Varicella Zoster Virus Infection

Varicella zoster virus is a common virus that causes chickenpox when you first catch it, and can come back years later to cause shingles, a painful rash that affects adults.

Table of contents

• What is varicella zoster virus?
• Types of infections caused by VZV
• Symptoms of VZV infection
• How the virus spreads
• People at higher risk
• How VZV infections are diagnosed
• Treatment options
• Prevention through vaccination

What is varicella zoster virus?

Varicella zoster virus (VZV) is a type of herpes virus, which is a family of viruses that can infect humans. This particular virus is responsible for causing chickenpox and shingles, as well as several other less common conditions^[1].

What makes this virus unusual is that once you’re infected, it never completely leaves your body. After you recover from chickenpox, the virus stays hidden in your nerve cells, specifically in the dorsal root ganglia (nerve clusters near your spine) and sometimes in the trigeminal nerve (a nerve that runs through your face)^[1]. The virus remains inactive, or dormant, without making you sick. However, it can wake up later in life and cause new symptoms^[1].

VZV is highly contagious, meaning it spreads easily from person to person. It is specific to humans and cannot infect other animals^[3]. The virus can survive in the environment for a few hours, though it is considered fragile outside the body^[3].

Types of infections caused by VZV

Varicella zoster virus causes several different conditions depending on whether it’s your first infection or if the virus reactivates years later^[1].

Chickenpox (varicella) is the illness you get when you’re first infected with the virus. This is called the primary infection. It mainly affects children and causes an itchy rash with fluid-filled blisters all over the body^[1][5].

Shingles (herpes zoster) happens when the dormant virus reactivates, usually many years or even decades after you had chickenpox. About one in three people will develop shingles at some point in their lifetime^[3]. The risk increases significantly with age, with about one in two people aged 85 and older experiencing shingles^[3]. Shingles causes nerve pain and a painful rash that typically appears as a stripe of blisters on one side of the body^[8].

The virus can also cause more serious infections when it reactivates^[1]:

• Meningitis, encephalitis, and meningoencephalitis occur when VZV infects the brain or the protective layers covering it. Encephalitis, or brain inflammation, is a rare but serious complication affecting about 1 in 4,000 children with chickenpox^[4][22].
• Herpes zoster ophthalmicus, also called eye shingles, affects the area around the eye and forehead^[1].
• Ramsay-Hunt syndrome (herpes zoster oticus) happens when the virus reactivates in facial nerves, potentially causing facial paralysis, earache, and other symptoms^[1].

Symptoms of VZV infection

The symptoms you experience depend on which type of VZV infection you have and where in your body the virus is active^[1].

Common symptoms across different VZV infections include^[1]:

• Fever
• Rash with fluid-filled blisters
• Burning pain in the skin
• Headache
• Eye redness and swelling
• Sensitivity to light (photophobia)
• Facial paralysis
• Earache
• Toothache

With chickenpox, initial symptoms usually include a slight fever and feeling tired and weak. These are quickly followed by an itchy, blister-like rash^[7]. The rash typically appears on the face, scalp, and trunk first, with pink spots that develop into tiny fluid-filled blisters. These blisters eventually dry out and form scabs after four to five days^[7]. The blisters tend to be more common on covered parts of the body than exposed areas, and they may appear on the scalp, armpits, trunk, and even on the eyelids and in the mouth^[7].

After exposure to the virus, chickenpox has an incubation period (the time between catching the virus and showing symptoms) of 10 to 21 days, with an average of 14 days^[3][5]. The illness typically lasts about 3 to 4 days^[3].

With shingles, burning pain typically comes before the rash appears by several days, and this pain can continue for several months after the rash clears up^[14]. The rash and associated pain usually occur only on one side of the body, following the path of one or two adjacent sensory nerves^[3]. The skin lesions usually heal within several weeks, but the pain often lasts longer^[3].

How the virus spreads

Varicella zoster virus is extremely contagious. It spreads more easily than mumps and rubella, though not quite as easily as measles^[5].

During a chickenpox infection, the virus spreads through coughing, sneezing, and direct contact with the rash^[1]. The virus can travel through the air when people talk, laugh, cough, or sneeze, and it can also spread when items contaminated with saliva are shared, such as cups, bottles, or utensils^[7].

A person with chickenpox is most contagious 1 to 2 days before the rash appears and remains contagious until all the blisters have crusted over^[3][5]. For vaccinated people who develop chickenpox and have lesions that don’t form crusts, they are considered contagious until no new lesions have appeared for 24 hours^[5].

About 90% of people who are not immune and have close contact with someone who has chickenpox will become infected^[5][7]. Living in close quarters, such as dormitories or camps, increases the risk of the virus spreading^[7].

When someone has shingles, the virus spreads mainly through direct contact with the rash, and sometimes through virus particles from the rash that become airborne^[1]. An important point to understand is that you cannot catch shingles from someone who has it. However, if you’ve never had chickenpox and haven’t been vaccinated, you can catch chickenpox from someone with shingles^[1].

Studies of transmission in households show that the risk of catching VZV from someone with shingles is approximately 20% of the risk from someone with chickenpox^[5]. People with mild breakthrough chickenpox (fewer than 50 lesions) who were vaccinated are about one-third as contagious as unvaccinated people with chickenpox. However, vaccinated people with 50 or more lesions are just as contagious as unvaccinated individuals^[5].

