Authors: Debora Freitas / Editor: Nikki Abela / Codes: / Published: 13/12/2022
The case: A 6-year-old Ellie came to A&E 7 days after her chickenpox started. She was miserable, still spiking a fever, and had erythema spreading over her abdomen and leg. Her mum said she was increasingly lethargic over the last 2 days.
She was treated for dehydration and suspected septicaemia with IV fluids, broad spectrum antibiotics and acyclovir. Blood cultures later grew Group A Streptococci. Following further deterioration she later needed to be transferred to PICU for stabilisation and taken to theatre for debridement for necrotising cellulitis.
Introduction: Chickenpox is a highly infectious viral infection that is commoner in children and typically presents with fever, myalgia and a typical itchy rash, which begins as small red bumps before turning into blisters over 3-5 days. The blisters dry over the week and scabs form which eventually fall off. Caused by the varicella-zoster virus, it spreads from patient to patient through droplets or direct contact, and unless vaccinated or previously infected, almost any contact will lead to infection.
Chickenpox mostly affects school aged children between the age of 2-10 and whilst vaccinations are not a part of the routine childhood schedule, they are available privately (sometimes even via your GP) and can be offered for free to people in close contact with people vulnerable to the virus (such as those with immunodeficiency) [1]. Whilst treatment for the most part is entirely symptomatic, including topical agents to relieve pruritis, and paracetamol for myalgia and fever antiviral drugs can be used when there is greater risk of complications. In this blog we will review severe complications of chickenpox that can lead to hospitalisation.
Prevalence of chickenpox complications: Annual surveillance data suggest that over a year 112 cases of severe complications from varicella were admitted to hospital in the UK and Ireland. The causes are summarised in Table 1 (adapted from Cameron et al.) [2]. Of these 112 cases, a quarter required ITU/HDU admission and 5% died. So while complications are rare, the consequences can be severe.
Table1: Frequency of severe varicella complications over 12 months
| Pneumonia | 30 |
| Bacteraemia/septic shock | 30 |
| Encephalitis | 26 |
| Ataxia | 25 |
| Toxic shock syndrome | 14 |
| Necrotising fasciitis | 7 |
| Purpura fulminans | 5 |
| Fulminant varicella | 5 |
| Neonatal varicella (perinatal infection) | 3 |
Chickenpox in neonates: There are inconsistencies in how newborns are managed following exposure to varicella. However, varicella infections in the neonatal period can have severe consequences particularly if the newborn does not have maternal antibodies against varicella. Maternal infection during the first two trimesters can lead to congenital varicella which carries a 30% mortality rate during the first month of life [3]. Transmission of chickenpox from mother to child can occur transplacentally, through direct contamination during delivery, or through post-natal infection by respiratory droplets or direct contact with lesions.
The highest risk period is immediately around delivery up to 2 days of age as the newborn will have had limited time to acquire maternal protective antibodies. Mortality rates are suggested to be as much as 20% during this time however the administration of varicella-zoster virus immunoglobulins has significantly reduced this. It is important when reviewing such cases to remember the long incubation period chickenpox has (10-23 days) when attempting to determine the approximate time of infection. Table 2 (adapted from Blumental et al [3]) highlight the association between timing of maternal infection and the clinical presentation.
Table2: Association between timing of maternal infection and the clinical presentation
| Clinical presentation of mother and child according totiming of chicken pox infection | |
| Timing of maternal infection | Clinical presentation |
| Week 1-20 of gestation | Congenital varicella in 2% of cases (characterised by skin, eye, bone and CNS lesions) on the growing fetus). 20-30% mortality. |
| Third trimester | Maternal pneumonia in 10-20% of cases 10% mortality |
| Around delivery 5-6 days before<4 days before to 2 days after | Neonatal varicella in 20-50% Mortality 0%Mortality 3-20% |
Management of Chickenpox: While most children with varicella infection do not require antiviral treatment, treatment is recommended in the following circumstances:
- Any child with a primary immune deficiency
- Any child on immunosuppressive medication (during and up to 6 months after chemotherapy) or replacement steroids
- Neonates under 4 weeks of age
- Children with severe varicella complication (Table 1)
Early intervention with immunoglobulin (IVIG) therapy is essential along with intravenous acyclovir particularly in septic children. Whilst IVIG is effective up to 10 days after exposure, it should ideally be given within 7 days. Treatment with IVIG is recommended in the following circumstances:
- Those in whom antiviral treatment is recommended
- Babies born to mothers who develop chickenpox in the 7 days before and after delivery
- Neonates <7 days of age exposed to chicken pox who have no varicella zoster antibodies (i.e. if the mother has no antibodies)
As the majority of death from chickenpox is caused by secondary bacterial infection specifically Group A Streptococcus or Staphlococcus Aureas infections, blood cultures and skin swabs are essential. Intravenous antibiotics should be commenced especially if pyrexia does not settle, or infection is suspected.
We generally say that if a fever in a child with chicken pox goes beyond the fourth day of illness, then you need to look for another cause. In many cases, the threshold for IV antibiotics is very low.
[Editor’s note: In the current climate of higher Group A Strep levels in the community, a child with chicken pox who is unusually unwell, has a prolonged fever or any signs and symptoms which can not be attributed to chicken pox- like respiratory symptoms, joint pains or skin problems (cellulitis/necrotising fasciitis) – should set off red flags for secondary bacterial infection.]
Given the extremely infectious nature of chickenpox, hospitalised children should be isolated, and barrier nursed whilst they are infectious
Conclusion: Despite being rare, severe complications of chickenpox are deadly and management in the youngest remains a clinical challenge. Whilst randomised controlled trials in this area are limited, experts agree that aggressive preventative therapies particularly around delivery is essential. To avoid unnecessary hospitalisation, the clinical status of individual patients should be carefully considered including age/time of exposure and risk factors for serious disease.
In the current climate of high circulating levels of group A strep, be mindful of opportunistic infection in a child with chicken pox with signs and symptoms which can not be attributed to the disease.
References
[1] National Institute for Health and Care Excellence. Chickenpox. June 2022.
[2] Cameron JC, Allan G, Johnson F, Finn A, Heath PT, Booy R. Severe complications of chickenpox in hospitalisaed children in the UK and Ireland. Arch Dis Child 2007;92:1062-1066.
[3] Blumental S, Lepage P. Management of varicella in neonates and infants. BMJ Paediatrics Open2019;3;e000433.
Landing page image: Chickenpox via DermNet.