What is chickenpox?

Chickenpox is a highly contagious infection caused by the varicella-zoster virus (VZV), the virus also associated with shingles. Most people can recognize chickenpox by its characteristic itchy, blistering rash and red bumps (papules, sometimes called “pox”). The majority of children born today are vaccinated against chickenpox. Before the introduction of the vaccine, however, chickenpox was a rampant childhood disease: nearly all people born in the United States before 1980^[1] had chickenpox as children.Chickenpox is contracted through person-to-person contact. Those who have already had the disease are considered to have developed immunity to it, meaning they cannot get the infection again. However, having chickenpox as a child means there is a chance you may develop shingles, another infection caused by varicella zoster, as an adult.

How common is chickenpox?

Chickenpox is not nearly as common as it once was in the United States. Since the addition of the chickenpox vaccine to the childhood vaccination schedule in 1995^[2], the incidence rate of chickenpox dropped dramatically. It is estimated that in the United States alone, 3.5 million cases of chickenpox and 100 deaths resulting from complications are prevented^[3] by the chickenpox vaccination each year.

What causes chickenpox?

Chickenpox is an infection caused by the varicella-zoster virus (VZV). It is highly contagious to those who have not previously had chickenpox or received the vaccination. Chickenpox is contracted by coming into direct physical contact with the rashes or sores of someone with an active chickenpox rash. As with other viral infections, you can also contract chickenpox from breathing in the droplets from a cough or sneeze of someone infected with the disease.

Risk factors for chickenpox

Certain factors may increase your risk of developing chickenpox. These risk factors^[4] primarily relate to your prior vaccination status and the health of your immune system. One of the biggest factors that increase the risk of being infected with chickenpox is lacking immunity to the disease. If you have not been vaccinated against chickenpox (either as a child or as an adult) or had the disease as a child, you’re much more likely to develop it as a result of coming into contact with an infected person. People who are immunocompromised (have weakened immune systems) and do not have immunity to chickenpox are also at an increased risk for developing severe cases of chickenpox^[5]. This population includes people taking immune-suppressing medications (such as steroids or chemotherapy), people with leukemia or lymphoma, newborn babies whose mothers got chickenpox around the time of delivery, pregnant women, and prematurely born babies.

Chickenpox symptoms

The most recognizable symptom of chickenpox is its characteristic red, itchy rash. However, other signs and symptoms^[6] may arise one or two days prior to the development of this rash, including:

• Fever
• Fatigue
• Sore throat
• Loss of appetite
• Rash (small, itchy blisters)
• Scabs (once the blisters burst and dry out)

Chickenpox rash

The chickenpox rash appears between 10 and 21 days following exposure to the virus and usually lasts for five to 10 days^[7]. This rash appears as small, red blisters, typically found on the trunk (chest and back), face, arms, and legs. Once the chickenpox rash forms, it progresses through three phases:

• Raised red or pink bumps, called papules, break out over the course of several days
• Small fluid-filled blisters, called vesicles, develop in roughly one day, then burst open and leak
• Broken blisters begin to crust and scab over (usually about six to seven days after the formation of initial papules)

It is not uncommon for new bumps to continue forming for up to four days after the first blisters appear. Because of this, you may have all three stages of the chickenpox rash (papules, blisters, and scabbed lesions) at once. It can take up to two weeks for scabbed-over blisters to fall off completely. Some people notice pockmarks or scarring where these scabs fell off. It’s important to remain at home while experiencing any of the symptoms of chickenpox, as the virus can be contagious for up to two days before the appearance of the rash and remain contagious until all broken blisters have scabbed over.

Complications from chickenpox

While chickenpox typically resolves on its own and doesn’t usually cause any lasting damage beyond minor scarring, some severe cases of chickenpox can lead to further problems. Possible complications^[8] of chickenpox include:

• Shingles: Both shingles and varicella are caused by the varicella-zoster virus. If you ever had chickenpox as a child (or, less commonly, if you received the chickenpox vaccine), the virus could come out of its latent stage and cause shingles as an adult.
• Bacterial infection: In some cases of chickenpox, the papules that form may not blister and scab over, instead becoming red, warm to the touch, and even more tender. This could be a sign of infection, which may become life-threatening if the infection were to travel to the bloodstream (a condition known as sepsis).
• Hepatitis: Infection caused by the varicella-zoster virus has been associated with hepatitis (liver inflammation), typically in people who are immunosuppressed^[9] (such as patients with AIDS or those who have received organ transplants).
• Pneumonia: About 5–15% of adults with chickenpox will develop a lung illness as a result of the varicella zoster virus. If you are pregnant, smoke cigarettes or tobacco, have chronic obstructive pulmonary disease (COPD), or have a suppressed immune system, you are at an increased risk of developing chickenpox-associated pneumonia^[10].
• Toxic shock syndrome (TSS): TSS is a condition caused by infection with either the Staphylococcus or Streptococcus strains of bacteria. TSS has been known to occur in children^[11] with chickenpox.
• Brain inflammation: Inflammation of the brain (known as encephalitis^[12]) has been associated with chickenpox.
• Dehydration: Symptoms of chickenpox can include fever and fatigue. If these symptoms are extremely severe, they can cause a person to become dehydrated^[13]. In some cases, hospitalization may be required.
• Reye’s syndrome: Reye’s syndrome^[14] is a condition that affects the brain and liver, causing swelling. It most commonly affects children or adolescents recovering from viral infections, such as chickenpox or influenza (the flu).
• Death: In rare cases, complications like blood infection may lead to death⁷. Thankfully, deaths from chickenpox have declined significantly due to widespread vaccination against the disease.