People at higher risk

While chickenpox is often mild in healthy children, certain groups of people are at higher risk for severe illness and complications^[5][7]:

• People with weakened immune systems, such as those with HIV/AIDS or cancer, people who have had transplants, and those taking medications like chemotherapy, immunosuppressive drugs, or long-term steroids
• Pregnant women
• Newborn babies, especially those whose mothers develop chickenpox symptoms between 5 days before and 2 days after delivery
• Premature babies exposed to the virus
• Infants, adolescents, and adults

The risk of developing shingles increases with several factors. The most important is age—the risk of shingles roughly doubles in each decade after age 50^[4]. Other factors that increase the risk include taking immunosuppressive medications, having an illness or condition that weakens the immune system (like HIV or cancer), and being under significant stress^[1].

The risk of developing postherpetic neuralgia (persistent pain after shingles) also increases with age, occurring nearly 15 times more often in people over 50 years old^[14]. About 20% of people with shingles develop this complication, and in 10 to 15% of cases, the pain persists for more than three months^[3][14].

How VZV infections are diagnosed

Healthcare providers usually diagnose varicella zoster virus infections based on the appearance of the rash and other symptoms^[1]. The distinctive blister-like rash of chickenpox or the dermatomal pattern of shingles (appearing in a stripe along one side of the body) often makes clinical diagnosis straightforward.

However, laboratory testing can confirm the diagnosis when needed, especially in cases with unusual presentations or in people with weakened immune systems^[2]. Healthcare providers can take samples of fluid or tissue from the rash blisters and send them to a laboratory to test for the virus^[1].

The most reliable diagnostic method involves detecting VZV DNA in samples using laboratory techniques^[22]. Cultures can also be performed by collecting vesicular fluid and inoculating it onto specific cell types, though VZV is fragile and requires careful handling to minimize time in transport and storage^[11].

Treatment options

Treatment for VZV infections varies depending on the type of infection, the severity of symptoms, and whether the person has risk factors for complications.

For chickenpox in otherwise healthy children, treatment is often not routinely recommended due to the self-limiting nature of the infection^[15]. The illness typically resolves on its own within about a week^[1]. However, antiviral treatment may be considered for certain groups, including people over 12 years old who haven’t been immunized, those with chronic skin or lung conditions, and people receiving long-term salicylate or steroid therapy^[15].

At-home care measures can help relieve symptoms^[12][13]:

• Applying calamine lotion to the skin
• Taking cool baths with added baking soda, uncooked oatmeal, or colloidal oatmeal to ease itching
• Keeping fingernails trimmed short to minimize scratching
• Using body lotion or menthol lotion to relieve discomfort

For fever relief, non-aspirin medications such as acetaminophen can be used^[12]. It’s extremely important never to give aspirin to children with chickenpox, as this is associated with Reye’s syndrome, a severe disease that affects the liver and brain and can be fatal^[12].

Antiviral medications are the main treatment for more severe cases and for people at risk of complications^[12]. The three commonly used antivirals are:

• Acyclovir (available in oral and intravenous forms)
• Valacyclovir (oral)
• Famciclovir (oral)

These medications work best when started early, ideally within 24 hours after the rash appears and generally no later than 72 hours after rash onset^[9][12]. For chickenpox, the typical oral dose of acyclovir is 20 mg/kg (maximum 800 mg) four times daily for 5 days^[15]. Valacyclovir is often preferred when available, at a dose of 20 mg/kg (maximum 1,000 mg) three times daily^[15].

For people requiring hospitalization, intravenous acyclovir at 10 mg/kg every 8 hours is typically used^[15].

For shingles, antiviral therapy is most effective when started within 72 hours of rash onset^[9]. Treatment typically lasts 7 to 10 days or until lesions have crusted over^[15]. Studies show that antiviral medications decrease symptom duration and reduce the likelihood of developing postherpetic neuralgia, especially when started within 2 days of rash onset^[9].

For people with weakened immune systems, treatment is more intensive. Intravenous acyclovir is typically recommended initially, with a possible transition to oral therapy once clinical improvement occurs^[15]. Treatment duration is usually 7 to 10 days or until all lesions have crusted^[15].

Varicella zoster immune globulin (VariZIG) is a special treatment used for high-risk individuals who have been exposed to chickenpox or shingles^[9]. It should be given within 10 days of exposure, ideally within 4 days, to reduce the severity of infection^[9].

Prevention through vaccination

Vaccination is the most effective way to prevent varicella zoster virus infections^[1][12].

Before the chickenpox vaccine was introduced in 1995 in the United States, the disease was extremely common. In the early 1990s, more than 4 million people got chickenpox each year, with 10,500 to 13,000 hospitalizations and 100 to 150 deaths^[4][5]. Since the vaccination program began, chickenpox cases, hospitalizations, and deaths have decreased by more than 90%^[4][5].

Most people who are vaccinated will not get chickenpox. Those who do develop chickenpox after vaccination typically have a much milder form of the illness with fewer blisters and faster recovery^[7].

There is also a vaccine available to prevent shingles, which is recommended for older adults to reduce their risk of developing this painful condition^[8].

If you’ve been exposed to chickenpox or shingles and don’t have evidence of immunity, your healthcare provider may recommend post-exposure vaccination or other preventive measures depending on your risk factors^[17].