Varicella Zoster Infection

Key facts

• Varicella zoster virus (VZV) causes chickenpox on first exposure, usually in childhood, and can reactivate later in life as shingles (herpes zoster).
• Chickenpox is a highly contagious rash illness; shingles is a painful, blistering rash that follows a single nerve path on one side of the body.
• First-line treatment is the antiviral aciclovir, most effective when started within 72 hours of the rash appearing.
• Seek urgent care if the rash involves the face or eye, or if severe symptoms develop in someone who is immunocompromised.

What VZV causes

Varicella zoster virus is responsible for two distinct illnesses. The first encounter, usually in childhood, produces chickenpox: a highly contagious rash of itchy, fluid-filled blisters that spreads easily before the spots even appear. Most children recover within one to two weeks, though the virus never fully leaves the body. It retreats to nerve tissue near the spine and can reactivate years or decades later as shingles (herpes zoster), a painful, blistering rash that follows a single nerve path on one side of the body. Reactivation becomes more likely with age, stress, or a weakened immune system.

Symptoms

Chickenpox starts with a mild fever and general unwellness before the rash appears, spreading in crops over several days. Shingles usually begins with burning or tingling pain in a band on one side of the trunk or face, followed a few days later by a blistering rash in that same area. The pain can persist after the rash heals, a complication called post-herpetic neuralgia.

Antiviral treatment

Both chickenpox and shingles respond to antivirals. Aciclovir is the established first-line agent: it works by blocking viral DNA replication, which reduces the duration and severity of the rash and, in shingles, lowers the risk of post-herpetic neuralgia. Treatment works best when started within 72 hours of the rash appearing, so prompt assessment matters more than waiting to see how it progresses.

When to see a doctor

Seek care urgently if the rash involves the face or eye, if you develop confusion or weakness, or if symptoms are severe in someone who is immunocompromised. Otherwise, see a doctor as soon as a shingles rash appears, since early antiviral treatment gives the best chance of a shorter illness and less lingering pain.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.