Kid's Health topics

Chicken Pox (Varicella)

I am a child of the early 80s (shh don’t tell anyone), and like many people of that generation and earlier, I have vivid memories of chickenpox sweeping through my family and wreaking havoc. I have a very large family and we actually had 2 waves of it come through as the family grew. Being only the second child (of 8), I was in the first wave, and though I was a child of only 2 or 3 at the time I can still remember the rampant itch which led my mother to tie fingerless woollen mittens onto my hands so tightly I couldn’t get them off to scratch, and I still abhor the smell of the Pinetarsal bath oil added to every bath to try to soothe my inflamed skin. When I was a teenager, the second wave went through and hit the remaining 5 or so siblings who had not yet been exposed. The first we knew of its presence was when we ‘lost’ my sister at Underwater World on the Sunshine Coast during a family holiday. We all spent a good hour searching for her with the help of the staff, getting more and more frantic as time went on. Turns out she had crawled under one of the racks of clothes in the gift shop when we were milling around and gone to sleep with a 40 degree temperature that had just come on. A few days later she was covered in spots from head to toe, and of course it spread through all the younger children like wildfire over the following weeks. Though all my siblings thankfully recovered well, I remember them being just so miserable and unwell at the time, and some of them still bear the scars of the rampant pustules that covered them.
Thankfully this is a scourge that most children these days will never experience, and the few that do are unlikely to experience it in the same way as the children of my generation. Why is this, you might ask? The answer is vaccination, with a government funded vaccine introduced in Australia almost 15 years ago now. This has dramatically reduced the incidence of chicken pox such that many children will never experience the natural illness in their lifetime. Despite this however there are still small outbreaks of the illness reported each year, usually centred around schools or daycare centres, so it has unfortunately not disappeared entirely yet.

So what do I need to know about chickenpox?

Chickenpox is cause by the Varicella Zoster Virus (VZV), one of the members of the Herpes virus family. It has an incubation period of up to 21 days after infection, which means that your child could develop symptoms of chickenpox anywhere from 1-3 weeks after coming into contact with the virus. The ‘wild-type’ or ‘natural’ virus is highly contagious and is spread from person to person most commonly through aerosolized droplet spread ie. through coughing or sneezing virus into the air allowing it to be breathed in and enter through the lungs of the next child. You can also spread the infection through contact with the fluid inside the pustules. The difficulty in controlling the spread of chickenpox is that the most contagious period occurs in the few days before the characteristic rash appears, so usually by the time it becomes clear you are dealing with chickenpox, your child may already have infected several other children, though this may not become apparent for several weeks.
The infection usually begins with typical viral symptoms such as fever, headache, runny nose, and cough. Some children are really quite unwell in this period. Approximately 1-2 days after these symptoms start, the rash appears. This rash often starts as small red spots and progresses to pus filled lesions or blisters, which are extremely itchy. These lesions usually pop up in ‘crops’ with several lesions clustered together erupting at around the same time. The lesions can occur anywhere on the body, though seem to have a preference for the head and neck, shoulders and arms. Blisters around the ears and even inside the ear canal are fairly characteristic of chickenpox. The blisters last for around 3-5 days before they dry up and crust over. Once all lesions are dry and crusted the child is no longer infectious to others.
So what is the big deal, we all had it and survived, right?
Well firstly, wrong. Though many people did manage to get though this illness without any permanent damage, chickenpox can be a very serious illness in some people. Complications of chickenpox can include cellulitis (spreading bacterial infection), pneumonia and encephalitis (infection in the brain), and the pre-vaccine the death rate from Chickenpox infection was about 3 in every 100 000 cases in developed countries. Though not sounding like a lot, this was estimated to equate worldwide to 4.2 million complications leading to hospitalisation and 4200 deaths annually (WHO position paper, 2014).
People whose immune system is not working as well as it should, for example from chronic illness, chemotherapy, the very young or the very old are more vulnerable to infection and more susceptible to these severe complications. Pregnant women are also vulnerable to infection and complications of infection if not already immune, and infection at certain stages of pregnancy can have significant consequences to both mother and baby.
Even without taking into account these very serious but thankfully rare complications, chickenpox itself can be a nasty illness, with more severe illness generally seen in older children or adults than in younger children. The economic and social cost of time off daycare and school, and thus time off work for parents is pretty high for a disease so common.
Also, after the initial infection the varicella virus lays dormant in the body for many years and in quite a number of people will reactivate, usually in times of stress, as shingles. Those of you who have experienced shingles will know the pain that can be associated with this condition, which in some people can persist long after the infection has gone again.

