CHICKENPOX (VARICELLA ZOSTER)

CHICKENPOX (VARICELLA ZOSTER) - Kay A. Bauman, MD, MPH
BASICS
DESCRIPTION
A common, highly contagious generalized exanthem characterized by the development of crops of pruritic vesicles on the skin and mucous membranes
• Virus is spread by respiratory (airborne) droplets, direct contact with varicella vesicles, or rarely zoster lesions
• Virus establishes latency in the dorsal root ganglia; reactivation results in herpes zoster or "shingles"
• Outbreaks tend to occur late winter to early spring in temperate climates.
• The usual incubation period is 14-16 days (range, 10-21). Patients are infectious from ~48 hours before appearance of the rash until the final lesions have crusted. Most people acquire chickenpox during childhood and develop lifelong immunity. (1)
• System(s) Affected: Nervous, Skin/Exocrine
• Synonym(s): Varicella
ALERT
Geriatric Considerations
• Infection more severe than in children
• Latent varicella infection may reactivate and cause the exanthem known as shingles or zoster.
• Most common cause of death: Primary viral pneumonia
Pediatric Considerations
• Neonates born to mothers who develop chickenpox 5 days before or 2 days after delivery are at risk for serious disease. Must give varicella-zoster immune globulin
• Varicella bullosa seen mainly in children 2 years. Lesions appear as bullae instead of vesicles. The clinical course does not change.
• Most common cause of death: Septic complications and encephalitis
• Avoid aspirin/acetylsalicylic acid in children because of link to Reye disease
Pregnancy Considerations
• Risk of transplacental infection after maternal infection is 25%.
• Congenital malformations are seen in 2% (1) of patients when the fetus is infected during the 1st or 2nd trimesters; characterized by limb atrophy and scarring of the skin of the extremities and occasional CNS and eye manifestations
• Morbidity is increased in women infected during pregnancy (e.g., pneumonia).
GENERAL PREVENTION
• Exposed, susceptible people should be considered at risk and potentially infectious for 21 days.
• Isolation of hospitalized patients
• Passive immunization with IM varicella-zoster immune globulin given within 96 hours (preferably within 72 hours) of exposure to ensure efficacy. (1) Recommended for people exposed to chickenpox or shingles within 96 hours who are immunocompromised, 15 years old without prior history of chickenpox, newborns of mothers with onset of chickenpox 5 days before delivery or 2 days after delivery. Exposure criteria: Continued household contact, prolonged face-to-face contact (same room), or indoor playmate >1 hour
• Active immunization after exposure: Shown to prevent or reduce significantly the severity of varicella if given within 72 hours postexposure.
• Active immunization: Varicella virus vaccine (Varivax): Live attenuated vaccine approved by the Federal Drug Administration in 1995 for pediatrics immunization and recommended by the Advisory Committee on Immunization Practices for immunization of healthy patients 12 months who have not had chickenpox
- 12 months-12 years old: Single dose 0.5 mL SC. Seroconversion rates: 95% (1)
- 13 years: 2 0.5-mL SC doses 4-8 weeks apart, seroconversion rates 78-82% after 1 dose, 99% after 2 doses (1)
- May be considered for a subset of HIV-positive children in Centers for Disease Control and Prevention class I with CD4 >25% (1)
• Vaccine recipients should avoid contact with immunocompromised people and pregnant women who have never had chickenpox and their newborns, for up to 6 weeks after vaccination.
EPIDEMIOLOGY
• Predominant age: Peak incidence pre-schoolers to 9 years, but may occur at any age
• Predominant sex: Male = Female
Incidence
• Decreasing in incidence since vaccine available: Reported US varicella cases 1991: 147,076; reported for 2003: 20,948 (2,3)
• Prior to vaccine availability, approximately 100 deaths in the US/year were reported; for 2003 and the 1st 1/2 of 2004, only 8 deaths were reported (4).
RISK FACTORS
• No prior history of varicella infection
• Immunosuppressed patients (especially children with leukemia/lymphoma in remission or receiving high-dose corticosteroids)
Genetics
No known genetic pattern
ETIOLOGY
Varicella-zoster virus is a member of the alpha Herpesviridae subfamily; a double-stranded DNA virus; reservoir: Humans

DIAGNOSIS
SIGNS AND SYMPTOMS
• Prodromal symptoms: Fever, malaise, anorexia, and mild headache
• Characteristic rash: Crops of "teardrop" vesicles on erythematous bases
• Lesions erupt in successive crops.
• Progress from macule to papule to vesicle, then begin to crust
• Pruritic rash present in various stages of development.
