Varicella (Chickenpox)

381 cases in 2024 — near the 5-year baseline of ~520.

What is it?

Varicella (chickenpox) is caused by the varicella-zoster virus (VZV). NYS had 381 cases in 2024, predominantly in unvaccinated individuals. The disease was once nearly universal in childhood before the vaccine era. The same virus causes shingles (herpes zoster) later in life when it reactivates. Chickenpox can be severe during pregnancy, leading to serious fetal complications.

How it spreads

One of the most contagious diseases known — spreads through airborne respiratory droplets and direct contact with blister fluid. Contagious from 1–2 days before the rash appears until all blisters have crusted over (usually 5–7 days). Can spread via airborne route across rooms.

Symptoms

Characteristic itchy, blister-like rash that appears in crops starting on the face, chest, and back before spreading to the rest of the body. Fever, fatigue, and loss of appetite typically precede the rash by 1–2 days. Complications include bacterial skin infections, pneumonia, and encephalitis, which are more common in adults and immunocompromised individuals.

Who is at risk?

Unvaccinated individuals of all ages. Adults who get chickenpox tend to have more severe illness than children. Pregnant people, newborns, and immunocompromised individuals face the highest risk of serious complications.

What you can do

Vaccine information

Two-dose varicella vaccine series (Varivax) is about 90% effective against any chickenpox and over 99% effective against severe disease. Also prevents shingles in vaccinated children. Zoster vaccine (Shingrix) is recommended for adults 50+ to prevent shingles.

Based on NYSDOH annual communicable disease report. Threat level reflects 2024 case counts compared to the 5-year baseline.