Chickenpox is a very, very contagious disease that you’ve almost certainly either heard
about or experienced yourself.
The virus that causes chickenpox is called Varicella-Zoster Virus, which is why chickenpox
is sometimes referred to as varicella.
This virus is also part of the human herpesvirus family.
Varicella is one of the five classic childhood diseases, along with rubella, roseola, fifth
disease, and measles.
Virus-wise, VZV shares a lot of characteristics with the virus we covered in the previous
tutorial, Herpes Simplex Virus.
Like HSV, Varicella-Zoster Virus is able to establish a latent infection of neurons and
cause recurrent disease.
When that happens, it’s called herpes zoster, though the name for this that you’ve probably
heard is shingles.
Other similarities between VZV and HSV involve cell-mediated immunity, and the characteristic
lesions that look a little bit like blisters.
One thing that sets the viruses apart, though, is that VZV is spread by the respiratory route.
Once a local infection is set up in the respiratory tract, the virus is spread through the blood,
which leads to those characteristic skin lesions all over the body.
Compared to other human herpesviruses, VZV has a smaller genome.
VZV also replicates a little bit more slowly, and infects fewer types of cells than HSV.
Once the virus is inhaled, it sets up shop in the lungs, with a primary infection beginning
in the mucosa of the respiratory tract.
Similar to HSV, infection goes through a fairly complex step-wise process.
After the virus replicates in the lungs, it spreads through the bloodstream and lymphatic
system, and then spreads throughout the body and to the skin.
The virus causes a real bummer of a rash, and someone infected with chickenpox may develop
as many as 500 itchy blisters.
They may or may not develop a fever, headache, and fatigue as well.
The virus can be spread through direct contact or the tiny droplets that get into the air
when someone who has chickenpox breathes or talks, and this can happen anywhere from 1
to 2 days before the infected person gets a rash, all the way until their blisters have
formed scabs.
That’s a fairly large window of transmission.
Once your body has cleared the infection, the virus lays dormant in your nerve cells.
Reactivation of the virus, which would again be called shingles, is most common in older
adults, or in immunocompromised individuals.
When that happens, the virus replicates and releases copies of itself all along the neural
pathway to infect the skin, causing a rash.
Shingles can be incredibly painful, and in some cases, someone with shingles may develop
a complication that causes chronic pain for months or even years.
When it comes to treatment, children with varicella typically just ride out the duration
of the disease.
For adults or immunocompromised people, there are several antiviral treatments that are
FDA-approved to treat infection.
However, much higher doses of these antivirals are needed to treat VZV in comparison to HSV.
Thinking about prevention, there are several highly effective vaccinations out there that
create immunity to VZV, both for children and adults.
And with that, we’ve covered a couple of the most common human herpesviruses, so let’s
move on to a few more members of the group.