Chicken pox is one of the most infectious and important childhood diseases that all should be familiar with. It’s a viral infection that presents with a characteristic fever and rash, but it can have some severe and quite significant complications and there is a vaccine against it.
This important post is related to several other posts that I have published on this website, I suggest you refer to them, as needed, through the links attached here.
The story behind the name Chickenpox
The word “pox” means “spell” in Latin. In the past, diseases with skin manifestations were considered spells that had been cast upon people. What about the chicken part, you ask? There are several theories out there, the one I find most amusing is that the patient’s skin seems like a chicken picked on it.
What is Varicella – this is another name for the disease, and it comes from the word “Variola” – the name of the virus that causes Smallpox. Chickenpox used to be considered a milder version of Smallpox.
What causes chickenpox?
Chickenpox is a viral infection caused by a virus from the Herpes family, named Varicella-Zoster-Virus, or in short VZV.
Is the disease infectious and how is it transmitted?
You bet it is.
One can get infected through direct contact with blisters that contain the virus or through transmission in the air. That is why, prior to the vaccine era, families used to hold “infection parties” so that all the children would contract it and would attain natural immunity…. Only there could be complications, and they’re no fun.
The incubation period is between 10 to 21 days (14-16 days on average). Patients are most infectious on the first 1-2 days prior to the onset of rash (that is, the child can transmit the disease even before they know they have been infected themselves, and that is the main reason behind outbreaks), and up until all the skin lesions have dried up and covered with a crust.
It is important to note – household members that get infected from the first member to get ill will usually suffer a more severe disease, with more skin lesions and will have a higher risk of developing complications.
For example, if the first child to get sick got infected after having been exposed to a different child at daycare for a duration of 4 hours, he will suffer from the disease to a certain extent. When he/she transmits the infection to their sibling, their sibling’s symptoms will be more severe, after having been exposed to the first ill household member for a more significant length of time (exposure at home).
What are the signs and symptoms of chickenpox?
Just like in any viral illness, chickenpox usually begins with a generally ‘bad’ feeling, decreased well-being, fever, headache and abdominal pain. These may also continue into the rash phase, which characterizes the illness.
Next, the rash appears.
The rash may have several stages that develop quite rapidly. It starts in the area of the head and spread towards the trunk and limbs (though it involves the trunk more than the limbs). The rash comprises of flat, red lesions (macules) that evolve into raised lesions (papules). These then turn into blisters filled with clear fluid (vesicles), which then turn into pus-filled blisters (pustules). The lesions then finally form a crusted coat, dry up, fall off and heal. The rash is itchy. Occasionally, ulcers may appear in the oral cavity, the vagina and the conjunctiva of the eyes.
One of the most important characteristics of chickenpox is the presence of lesions at all stages of development in an affected child. That means, we may be able to see papules, blisters, pustules and scabs all at the same time in the same affected location. This only happens with chickenpox.
Children with skin diseases, such as atopic dermatitis (read more here), may have more severe and widespread illness.
In vaccinated children that were exposed to the virus and contracted it (usually after having received only one dose of the vaccine out of two), a milder, non-characteristic rash with only several lesions may appear.
What are the complications of chickenpox?
Lets just make this clear: most cases of chickenpox will resolve following several days of fever and rash, without causing any complications at all.
However, the complications that may occur (which are unpredictable), are what cause this common illness to be an important and dangerous one and the vaccine against it to be such an important vaccine. So, what are these complications?
A secondary bacterial infection in the lesion, due to itching and scarring.
Bacteremia – the transmission of bacteria from the secondary infection at the site of the lesion into the bloodstream.
Viral pneumonia with or without a secondary bacterial infection. This occurs more frequently in adolescents and adults that are unvaccinated.
Central nervous system complications – cerebellar infection, balance and gait abnormalities, infection of the brain and in very rare cases – stroke due to involvement of blood vessels in the brain.
Reduction in the number of platelets in the blood (thrombocytopenia). This is usually transient.
Other complications: kidney inflammation, liver inflammation, involvement of joints and more. The virus could theoretically (very rarely) cause inflammation in every organ in the body.
Who is at higher risk of developing complications?
Children who are immunodeficient, children with chronic skin conditions, chronic lung disease, secondary cases in household members, unvaccinated women (or those who had not been infected in the past) and their fetus (I will be discussing all of this under treatment).
