How Chicken Pox Works

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.