Difference Between Varicella and Zoster

The key difference between varicella and zoster is that the varicella (or chicken pox) is the primary viral infection by the varicella zoster virus whereas the zoster (or shingles ) is the reactivation of the latent viral infection.

Firstly, Varicella zoster virus causes two main forms of diseases as varicella and zoster. Varicella is the primary infection by the varicella zoster virus. However, after the initial infection, varicella zoster virus can remain dormant in the dorsal root ganglia of sensory nerves and get reactivated whenever the person’s immunity weakens. Shingles or zoster refers to the reactivation of the varicella zoster virus in this manner. Therefore, varicella is the primary viral infection whereas zoster is the reactivation of the latent viral infection.

CONTENTS

1. Overview and Key Difference
2. What is Varicella 
3. What is Zoster
4. Similarity Between Varicella and Zoster
5. Side by Side Comparison – Varicella vs Zoster in Tabular Form
6. Summary

What is Varicella?

Varicella or chicken pox is the primary infection by the varicella zoster virus. Most patients contract the disease during their childhood by the inhalation of respiratory droplets contaminated with the virus. The infectivity of the virus is highest from 2 days before the appearance of the rash to the disappearance of the skin lesions. With the onset of the recovery phase, the virus remains dormant in the dorsal root ganglia.

Clinical Features

• There is an incubation period of 14-21days after which the symptoms appear.
• Initially, there are constitutional symptoms such as fever, headache, and malaise
• A macular rash appears after the prodromal symptoms, which ends up as a pustular rash within few hours.
• The severity of the illness increases with age. Young children have only mild symptoms, but in the adults, the disease can be debilitating.
• The skin lesions usually resolve without leaving scars.

Complications

• Pneumonia which appears about 6 days after the appearance of the skin lesions
• Bacterial infection of the skin lesions
• Intrauterine infection in pregnant women
• Disseminated infection in the immunocompromised patients

Diagnosis of varicella is usually through clinical manifestations. Viral DNA studies can be done for the identification of the presence of the virus within the vesicular lesions.

Treatment

Chickenpox in children does not require any treatment. All adult patients above the age of 16 years require antiviral therapy with acyclovir. Any patient with an immune deficiency should be treated with immunoglobulins.

What is Zoster?

After the initial infection, varicella zoster virus can remain dormant in the dorsal root ganglia of sensory nerves; however, reactivate whenever the person’s immunity weakens. The reactivation of the varicella zoster virus in this manner is called shingles or zoster.

Clinical Features

• Usually, there is a burning sensation or a pain in the affected dermatome. A rash characterized by the presence of vesicles appears in this region with distant chicken pox-like
• Sometimes paresthesia can exist without any associated dermatological manifestations
• Multi dermatomal involvement, severe disease and prolonged duration of the symptoms suggest underlying immune deficiencies such as HIV.

Usually, the reactivation of the virus commonly affects the thoracic dermatomes. Vesicles can appear in the cornea when there is a reactivation of the virus in the ophthalmic division of the trigeminal nerve. These vesicles can rupture, giving rise to corneal ulcerations which require the immediate attention of an ophthalmologist to avoid blindness.

Reactivation of the viruses in the geniculate ganglion can cause the Ramsay Hunt syndrome, which has the following hallmark features.

• Facial palsy
• Ipsilateral loss of taste
• Buccal ulceration
• A rash in the external auditory canal

When the sacral nerve roots are involved there can bladder and bowel dysfunction.

Other Rare Manifestations

• Cranial nerve palsies
• Myelitis
• Encephalitis
• Granulomatous cerebral angiitis

There can be postherpetic neuralgia in some patients for about six months after the reactivation. The incidence of postherpetic neuralgia increases with advanced age.

Management

• Treatment with acyclovir can be useful in minimizing the pain
• Strong analgesic agents and other drugs such as amitriptyline help to relieve the pain due to postherpetic neuralgia.

What is the Similarity Between Varicella and Zoster?

• Both diseases are caused by the varicella zoster.

What is the Difference Between Varicella and Zoster?

Varicella is the primary infection by the varicella zoster virus. However, after the initial infection, the varicella zoster virus can remain dormant in the dorsal root ganglia of sensory nerves and get reactivated whenever the person’s immunity weakens. Zoster thus refers to the reactivation of the varicella zoster virus in this manner. This is the main difference between varicella and zoster.

There is an incubation period of 14-21days in varicella after which the symptoms appear. Initially, there are constitutional symptoms such as fever, headache, and malaise. Then, a macular rash appears after these prodromal symptoms, which ends up as a pustular rash within few hours. Moreover, the skin lesions usually resolve without leaving scars. Most importantly, the severity of the illness increases with age. In zoster, there is usually a burning sensation or a pain in the affected dermatome. A rash characterized by the presence of vesicles appears in this region with distant chicken pox-like lesions. Furthermore, multi dermatomal involvement, severe disease and prolonged duration of the symptoms suggest underlying immune deficiencies such as HIV.

Chickenpox/varicella in children does not require any treatment in the immune competent patients. All adult patients above the age of 16 years require antiviral therapy with acyclovir. Any patient with an immune deficiency should be treated with immunoglobulins. However, in zoster, treatment with acyclovir can be useful in minimizing the pain. Furthermore, strong analgesic agents and other drugs such as amitriptyline can relieve the pain due to postherpetic neuralgia.

Summary – Varicella vs Zoster

Varicella or chicken pox is the primary infection by the varicella zoster virus. After the initial infection, varicella zoster virus can remain dormant in the dorsal root ganglia of sensory nerves and get reactivated whenever the person’s immunity weakens. The reactivation of the varicella zoster virus in this manner is called shingles or zoster. So, varicella is the primary infection by the varicella zoster virus and zoster is the reactivation of the latent viral infection. This is the most distinct difference between varicella and zoster.

Reference:

1. Kumar, Parveen J., and Michael L. Clark. Kumar & Clark clinical medicine. Edinburgh: W.B. Saunders, 2009.

Image Courtesy:

1. “Day05 shingles or Herpes Zoster Virus attacking forehead and eye” By Burntfingers – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Varicella” by Noj Han (CC BY-SA 2.0) via Flickr