Varicella-Zoster Virus (Chickenpox)

Chickenpox or varicella is a contagious disease caused by the varicella-zoster virus (VZV). The virus is responsible for chickenpox (usually primary infection in non-immune hosts) and herpes zoster or shingles (following reactivation of latent infection). Chickenpox results in a skin rash that forms small, itchy blisters, which scabs over. It typically starts on the chest, back, and face then spreads. It is accompanied by fever, fatigue, pharyngitis, and headaches which usually last five to seven days. Complications include pneumonia, brain inflammation, and bacterial skin infections. The disease is more severe in adults than in children. Symptoms begin ten to 21 days after exposure, but the average incubation period is about two weeks.

Chickenpox is a worldwide, airborne disease that is spread by coughing and sneezing, and also by contact with skin lesions. It may start to spread one to two days before the rash appears until all lesions are crusted over. Patients with shingles may spread chickenpox to those who are not immune through blister contact. The disease is diagnosed based on the presenting symptoms and confirmed by polymerase chain reaction (PCR) testing of the blister fluid or scabs. Tests for antibodies may be performed to determine if immunity is present. Although reinfections by varicella may occur, these reinfections are usually asymptomatic and much milder than the primary infection.

The varicella vaccine was introduced in 1995 and has resulted in a significant decrease in the number of cases and complications. It prevents about 70% to 90% of infections and 95% of severe disease. Routine immunization of children is recommended. Immunization within three days of exposure may still improve outcomes in children.