About Varicella-Zoster
Understanding Varicella
Varicella (chickenpox) is an acute infectious disease caused by the varicella zoster virus (VZV), a DNA virus belonging to the herpesvirus group. Following primary infection, VZV establishes latency within the sensory nerve ganglia. Primary infection with VZV results in Chickenpox, while reactivation of latent infection leads to the development of shingles.1
Although the use of the varicella vaccine has reduced the frequency of chickenpox, the virus has not been eradicated. Chickenpox outbreaks continue to occur even in settings such as schools where most children are vaccinated. 2, 3
This is particularly relevant for high-risk patients who are more susceptible to severe disease and complications.4
Symptoms
Individuals who have not contracted varicella, lack evidence of immunity, nor received the varicella vaccine, are susceptible to the disease.
A chickenpox rash typically lasts 4 to 7 days and is characterized by itchy, fluid-filled blisters that eventually crust over.
The rash initially manifests on the chest, back, and face before spreading throughout the body to include surfaces like the mouth, eyelids and genital area.
The onset of other common symptoms, such as fever, fatigue, decreased appetite, and headache, may precede the rash by one to two days.5
Definition of Exposure 6, 7
Close contact with an infectious person may include close indoor contact (e.g., in the same room) or face-to-face contact. Experts differ in their opinion about the duration of contact; some suggest 5 minutes and others up to 1 hour.
Varicella zoster virus exposure that may result in infections includes:
Exposure to Chickenpox patients
that are likely to result in infection include:
- Household exposure: infected contact residing in the same household
- Face-to-face indoor play of 5 minutes or more (some experts suggest >1 hour as the threshold for significant exposure through direct contact)
- Hospital exposure
Exposure to Shingles patients
that are likely to result in infection include:
- Close contact, such as touching or hugging
- Transmission has been seen to occur even when an HZ rash is covered
Facts
In the US, the incidence of VZV infection has decreased dramatically since the introduction of the varicella vaccine in 1995; however, suboptimal vaccination rates contribute to outbreaks and an increased risk of VZV exposure.8, 9, 10
As of 2023, the national Varicella Vaccine coverage for children by age 24 months was approximately 91%10
Increasing rates of under-vaccination and vaccine hesitancy in recent years are associated with vaccine-preventable disease outbreaks1
Vaccination disparities exist between foreign-born and US-born population12
Outbreaks of vaccine-preventable diseases are more likely to occur in areas where nonimmunized patients are clustered13
Varicella Zoster
Exposure Complications
High-risk individuals exposed to VZV can result in severe or complicated varicella, including pneumonitis, encephalitis, and hepatitis. Non-immune adults,
immunocompromised patients, and preterm infants are at highest risk of developing severe or complicated varicella. 14
Immunocompromised patients without evidence of immunity to Varicella
Varicella is likely to be severe in patients whose immunity is compromised, either due to a congenital immunodeficiency, transplantation, or various treatments for malignant or autoimmune disease. These patients are particularly prone to develop pneumonia and hepatitis due to VZV, which may be fatal.15
Preganant women without evidence of immunity to Varicella
Pregnant individuals who contract varicella (chickenpox) face a heightened risk of serious complications, most notably pneumonia, which can be severe and occasionally fatal. Some research indicates that both the occurrence and severity of varicella-related pneumonia are greater when the infection is acquired in the third trimester; however, this finding is not consistently supported across all studies.16
Infants without evidence of immunity to Varicella
Children born to pregnant women who develop varicella are at risk of sequelae from congenital varicella syndrome, depending on the timing of exposure during pregnancy. Newborn infants whose mothers develop varicella within 5 days before delivery or within 48 hours after delivery are at particularly high risk of severe varicella, likely due to the absence of protective transplacental VZV antibodies before birth.14