How can chickenpox be diagnosed?
The diagnosis is usually made through observation and detection of the characteristic rash. When there is a history of exposure to a sick individual, making the diagnosis becomes even simpler. It is also possible to sample the fluid present in the blisters (or fluid elsewhere, for example cerebrospinal fluid) and test it using PCR testing for VZV (that same PCR test we all know so much about since the outbreak of COVID).
There are also tests that detect antibodies against VZV but we use those mainly to find out if someone was exposed to chickenpox in the past and has already developed antibodies.
How do you treat chickenpox?
The treatment can be divided into symptomatic (relief of symptoms) and medications against the virus itself.
This treatment is meant for everyone.
Paracetamol for fever. It is interesting that they advise against the use of Ibuprofen due to the increased risk of developing life-threatening infections from streptococcal disease (possibly because of concern that the primary signs of streptococcal infections may be masked with the use of such drugs). In children who receive Aspirin for one reason or another (or any other drug containing salicylates) – its use should be stopped if possible (not in those children receiving it as chronic medication, of-course) in order to prevent the development of the rare illness “Reye Syndrome” (a rare complication involving the liver and brain).
The trimming of nails is advised in order to prevent secondary infections transmitted through scratching.
Itch relief – frequent baths and use of Zinc oxide 5%. suspension (see here). Medications against pruritis can also be used (mostly first generation antihistamine drugs).
These include Acyclovir or Valacyclovir, administered orally to everyone except persons with immune deficiencies, who are treated with Acyclovir intravenously.
There is no need to treat regular cases of chickenpox since in most cases the medication is not very beneficial. The treatment is reserved for children who at risk of developing severe illness, these include:
Unvaccinated children over the age of 12.
Children with chronic skin conditions.
Children with chronic lung disease.
Children who are on long-term Aspirin treatment.
Children being treated with steroids.
Children with immunodeficiency.
Secondary cases in household members.
Unvaccinated, pregnant women – in order to reduce the rate of complications in the mother. There isn’t really much information about whether it reduces the risk of congenital infection in the fetus (see more about chickenpox and pregnancy below).
It is important to remember that there is a 72-hour window from onset of rash for treatment to be effective, since past the 72 hours the virus stops replicating and the medication becomes ineffective.
Is there a vaccine against chickenpox?
Yes. There is a live-attenuated vaccine. However, it is not part of the regular immunization schedule everywhere in the world. In countries that administer it as part of their immunization program, it is either given at the ages of 1 year and 3-4 years or 1 and 6 years. It can be administered together with the vaccines against Measles, Mumps and Rubella (MMRV), or on its own.
Both vaccines are very efficient. The two doses of vaccines provide excellent protection against the disease; over 90% protection against the clinical disease and almost full protection against a severe disease and its complications.
I know that many people say “Oh well, we all had chickenpox when we were little, it’s not such a horrible disease” but I really think that the vaccine is very important and it provides protection against both the discomfort of mild disease and the complications of a more severe disease.
What are the adverse effects of the chickenpox vaccine?
Firstly, I must state that this vaccine is very safe. Some of the adverse effects include redness, pain and swelling at the site of injection and fever between days 3-7 after the vaccine is administered. There is also an increased risk of febrile seizures (mostly when it is combined with MMR vaccine) and a rash that can occur anytime between the 5th day and up until the 42nd day after the vaccine is given. The rash usually includes several maculo-papular lesions but no vesicular lesions.
There is a small risk of transmitting the vaccine virus to individuals who have not been vaccinated if the person receiving the vaccine develops a rash. Therefore, if a person is at risk of developing serious illness (as I mentioned before), they should avoid direct contact with those who received the vaccine recently and have developed a rash. Otherwise, there is no need to separate household members who were just vaccinated.
Can a person who was vaccinated still transmit disease? Mostly those who have only received one dose of the vaccine. That’s also why we tend to see outbreaks and mild disease (low-grade fever and several non-classic lesions that may be difficult to identify) in toddlers who have not yet received their second dose.
If a child is infected with chickenpox after they’ve received their first dose, a second dose is unnecessary as he is now considered immune.
What about if the child gets it before they’re one year old (i.e before receiving their first dose of vaccine)? I suggest you consult with a vaccine specialist (clue from me: vaccinate them!)
