How Chicken Pox Works


That's not a bad case of back acne. It's chicken pox.
That's not a bad case of back acne. It's chicken pox.
David Tomlinson/Getty Images

Despite differing languages, cultures and upbringings, kids across the world once shared the same itchy, icky, blistery milestone: chicken pox. From Beijing to Boston, these pesky pustules have plagued up to 95 percent of children and adults in densely populated areas, according to the Public Health Agency of Canada. Sprouting anywhere from 30 to 1,500 blisters on its victims, this globetrotting nuisance leaves people feverish and aching to scratch.

Chicken pox is the common name for the varicella zoster virus, which has harassed humans for centuries. Naples-born Giovanni Filippo Ingrassia, who studied the structure of bones, first identified the varicella virus in the 16th century [source: Ackernecht]. It took another few hundred years before doctors could consistently tell chicken pox apart from smallpox, its more lethal viral cousin [source: Centers for Disease Control and Prevention (CDC)].

The varicella virus is incredibly contagious, spreading nimbly through the air between unsuspecting targets. How contagious? Some doctors say that you can catch chicken pox from a shopper parked in a different aisle of the supermarket [source: Rauch]. It typically strikes children under 10 years old during the winter and early spring [source: CDC]. Consequently, most kids in the U.S. are now vaccinated for it, drastically reducing the number of people infected.

In this article, we are going to learn why chicken pox is so prevalent, what it does to your body, how to treat it and how to avoid it.

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What is the chicken pox virus?

The airborne varicella virus enters the body, then infects the non-immune person.
The airborne varicella virus enters the body, then infects the non-immune person.
HowStuffWorks 2008

We know what a pox is -- a viral infection that produces widespread blisters that can erupt. What isn't clear is how the "chicken" got connected with the "pox." The Oxford English Dictionary attributes the "chicken" to the non-threatening nature of the pox. In other words, that pox was cowardly (or chicken). Other people have guessed that the "chicken" stems from the blisters' resemblance to chickpeas or, less charitably, to the fact that an infected person looks like he or she has been pecked over by a chicken.

Now that we've explored its name, let's examine its life. Viruses are incredibly small particles (about one-millionth of an inch) that must attach to host cells to live and reproduce. Viruses enter our bodies through our nose or mouth or through broken skin. The varicella virus also likes to sneak in through the mucous membranes lining the eyelids and eyeballs.

Once in, the varicella virus latches on to host cells in the nose and surrounding lymph nodes and reproduces like mad. The replicated varicella particles then travel to the liver, spleen and sensory nerve tissues. After another round of viral reproduction, the particles infect the skin cells. This skin infection prompts the telltale chicken pox rash.

Varicella zoster virus replicates and causes chicken pox.
Georgia Musil/Getty Images

Until the rash appears, people usually don't know that the varicella virus has been incubating in their body for 10 to 21 days. The incubation period refers to the time that elapses between when you get infected and when you start to show signs of being sick. People with chicken pox become contagious during the last one or two days of this period, right before the rash breaks out. This incubation period makes chicken pox highly contagious; people usually don't even know they have it until after they've spread it. Nine out of 10 non-immune people who live with someone with the varicella virus will catch it [source: CDC].

The varicella virus can move from your bloodstream to someone else's in several ways. A simple cough or sneeze from an infected person can expel airborne virus particles to be unknowingly inhaled, or tiny droplets of liquid inside the blisters can be released into the air. Physical contact with the rash before the blisters have dried also can spread the virus to someone else.

Now that we know how the body reacts to the virus on the inside, read on to find out why chicken pox makes your skin look like a connect-the-dots puzzle.

Chicken Pox Symptoms

The pesky pustules fill with fluid then scab over.
The pesky pustules fill with fluid then scab over.
Dr. Kenneth Greer/Getty Images

Once the replicated varicella virus gets into your bloodstream, your immune system recognizes the foreign invader and begins fighting it off after the incubation period. You feel that fight in the form of a fever, which lasts about two or three days. Fever often precedes adult cases of chicken pox, while children break out with the blistery rash first.

The blisters, or vesicles, are membranous sacs filled with clear liquid. They form on small red spots on the skin about one to four millimeters across [source: CDC]. The fluid inside the vesicles contains a chemical that stimulates the nerve cells at the skin. The nerves then alert the brain that the body itches. Although unpleasant, itching is actually a positive sign that the body is working to ward off the virus [source: Nemours Foundation]. Three or four days later, the itching typically subsides, and the blisters soon burst or darken and scab over.

The number and location of the vesicles can depend on age, skin condition and vaccination status. In general, the rash begins on the scalp, face and abdominal regions. From there, anywhere from 250 to 500 blisters will spread across the average unvaccinated person and may appear in the eyelids, mouth and genitals. When chicken pox strikes someone in spite of vaccination -- referred to as a breakthrough case -- it ordinarily results in 50 or so blisters.

After about a week, the blisters scab and dry out, and the virus is no longer contagious. Until then, patients should quarantine themselves at the first outbreak to avoid passing the virus to others. As the physical symptoms disappear, the virus deactivates but remains in the body in the nerve cells. Later in life, varicella may reactivate with stress or age as the herpes zoster virus, or shingles, which we'll discuss in the Shingles section.

