Infectious diseases | Varicella-zoster virus

Varicella-zoster virus (VZV) is the cause of varicella, also known as chicken pox, as well as zoster or shingles.

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Varicella-zoster virus (VZV) is a member of the Herpesviridae family of viruses, which are large DNA viruses. VZV belongs to the Alphaherpesvirinae subfamily and is also called human herpesvirus type 3 (HHV-3). VZV is the cause of varicella, also known as chicken pox, a common childhood illness that causes an itchy rash and vesicles (e.g., blisters or pox) all over the body. The first symptoms of chickenpox can include:

  • Fever
  • Headache
  • Sore throat
  • Fatigue
  • Loss of appetit

Skin lesions follow in one to two days.


Prior to the development of the varicella vaccine, chicken pox occurred in over 90 percent of children. Chicken pox can be severe in pregnant women, adults and people who have immune deficiency syndromes. Following chicken pox, VZV remains in a latent, or inactive, state in nervous tissue (dorsal root ganglia), but it can reactivate following periods of stress or many years following chicken pox as immunity wanes. Reactivation usually occurs in nerves that supply a single region of the body or dermatome. This reactivated VZV infection is called zoster or shingles and presents with severe pain associated with vesicles that occur on the face or trunk. The reactivation of VZV can also cause severe infections of the nervous system including meningitis and encephalitis.

Chicken pox or varicella is a highly contagious infection and is transmitted by respiratory secretions by coughing or sneezing. Fluid from a chicken pox blister is also infectious.

Shingles can be transmitted by close contact with vesicles to a non-immune person who has never been exposed to VZV and can thus lead to chicken pox.

Vaccination is recommended to prevent chicken pox and shingles. There is a live attenuated (weakened) varicella vaccine, which is highly effective at preventing chicken pox and recommended for children 18 months to adolescence. The zoster vaccine is recommended to prevent shingles for persons over 50 years old as well as those 19 years and older who have a weakened immune system.

An individual who has been infected with VZV will develop antibodies to the virus that will stay in the body for the rest of that person’s life. A blood test for these antibodies can tell whether a person has been infected sometime in the past with varicella-zoster virus. VZV can be detected in lesions by direct fluorescent antibodies and fluorescent microscopy or by polymerase chain reaction (PCR).

There’s no cure for VZV, and treatment for the virus generally is not recommended for healthy patients. Newborns and patients with encephalitis or a compromised immune system do need treatment for VZV infection. Antiviral drugs, such as acyclovir, slow down the virus reproduction and reduce symptoms but cannot eliminate the virus.

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