Now we'll cover varicella.
Varicella, also called chickenpox, is a very contagious viral disease.
It is caused by the varicella-zoster virus.
This typically affects 2-8 year-olds but can affect anyone.
It's usually mild but can be serious and this causes itchy skin lesions that can scab and scar.
This is a vaccine-preventable disease.
The etiology. This is caused by the varicella-zoster virus or the VZV
and this is a double-stranded DNA virus that is part of the herpesvirus family.
It's the same virus responsible for shingles.
After someone has had chickenpox, the virus can stay dormant
or rest in the nervous system for the rest of their life and it can reactivate or wake up later as shingles.
This used to be very common in the United States prior to the vaccine.
There used to be 4 million cases per year, greater than 10,000 hospitalizations, and over a hundred deaths.
We know based on records that chickenpox dates back to early civilizations.
So it's transmitted in a highly communicable fashion.
Infection rates in non-protected patients is greater than 90% in close contacts.
The infectious particles are cell-free virus particles derived from two things:
skin lesions and the respiratory tract.
Now, the virus can be spread in two ways.
The first is droplet transmission and this is via coughing and sneezing
because remember, your patient is expelling these droplets even prior to the rash appearing.
The second is direct contact with blisters, saliva, or mucus of a person infected with chickenpox.
And then you'll touch their contaminated items such as their clothing.
If a person has never had chickenpox and they come in direct contact
with the blisters of a patient with shingles, the virus can spread
and lead to chickenpox in the patient who's never had chickenpox nor had the vaccine.
Now, you may have heard of pox parties and this is where a parent
invites the whole neighborhood over to see if they can get all the kids to have chickenpox
when one child has chickenpox.
Typically, they strip the kids down into their underwear
and they want them to touch each other's rash to try to get chickenpox
but what these parents need to remember is the kids can also acquire this via the droplets,
coughing, and sneezing. And these pox parties are not recommended.
So chickenpox is contagious from two days prior to the rash appearing until all of the blisters have crusted over.
And this is a problem because patients don't know they have chickenpox,
the parents don't know their child has chickenpox,
and they're still sending them to school and community activities.
So after a varicella-zoster infection, IgG and IgM,
and also IgA antibodies are gonna start to appear.
And this can be in the first 2-5 days after the rash and this will show highest levels at about 2-3 weeks.
The IgM antibody levels then rapidly decrease
and they typically can't be found after about a year after infection.
Although the IgG antibody level is going to decrease slowly over time,
the rate of which their protection wanes is different for everyone.
Remember, the IgG is the long-term immunity, the IgM is with the acute exposure.
Sometimes the IgG will wane and a patient will be susceptible again to the virus
and can actually get a second exposure but sometimes it confers a lifelong immunity.
You'll also develop cell-mediated immune responses that are gonna limit the scope of the infection.
So the pathology.
Varicella is gonna spread from the mucus and the skin lesions to the local sensory nerves.
Here, it will stay latent in the dorsal ganglion cells of the sensory nerves.
If the patient's re-exposed to this virus or in a stressful situation, this can reactivate
and result in herpes zoster which is shingles. Here you'll see the nerve fiber.
The dormant varicella-zoster virus is gonna stay here and at the right moment
when the immune system is weakened, it can awaken. It can travel up the nerve
and cause a burning pain and a sensation to develop on the skin.
I often have patients say,
'You know, it feels like there's a tag on my shirt that's rubbing my skin but there's not a tag there.'
They just get a sort of irritating feeling.
Next, puss-filled blisters are gonna appear on the skin
and these last about 3-5 days then these will form a scab and heal.
And remember, these shingles lesions stay only on half of the body.
Right, they don't cross the mid-line and they stay in one dermatomal tract
so this is very, very easy for the clinician to diagnose clinically.
The patient after having shingles can develop a postherpetic neuralgia
which is nerve damage caused by the virus
and this is gonna cause an intermittent or continuous nerve pain in the area affected by their shingles.
The patients have described pain as burning, stabbing, shooting, throbbing,
or sometimes even like electrical shocks.