What virus causes chickenpox?

What virus causes chickenpox? Varicella-zoster virus causes chickenpox.

Varicella-zoster virus, or VZV, is a human alphaherpesvirus. Its first infection usually produces chickenpox, also called varicella: an itchy rash of fluid-filled blisters accompanied by symptoms such as fever, tiredness, and headache. The incubation period is typically 10 to 21 days.

After the initial illness resolves, VZV is not necessarily eliminated. It can remain latent in sensory nerve ganglia for years or decades. If immunity later weakens, the virus may reactivate and travel along a nerve to the skin, causing shingles, also known as herpes zoster. Thus, chickenpox and shingles are different illnesses caused by the same virus at different stages.

VZV is often confused with herpes simplex virus because both belong to the herpesvirus family, but they are distinct viruses. The first live attenuated chickenpox vaccine was developed in Japan from the Oka strain in the 1970s. Routine vaccination has greatly reduced chickenpox cases and serious complications in countries that use it.