Why is chickenpox dangerous for pregnant women who are unvaccinated or have never had chickenpox?
Chickenpox may lead to intrauterine death of the fetus or to developmental abnormalities, including abnormalities in development of the brain, eyes, limbs as well as scarring of the skin. It happens in unvaccinated women or those who had not been infected with chickenpox prior to pregnancy, if they get ill in their first or second trimester (mainly gestational weeks 8 to 20). Definitely not recommended.
In addition, if a pregnant woman gets ill 5 days prior to, or two days after delivery, she could transmit the infection to her newborn who may develop severe disease, since his immune system is still weak and underdeveloped and he will not yet have attained antibodies from his/her mother at this time.
How can an adult know if he has been vaccinated for chickenpox or has previously had the infection?
People who got vaccinated can find out through their vaccine records. Everyone else – ask your mothers. Research papers have shown that when a mother remembers that her child had chickenpox, she is usually right.
One can also get tested for the presence of VZV antibodies in their blood. The presence of IgG type antibodies suggests immunity as a result of previous infection or vaccination.
How are chickenpox and shingles related (Herpes Zoster)?
Just by looking at the names (VZV, varicella-zoster virus), one can tell that the virus that causes chickenpox is in fact the same virus that causes Herpes Zoster (Shingles). After primary infection with this virus and the development of chickenpox (and also after vaccination, even though it is much less common), the virus resides in the nuclei of the central system and remains dormant there for long periods of time. Sometimes, it is able to “wake up” and cause the rash characteristic to shingles – a very painful patch of blisters that appear over a red base and spread along the route innervated by the nerve on which the virus was dormant at for years.
Therefore, all those who are healthy and above the age of 50, or anyone who is above the age of 18 and suffer from a chronic illness – it is really important that you read about shingles and the vaccine against it, here.
So, what should I do if my child has chickenpox?
It’s very simple. Make sure your child stays at home. Do not send them to daycare or school, do not meet up with friends. Do not meet up with immune deficient people or pregnant women who have not been vaccinated or have never had chickenpox. Read the section about treatment above. And wait. If you notice any complication, see your family physician for a checkup.
You can return to regular daily activities and school only after a physician has approved of it and once new lesions have stopped appearing and all the old lesions have dried up and are covered with crust (this usually occurs 6 days after the onset of rash).
Very very important – if there is a household member who is unvaccinated or has never had chickenpox – go and have them vaccinated immediately (if there are no contraindications), preferably within 3-5 days after the exposure but also if it has been past 5 days. Vaccinations can certainly prevent severe disease and complications. This concept is referred to as ‘post exposure prophylaxis” and it’s very useful in chickenpox.
For children who end up receiving their first dose of vaccine prior to their one-year birthday – make sure they receive another dose at the age of 1 year.
What should be done if my child was exposed to chickenpox?
Firstly, try and understand where this exposure occurred. Considerable exposures are those that occur at home, at school or on a playdate etc.
If the child is fully vaccinated (i.e has received two doses of the vaccine or had the disease in the past) – you’re all set. There is no need to do anything.
If your child has not received his two doses yet – go and get him vaccinated within 3 to 5 days of exposure (if there are no contraindications).
For children who are immunodeficient, pregnant women who have never had chickenpox and for newborns – see your doctor and consult with them regarding the need for passive immunization (a dose of antibodies) as they are unable to receive the live-attenuated vaccine. The topic of active/passive immunization is beyond the scope of this post and in such cases it is best to refer to your primary care physician as soon as possible for a consult.
In very rare cases – anti-viral therapy is considered for children who have been exposed but have no yet developed infection.
What should be done if a pregnant woman was exposed to chickenpox?
Relax. Try to remember if the she has had chickenpox in the past or has been vaccinated. If the mother remembers her having had the infection or if there are records of immunization (with 2 doses) – she is safe, there is no need for any further workup or treatment.
If there is any doubt – she should get tested for antibodies so as to find out whether she is immune. If she does have antibodies in her blood – she is immune. If her bloodwork reveals no antibodies – she needs to receive passive immunization (antibodies) as soon as possible and no further than 10 days post exposure.
To summarize – chickenpox is an important childhood infection with complications that pediatricians may still run into from time to time.
At the current era, where a good, safe and efficient vaccine exists – it is important to ensure proper immunization so as to avoid redundant trouble.