This timeline of the varicella virus, from initial infection to inactivation, outlines what happens when you get chicken pox:

The stages of chicken pox, from virus to dormancy
HowStuffWorks 2008

Rarely, a case of chicken pox develops into other, more serious illnesses and possibly death. In the next section, we'll discuss these complications and who should be concerned.

Chicken Pox Complications

Chicken pox can be a menacing foe. Before routine vaccinations, nearly 10,600 Americans were hospitalized for varicella-related causes annually, and more than 100 people died each year from it [source: Centers for Disease Control and Prevention (CDC)]. Sometimes, however, chicken pox isn't the only illness the body must fight. The disease can cause a broad range of related health problems, or complications, particularly when the virus travels to and infects other parts of the body.

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Mouse over the chicken pox complications to see how they affect ­the body­.

In most cases, people can treat chicken pox at home, as it works its way through the body in about a week. According to the Mayo Clinic, the following physical signs indicate that you should go to the doctor:

  • Fever lasting longer than four days or exceeding 102 degrees Fahrenheit
  • Rash spreads to your eyeballs
  • Rash appears infected
  • Dizziness
  • Tremors
  • Stiff neck
  • Increased vomiting or coughing

Although children make up a majority of chicken pox cases, they typically experience the fewest severe complications. However, kids need to be careful not to scratch the itchy blisters because about one in 20 children will get an infected rash [source: National Network for Immunization Information]. The bacteria from fingernails can infect the open blisters and cause a secondary infection.

The severe complications pose a greater threat to certain groups of people, which we will discuss in the next section.

Chicken Pox Risk Groups

A toddler with chicken pox. Children are most likely to give themselves a secondary bacterial infection by scratching.
A toddler with chicken pox. Children are most likely to give themselves a secondary bacterial infection by scratching.
Christopher Bissell/Getty Images

Although most cases of chicken pox will come and go in about a week, the following people should watch out for virus-related complications, according to the Mayo Clinic:

  • Infants younger than 1 year
  • People older than 15
  • Pregnant women
  • People with have a weak immune systems, such as cancer patients
  • People taking steroids to treat another disease, such as asthma

Babies younger than one year are particularly vulnerable to complications because they cannot receive the varicella vaccination, and their bodies may not have developed all of the antibodies, or specialized proteins, necessary to fight off the virus. Babies are born with some natural antibodies from their mother, but they only last from one month to a year. A mother who hasn't had chicken pox increases the chance for a severe outbreak because she does not pass along the virus-specific antibodies to her baby [source: Rauch]. 

Adolescents and adults make up only 5 percent of all varicella patients; however, they account for 35 percent of virus-related fatalities [source: CDC]. The older our bodies, the weaker our immune systems become, and the higher the likelihood of dangerous diseases developing from common infections, like varicella.

Routine chicken pox vaccination can avert potential chicken pox cases and reduce the chances of complications. In the next section, we'll learn about the varicella vaccine, who should get it and when.

The Varicella Vaccine: Preventing the Pox

Most American children must receive the varicella vaccination before entering school.
Most American children must receive the varicella vaccination before entering school.
Wide Group/Getty Images

Vaccines are like personal trainers for our immune system. They strengthen the body's ability to successfully combat specific diseases by stimulating antibodies, or proteins that fight off infections. After the Food and Drug Administration officially licensed the varicella vaccine (Varivax) in 1995, the number of reported cases of chicken pox dropped by 53 percent to 88 percent nationwide [source: Centers for Disease Control and Prevention (CDC)]. As of the 2015-16 school year, all states but Montana required the varicella vaccination upon entering elementary school [source: Immunization Action Coalition]. Some states also accept proof of prior immunization in the form of a medical record confirming that the child previously had chicken pox [source: CDC].

Because people can catch chicken pox following one dose of varicella vaccine, called a breakthrough case, the Advisory Committee on Immunization Practices (ACIP) recommends getting a second dose, sometimes called a booster shot. With the two doses, only one out of 10 people will experience a breakthrough case. When that happens, symptoms are generally lighter, with an average of 50 blisters [source: CDC].

After you catch chicken pox, you become immune to it, so there's no need for vaccination. However, the CDC has outlined specific groups of non-immune people who should and should not get vaccinated.

People who should receive the vaccine:

  • Healthy people one year old and above
  • Women considering pregnancy
  • People living with immunocompromised individuals

People who should not receive the vaccine:

  • Pregnant women
  • Babies under one year old
  • Cancer, leukemia and HIV patients
  • People prescribed high doses of steroids, such as asthma patients
  • People severely allergic to any ingredients in the vaccine, including gelatin
  • People who have received blood products during the past 3-11 months, depending on dosage
  • People with a family history of congenital hereditary immunodeficiency

An alternative treatment has been developed for people who are exposed to varicella but cannot be vaccinated. Although it's expensive, varicella zoster immune globulin (VZIG) can protect patients from the virus up to 96 hours after the initial exposure.