• Lesions may be present on mucous membranes, both oral and vaginal.
• Malaise, muscle aches, arthralgias, and headache more common in adults (5)
• Subclinical in ~4% of cases (5)
TESTS
Generally used for complicated cases and epidemiologic studies
• Visualization of the virus by electron microscopy, tissue culture (costly), and various methods of acute and convalescent sera collection: Latex agglutination (most available), enzyme immunoassay, indirect immunofluorescence antibody, fluorescent antibody to membrane assay, or polymerase chain reaction assay, which can detect wild from vaccine viral strains (1)
Lab
• Leukocyte count may be normal, low, or mildly increased.
• Marked leukocytosis suggests secondary infection.
• Multinucleated giant cells visible on Tzanck smear from scrapings of vesicles
• Isolated virus from human tissue culture
Pathological Findings
• Skin lesions identical histologically to those of herpes simplex virus
• In fatal cases, intranuclear inclusions can be found in the endothelium of blood vessels and most organs.
DIFFERENTIAL DIAGNOSIS
• Herpes simplex virus infection
• Herpes zoster
• Impetigo
• Coxsackievirus infection
• Scabies
• Dermatitis herpetiformis
• Drug rash
• Rickettsialpox infection
TREATMENT
Outpatient except for complicating emergencies
GENERAL MEASURES
• Supportive/symptomatic treatment
• Good hygiene to avoid secondary infection
Diet
No special diet
Activity
As tolerated. Children may return to school when lesions have scabbed over, temperature is normal, and sense of well-being has returned.
MEDICATION (DRUGS)
First Line
• Antipyretics for fever; avoid aspirin in children
• Local and/or systemic antipruritic agents for itching
• In immunocompromised patients: Varicella-zoster immune globulin available for passive immunization. Varicella-zoster immune globulin must be given within 96 hours after exposure to be beneficial. After 4th day postexposure, wait for rash to develop, then give acyclovir 500 mg/m2/d q8h for 7 days.
• Acyclovir: Decreases duration of fever and shortens time of viral shedding. Recommended for adolescents, adults, and high-risk patients. Most beneficial if initiated early in the disease (24h).
- 2-16-year-old patients: 20 mg/kg/dose (max. 800 mg/dose), q.i.d. for 5 days
- Adults: 800 mg, 5 daily.
• Contraindications
- Hypersensitivity to the drug
• Precautions
- Possible renal insufficiency with acyclovir
• Significant possible interactions
- Concurrent administration of probenecid increases half-life; increased effects with zidovudine (e.g., drowsiness, lethargy)
Second Line
• Famciclovir: 500 mg t.i.d. for 7-10 days
• Valacyclovir: 1 g t.i.d. for 7-10 days
FOLLOW-UP
PROGNOSIS
• In the healthy child, chickenpox is rarely serious and recovery is complete.
• Confers lifelong immunity
• 2nd attack rare, but subclinical infection can occur; happens occasionally after vaccination in children
• Infection latent and may recur years later as herpes zoster in adults (and sometimes in children)
• Fatalities rarely occur from complications.
COMPLICATIONS
• Although only 2% of cases are reported after 2nd decade, 35% of deaths occur in the age group. (5)
• Secondary bacterial infection: Cellulitis, abscess, erysipelas, sepsis, septic arthritis/osteomyelitis, or staphylococcal pyomyositis
• Pneumonia: 20-30% of adults with chickenpox have lung involvement, 1/400 are hospitalized (5)
• Encephalitis (the most common central nervous system complication); meningitis
• Reye syndrome
• Purpura
• Thrombocytopenia
• Glomerulonephritis
• Arthritis
• Hepatitis
PATIENT MONITORING
Usually none needed in mild cases. If complications occur, intensive supportive care may be required.
REFERENCES
1. American Academy of Pediatrics. Report of the Committee on Infectious Diseases (Red Book). Elk Grove Village, IL: American Academy of Pediatrics; 2003.
2. Centers for Disease Control and Prevention. Summary of Notifiable Diseases, United States, 1991. Morbidity and Mortality Weekly Report. 1992;40(No. 53).
3. Centers for Disease Control and Prevention. Summary of Notifiable Diseases, United States, 2003. Morbidity and Mortality Weekly Report. 2005;52(No. 54).
4. Centers for Disease Control and Prevention. Varicella-Related DeathsUnited States, January 2003-June 2004. Morbidity and Mortality Weekly Report. 2005;54:272-274.
5. Goldman L, Bennett JC, ed. Cecil Textbook of Medicine, 21st Edition, Philadelphia, PA: WB Saunders 2000.