diagnosis
7. After primary infection, the virus may be dormant in the dorsal root ganglion and become activated clinically as "shingles".

1. After a 1-2 day of mild prodromal symptoms, the child will break out with rash usually on the trunk. The rash will start as macular red lesions and proceed to papules, vesicles, pustules, and then crusted lesion. They come out in crops and there are lesions present of different stages. May have involvement of the mucous membranes and this may help distinguish chickenpox from insect bites
2. The rash is very pruritic but systemic symptoms are mild.
3. Teenagers and adults may become very ill with high fevers and the development of pneumonia.
4. Congenital varicella infections are rare because of the high incidence of maternal immunity. Pregnant woman who develop chickenpox during the first or second trimester may deliver a neonate with the congenital varicella syndrome. Findings may consist of limb anomalies, SGA, eye changes including chorioretinitis,cataracts, and scarring. 
5. Neonates born to mothers who acquire varicella 5 days prior to delivery or 2` days after delivery have a high incidence of serious infections and death. Treatment with VZIG has improved the outcome in these neonates. Neonates who develop varicella after this period are generaly not sicker than infants and older chldren. 
6. Infections in immunocompromised children are associated with life-threatening illness.

1. Secondary bacterial infections of skin lesions. Usually S.aureus or S.pyogenes. 
2. Necrotizing fasciitis may follow secondary infection with S.pyogenes
3. Secondary infections of the lung with S.pyogenes causing a severe pneumonia
4. Cerebellar ataxia- common after varicella infection
5. Encephalitis, aseptic meningitis, transverse myelitis
6. Primary varicella pneumonia
7. Reye syndrome- incidence decreased over past 15 years. Severe vomiting and mental status changes. Has beeen associated with the use of aspirin.
8. Hemorrhagic chickenpox. 
9. Shingles
1. results from reactivation of dormant virus in the dorsal ganglia. 
2. adults, there is usually no underlying condition that leads to reactivation. Lesions are mostly confined to the trunk. 
3. Follows dermatome distribution and rarely painful. Usually pruritic. 
4. Isolation unnecessary as long as lesions are covered. 
5. Highest incidence in children who had primary infection when they were less than one year of age. 

1. Antipruritic measures- Calamine lotion typically, soothing baths with the addition of oatmeal, and Benadryl PO. Keep the child's fingernails short.
2. May return to school after all the lesions are crusted, which is about 5-7 days after appearance.
3. Acyclovir- routine use in varicella not recommended. In immunocompromised hosts, teenagers, and adults, acyclovir may be given orally to help decrease the symptoms. It can be administered orally and should be started within 12 hours of the appearance of the first lesions.
4. Some new literature has demonstrated the effectiveness of post-exposure immunization in preventing the development of disease.

1. The immunization, a live attenuated vaccine, is recommended for all children by ACIP and the AAP between 12-18 months
2. Children <13 years need one dose and> 13, two doses 4-8 weeks apart.
3. May be given concomitantly with the MMR, but if given separately, one month apart
4. Excellent antibody response (95%) and immunity has not been shown to wane in follow-up studies of 10 years duration. 
5. Rare breakthrough cases of chickenpox in prior immunized individuals have been mild
6. Post vaccination rashes are uncommon and virus has rarely been isolated from these lesions
7. Vaccine should not be given to immunocompromised hosts including patients receiving chemotherapy, or taking 2 mg./kg./day prednisone for greater than a month. 
8. HIV patients with mild or no symptoms and CD$=T-lymphocyte percentage > 25% may receive the vaccine.
9. Children in households with immunocompromised hosts or pregnant women, may receive the vaccine. If they break out with a rash, contact should be avoided with the immunocompromised individual. 
10. Patients receiving steroids should be off them for 1 month prior to giving the vaccine and the use of nasal or inhaled steroids is not a contraindication to the vaccine. 

1. Indications- should be given as soon as exposure occurs but may be effective if given 96 hours later.
1. Immunocompromised individuals
2. newborns of mothers who acquire varicella 5 days prior to or 2 days after delivery
3. Exposed premis < 28 weeks or < 1000 grams
4. Exposed premis > 28 weeks whose mother has not had chickenpox
5. Susceptible adults
6. Susceptible pregnant mothers. VZIG may decrease symptoms in the pregnant mother but the virus may still be transimitted to the fetus.

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<>NEJM March 15, 2007
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