What is the Varicella Zoster Virus “Chicken Pox"?

.Varicella (chickenpox) is an acute infectious disease caused by varicella-zoster virus (VZV), which is a DNA virus that is a member of the herpesvirus group.

. Primary infection with VZV causes varicella. After primary infection as varicella (chickenpox), the virus remains dormant in the

sensory-nerve ganglia and can reactivate at a later time, causing herpes zoster (shingles).

. People at risk for severe varicella include: Immunocompromised people without evidence of immunity to varicella; Pregnant women without evidence of immunity to varicella; Newborns whose mothers have varicella from 5 days before to 2 days after delivery; Premature babies exposed to varicella or herpes zoster.

. Average incubation period: 14 to 16 days after exposure to a varicella or a herpes zoster rash. (Range from 10 to 21

days).

. Clinical features: A mild prodrome of fever and malaise may occur 1 to 2 days before rash onset, particularly in adults.

In children, the rash is often the first sign of disease. In unvaccinated people, varicella progresses rapidly from macular to papular to vesicular lesions before crusting.

. The most common chickenpox complications are bacterial infections of the skin and soft tissues in children and pneu-

monia in adults.

How is it spread?

. The virus can be spread from person to person by direct contact, inhalation of aerosols from vesicular fluid of

skin lesions of acute varicella or zoster; and possibly through infected respiratory secretions that also may be aerosolized.

. A person with varicella is considered contagious beginning 1 to 2 days before rash onset until all the chickenpox

lesions have crusted. Vaccinated people may develop lesions that do not crust. These people are considered conta-

gious until no new lesions have appeared for 24 hours.

Where is it found?

Humans are the only known reservoir for the varicella-zoster virus (VZV)

Prevention and Control?

Vaccination: 2 doses of varicella vaccine for all children, adolescents, and adults without evidence of immunity to varicella.

Isolation: Standard, airborne (negative air-flow rooms), and contact precautions until lesions are dry and crusted.

If negative air-flow rooms are not available, patients with varicella should be isolated in closed rooms. They should have no contact with people without evidence of immunity.

Patients with varicella should be cared for by staff with evidence of immunity.