What is varicella?
What is varicella?
Varicella (commonly known as chickenpox) is caused by varicella-zoster virus. It usually occurs in childhood and is characterized by a generalized pruritic vesicular rash and fever.1
What are the symptoms of varicella zoster and its manifestations?
What are the symptoms of varicella zoster and its manifestations?
Symptoms that develop prior to the onset of rash include malaise, pruritus, anorexia, and listlessness.1,2
Skin manifestations in varying stages of evolution consist of maculopapules, vesicles, pustules, and scabs.1,2
At first, the lesions contain clear fluid, pustulating and scabbing over a short period of time. Rash initially appears on the trunk and face, quickly spreading to other areas of the body. Successive crops of lesions generally continue over a period of 2 to 4 days. Crusts completely fall off within 1 to 2 weeks after infection begins and can leave a slightly depressed area in the skin.1,2
How is varicella transmitted?
How is varicella transmitted?
The most common mode of transmission of varicella-zoster virus is believed to be person to person from infected respiratory tract secretions containing the varicella-zoster virus that come into contact with the mucosa of the upper respiratory tract or the conjunctiva of the eye.1 The virus is believed to replicate at the site entry in the nasopharynx and in regional lymph nodes. Varicella is usually contagious from 1 to 2 days before onset of rash until lesions have formed crusts.1
What are the clinical features of varicella over time?
What are the clinical features of varicella over time?
Pathogenesis of varicella
1. INFECTION DAY 0
2. PRIMARY VIREMIA
DAY 4–6


How is varicella diagnosed?
How is varicella diagnosed?
A varicella diagnosis can be typically based on:
Age of the patient1 |
Exposure to someone with varicella or herpes zoster within the last 2–3 weeks1,5 |
Season during which the rash occurs (In the United States, the incidence of varicella is highest between March and May.)1 |
Rash that:
|
What are the complications of varicella?
What are the complications of varicella?
Possible Varicella Complications | ||
---|---|---|
Cutaneous | Neurologic | Pneumonic |
Possible Varicella Complications |
---|
Cutaneous |
Neurologic |
Pneumonic |
What happens if a pregnant woman contracts varicella?
What happens if a pregnant woman contracts varicella?
There is a risk of congenital varicella syndrome if the mother contracts varicella in the first 20 weeks of pregnancy. Infant abnormalities include low birth weight, skin scarring, hypoplasia of an extremity, localized muscular atrophy, chorioretinitis, encephalitis, brain atrophy, and death.1,6
If the mother contracts varicella during the perinatal phase, varicella can infect the infant by transplacental viremia (intrauterine exposure), ascending infection during birth, or direct contact with infectious lesions after birth.10
Varicella during the first 12 days of life is attributed to intrauterine exposure, whereas infection after 12 days of birth is attributed to postnatal infection, given a rough 12-day incubation period in the neonate.10
Maternal disease between 20 to 6 days before delivery, or neonatal onset from 5 to 10 days post delivery has resulted in somewhat mild outcomes as infants have had a chance to acquire maternal antibodies to avoid long-term complications. However, maternal disease between 5 days before to 2 days after delivery, or neonatal onset from 5 to 10 days after delivery has resulted in fatal outcomes in 20%-23% of the cases reported.10
Premature neonates aged <28 weeks gestation at birth have a high risk of severe varicella during the first 6 weeks after birth as there appears to be no protective maternal antibodies because of reduced gestational period.10
How does geography affect the disease epidemiology of varicella?
How does geography affect the disease epidemiology of varicella?
![]() Temperate
Climates |
In regions with warmer summers and cooler winters, 90% of the population is infected with varicella prior to adolescence. Peak incidence of varicella typically occurs in the cooler months of the year (ie, winter or spring).1,11 |
![]() Tropical
Climates |
In tropical climates, adolescents and adults more commonly get varicella.11 |
Has the prevalence of varicella changed since the introduction of the varicella vaccine?
Has the prevalence of varicella changed since the introduction of the varicella vaccine?
From 1995 to 2010 in the US surveillance sites of West Philadelphia, PA and Antelope Valley, CA, there was a12:
~98% decline in the number of varicella cases at both surveillance sites since 1995
>85% decline in the number of varicella-related hospitalizations in 2006-2010, compared with 1995-1998
Downloadable Resource
The resource below has been created to help your patients, their parents, or their legal representatives, learn about varicella while they wait in the doctor’s office.
CDC Disease Information
DISCLAIMER: By clicking on the link below, you will be directed away from MerckVaccines.com to another website. Merck does not review or control the content of the site to which the hyperlink connects; therefore, the hyperlink does not constitute an endorsement by Merck.
CDC, Centers for Disease Control and Prevention
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference
Reference