So why do we still have chickenpox if most people are vaccinated now?

Well there are several reasons for this. One is that the vaccination is not 100% effective. In fact a single vaccine is only estimated to be about 80-85% effective for preventing varicella (though up to 95-98% effective at preventing the severe form of the illness) compared to up to 98% effective after 2 vaccinations (Australian Immunisation Handbook 10th edition, 2018) which are in fact recommended for all children, though the National Immunisation Program only supplies a single funded vaccine.
Another reason is that the rates of immunisation have dropped over the years, leaving pockets of vulnerable children who can more easily contract and spread chickenpox. Adding to this are a number of children who are unable to be vaccinated for medical reasons, for example due to treatment for cancer, autoimmune conditions, or previous severe allergic reactions to vaccine components etc.
Another reason is because humans will always be a reservoir for the chicken pox virus, given the fact that it remains dormant in or bodies for life occasionally presenting again as shingles. This can occur even if your only contact with chicken pox has been the vaccine, though shingles in vaccinated individuals is far less common than in people who have experienced the natural infection. It is possible to then to spread chicken pox to others from shingles through direct contact with the fluid in the blisters.

So how can I protect my child against chicken pox?

The key is vaccination. If your child is over 18 months and vaccinated via the National Immunisation Program, they will have received a single dose of varicella containing vaccine already. If they are over 12 months but under 18 months, you can elect to give them an early varicella vaccine, though this would not be covered by the government funded program, and would still need to be repeated at 18 months. This does have the benefit however of giving them the recommended 2 doses of vaccine to give maximum protection. For children who have only had a single dose, it is recommended to have second for best protection.

What do I do if my child has been exposed to chicken pox, or I am worried they may have it?
Daycare centres and schools will often notify parents of confirmed cases of chicken pox when they occur. If you are concerned about an exposure your child may have had it is worth a chat to your GP, as there are different levels of exposure and risk depending on the individual circumstances and health and vaccination status of your child. It is possible to give a ‘post exposure’ vaccination that may help prevent your child contracting chicken pox after an exposure, but the details of this are best discussed with your doctor. Immunocompromised children who have a significant exposure may be at real risk of serious infection so if this is your child, please discuss it with your child’s regular doctor as soon as possible to determine the next steps.
If you are concerned your child may have chicken pox then the first step is to visit your GP, though it is very important to alert the reception staff of your concerns when booking the appointment so your child can be appropriately isolated and avoid spreading to others in the waiting room. Swabs can usually be done to confirm the diagnosis and your GP will discuss with you how best to manage and isolate your child as well as the risk to any other family members.

 

Well that’s all folks!

Til we meet again,

Katie

References and further information:

Australian Institute of health and Welfare, 2018. Vaccine Preventable diseases fact sheet series: Chicken Pox in Australia. https://www.aihw.gov.au/getmedia/30dc6fcd-352f-41b9-9e2f-4b4055630f39/aihw-phe-236_Chickenpox.pdf.aspx
Australian Technical Advisory Group on Immunisation (ATAGI). Australian Immunisation Handbook, Australian Government Department of Health, Canberra, 2018, https://www.immunisationhandbook.health.gov.au
Immunise Australia http://www.immunise.health.gov.au/
World Health Organisation, 2014, Weekly Epidemiological Record. Varicella and Herpes Zoster Vaccines; WHO position paper, June 2014. No 25.89. https://www.who.int/wer/2014/wer8925.pdf?ua=1

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