Chickenpox (Varicella Zoster)
- Highly contagious, generalized exanthem characterized by crops of pruritic vesicles on the skin and mucous membranes following exposure to varicella-zoster virus (VZV)
- VZV is acquired through inhalation of respiratory droplets from an infected host and through direct contact with vesicles.
- VZV establishes latency in the dorsal root ganglia; reactivation results in herpes zoster (shingles).
- Outbreaks tend to occur late winter through early spring in temperate climates.
- Usual incubation period is 14 to 16 days (range 10 to 21 days) after exposure to varicella OR shingles rash. Patients are infectious from ~48 hours before appearance of vesicles until the final lesions have crusted.
- Historically, most acquire chickenpox during childhood and developed lifelong immunity. The varicella vaccine became available in 1995 (1). Varicella is currently part of recommended primary vaccination schedule for children.
- System(s) affected: nervous, skin/exocrine
- Peak incidence 3 to 9 years but may occur at any age
- Predominant gender: male = female
- Decreasing incidence since routine vaccination; estimated 3.5 million cases annually prior to vaccine, with an incidence of 8–9% in children aged 1 to 9 years
- Reported U.S. varicella cases: 1991: 147,076; 2017: 8,775 cases (1)
- Prior to vaccine, ~100 deaths per year were reported in the United States; in 2015, only 6 reported deaths (1)
- U.S. rates: 1994, prior to vaccine: 136/100,000 persons; 2013 to 2014: <0.001/100,000 persons
- In developing countries, varicella is still associated with a severe disease burden.
- Susceptible (nonimmune) individuals exposed to varicella are at risk to develop disease and are also potentially infectious for 21 days.
Etiology and Pathophysiology
- Viral particles are inhaled via respiratory droplets where they invade respiratory epithelium. Replication in regional respiratory tract lymph nodes is followed by primary viremia (4 to 6 days after exposure). A second phase of viral replication and a secondary viremia (14 to 16 days after exposure) contributes to epidermal invasion and the characteristic skin lesions.
- Skin lesions are histologically identical to herpes simplex virus.
- In fatal cases, intranuclear inclusions are found in vascular endothelium and most organs.
- VZV is a double-stranded DNA virus of the α-Herpesviridae subfamily.
- Humans are primary disease reservoir.
Nonimmune, immunocompromised (especially children with leukemia/lymphoma in remission or receiving high-dose corticosteroids), pregnancy
- Infection is more severe in adults; reactivation of latent infection causes shingles.
- The CDC recommends vaccinating all immunocompetent adults ≥50 years old with recombinant varicella vaccine (Shingrix). The live attenuated vaccine (Zostavax) is no longer available for use in the United States as of 2020.
- The recombinant zoster vaccine (Shingrix) is administered as a 2-dose series separated by 2 to 6 months. This vaccine can be given to patients with a history of shingles or who have already had a dose of the live attenuated zoster vaccine.
- Primary viral pneumonia is the most common cause of death from varicella.
- Neonates born to mothers who develop chickenpox from 5 days before to 2 days after delivery are at risk for serious disease and should receive varicella-zoster immune globulin (VZIG).
- Newborns are at highest risk for severe disease during the 1st month of life, especially if mother is seronegative.
- Delivery prior to 28 weeks increases risk.
- Varicella bullosa is seen mainly in children <2 years. Lesions appear as bullae instead of vesicles. The clinical course is otherwise similar.
- Septic complications and encephalitis are the most common causes of death from zoster in children.
- Avoid aspirin/acetylsalicylic acid in children because of link to Reye syndrome.
- 25% risk of transplacental infection
- Congenital malformations are seen in 2% of patients when the fetus is infected during the 1st or 2nd trimester, characterized by limb hypoplasia, localized muscle atrophy, encephalitis, low birth weight, cutaneous scarring, cortical atrophy, chorioretinitis, and microcephaly.
- Morbidity (e.g., pneumonia) is increased in women infected during pregnancy.
- Women who contract chickenpox can breastfeed as normal. However, open vesicles on the breast should be covered to minimize transmission.
- Isolate hospitalized patients.
- When indicated, administer passive immunization using VZIG within 96 hours after exposure. VZIG recommended for:
- Patients exposed to chickenpox or shingles who are immunocompromised, newborns of mothers with onset of chickenpox <5 days before delivery or <2 days after delivery, premature infants (<28 weeks) exposed in neonatal period either whose mothers are not immune, or babies who weigh <1,000 g regardless of maternal immunity
- Active immunization prevents or reduces the severity of varicella if given within 72 hours of exposure.
- Active immunization: varicella virus vaccine (Varivax): live attenuated vaccine recommended by ACIP for immunization of healthy patients ≥12 months who have not had chickenpox
- ≥13 years: two 0.5 mL SC doses 4 to 8 weeks apart, seroconversion rates 78–82% after 1 dose, 99% after 2 doses; adult efficacy in lower end of this range
- 2014 U.S. estimate: 91% one or more dose vaccine coverage for children 19 to 35 months (3)
- Vaccine side effects include pain and redness at the vaccine site (19% of children; 24% of teens and adults). 1 in 10 develops fever. 1 in 25 will develop a mild varicella-like rash up to 1 month after vaccination.
- Vaccine contraindications
- Severe allergic reaction (e.g., anaphylaxis) to a previous dose or vaccine component
- Severe immunodeficiency (e.g., HIV patients with low CD4 counts, chemotherapy, congenital immunodeficiency, long-term immunosuppressive therapy)
- MMRV vaccine, combines the measles, mumps, and rubella vaccine with varicella, is equally effective. There are rare reports of an increased risk of febrile seizures 5 to 12 days after vaccination in 1/2,300 to 2,600 patients.
- May be considered for a subset of HIV-positive children in CDC class I with CD4 >25%
- Vaccine recipients who develop a rash should avoid contact with immunocompromised people, pregnant women who have never had chickenpox, and their newborns.
- Allow at least 3 months between doses 1 and 2 in children needing catch-up vaccination.
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Domino, Frank J., et al., editors. "Chickenpox (Varicella Zoster)." 5-Minute Clinical Consult, 27th ed., Wolters Kluwer, 2020. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688462/all/Chickenpox__Varicella_Zoster_.
Chickenpox (Varicella Zoster). In: Domino FJF, Baldor RAR, Golding JJ, et al, eds. 5-Minute Clinical Consult. Wolters Kluwer; 2020. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688462/all/Chickenpox__Varicella_Zoster_. Accessed May 31, 2023.
Chickenpox (Varicella Zoster). (2020). In Domino, F. J., Baldor, R. A., Golding, J., & Stephens, M. B. (Eds.), 5-Minute Clinical Consult (27th ed.). Wolters Kluwer. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688462/all/Chickenpox__Varicella_Zoster_
Chickenpox (Varicella Zoster) [Internet]. In: Domino FJF, Baldor RAR, Golding JJ, Stephens MBM, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2020. [cited 2023 May 31]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688462/all/Chickenpox__Varicella_Zoster_.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Chickenpox (Varicella Zoster) ID - 1688462 ED - Domino,Frank J, ED - Baldor,Robert A, ED - Golding,Jeremy, ED - Stephens,Mark B, BT - 5-Minute Clinical Consult, Updating UR - https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688462/all/Chickenpox__Varicella_Zoster_ PB - Wolters Kluwer ET - 27 DB - Medicine Central DP - Unbound Medicine ER -