Some risk factors are associated with the varicella vaccine, according to the CDC, including discomfort at the injection site, rash, fever and seizure. Some people also think that vaccines can have more debilitating effects on children, such as autism. However, no reputable study has established a link between vaccines and autism. To learn more about these assertions and their accuracy, read How Vaccines Work.

Since most chicken pox outbreaks do not require a visit to the doctor, we'll tell you what you can do at home to soothe your discomfort. We'll get down to the nitty-gritty of oatmeal baths and the rosy relief of calamine lotion next.

Chicken Pox Treatments: Scratching the Itch

Oatmeal baths can soothe itchy chicken pox blisters.
Oatmeal baths can soothe itchy chicken pox blisters.
LifeStock

Like the common cold, there's no quick fix for chicken pox. But there are some options for easing your itch and reducing any fever or pain. First, clip your fingernails to avoid scratching and to prevent secondary skin infections. Also consider wearing gloves when you go to bed so you don't scratch in your sleep.

Second, soak in an oatmeal bath, one of the most popular at-home solutions for relieving itchiness. This oatmeal isn't the kind you eat for breakfast, rather it's a finely ground type called colloidal oatmeal. You can either buy a pre-prepared soak at the drugstore or make your own by grinding uncooked oatmeal in a blender and putting two cups in a warm bath.

People have used oatmeal as a skin treatment for centuries because its of unique chemical anatomy, which packs a three-in-one punch. Its water-absorbent starches provide the moisturizing power. Acidic compounds called phenols have antioxidant and anti-inflammatory properties. It also contains saponins, which are sugar derivatives found in soaps and detergents with cleansing and foaming capabilities.

Third, when you hop out of the tub, apply calamine lotion to your blisters to tackle the itch. Calamine is a pink zinc compound with anti-inflammatory properties that aid with drying the liquid inside the pox.

Fourth, over-the-counter pain relievers can help break your fever, but only use non-aspirin ones such as acetaminophen. Taking aspirin while battling chicken pox has been linked to Reye syndrome, particularly in children and youth. The syndrome is a rare, non-contagious condition that occurs in about one in a million cases [source: Nemours Foundation]. The prescription medications for varicella virus we discussed earlier are commonly reserved for individuals in danger of severe complications. For more information on how to safely treat your chicken pox, read Shingles and Chicken Pox In-Depth.

Once you heal from chicken pox, the good news is you're no longer itching and covered in blisters. The bad news is the varicella virus remains in your sensory nerve cells and can make a surprise visit in the form of shingles later in life. In the next section, we'll find out what happens when the virus comes knocking at your door for round two.

Shingles: Chicken Pox Part Two

The varicella virus can strike again after chicken pox in the form of shingles.
The varicella virus can strike again after chicken pox in the form of shingles.

After a case of chicken pox, the varicella virus remains latent in the nerve cells. Later, it can reactivate in the form of the herpes zoster virus, or shingles. Latency is a behavior specific to the herpes family of viruses that's basically like viral hibernation. Once you catch chicken pox and your immune system attacks it, the virus retreats to the nerve cells where it can remain inactive. Doctors aren't completely sure why and how the varicella virus moves from the nerves back to the skin and erupts into shingles, but there are factors associated with it, such as stress, age, illness, medication and, of course, touching the rash of someone with shingles [source: Mayo Clinic].

Although shingles can strike younger people, adults 50 years old and above are the most vulnerable to the infection. In fact, half of the unvaccinated people who live to be 85 years old will experience shingles, according to the Centers for Disease Control and Prevention. Overall, one million people come down with it yearly.

Shingles symptoms include:

  • Pain
  • Itching
  • Tingling rash area
  • Fever
  • Headache
  • Chills
  • Nausea

Shingles starts off as a facial or bodily rash with three to five days of blistering and scabbing. After two to four weeks, the rash clears. Medications including acyclovir (Zovirax), valacyclovir (Valtrex), and famciclovir (Famvir) can treat it. For more information on alternative treatments, read 10 Home Remedies for Shingles.

When herpes zoster attacks the nerve cells, it can damage them, causing pain in the rash area that can linger years after the physical evidence disappears. This condition is called post herpetic neuralgia. One in five shingles patients will experience post herpetic neuralgia, and the likelihood of it increases with age. There is no specific cure for the condition, but early medical care for shingles may reduce your chances of suffering from it [source: Mayo Clinic].

Rare shingles complications include:

  • Pneumonia
  • Hearing and vision problems
  • Encephalitis
  • Death

The Food and Drug Administration approved a shingles vaccine in 2006 for people over 60. The vaccine is a more potent version of the varicella vaccine. A clinical trial showed a 51 percent efficacy rate in preventing herpes zoster and reducing symptom severity. Sixty-six percent of the participants also did not experience any post herpetic neuralgia [source: CDC]. The most common side effect reported from the herpes zoster vaccine shot was soreness in the injection area. In addition, people vaccinated for chicken pox are less likely to develop shingles. Conclusive data for how well it protects someone against shingles is still being researched [source: National Institute of Neurological Disorders and Stroke].

To learn more about how our bodies react to disease, explore the links on the next page.

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Sources

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