Chickenpox (VZV)

Chickenpox (VZV)

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Chickenpox is a common viral infection caused by the varicella-zoster virus (VZV). Over 75% of children are infected with VZV before age five.


VZV is a DNA virus of the herpesviridae family. Transmission is via droplet spread or direct skin contact with vesicle fluid, with the virus entering the body through the upper respiratory tract.

Clinical features

Chickenpox is an acute disease, characterised by a vesicular rash associated with fever and malaise. The incubation period is typically 10-14 days but can be up to 21 days.

Symptoms are milder in younger children (once past the neonatal stage) and more severe in adults.


Prodromal symptoms can last up to four days and include the following:

  • High fever (38-39°C)
  • General malaise
  • Myalgia
  • Anorexia
  • Headache
  • Nausea


As the prodromal period ends, the characteristic rash develops:

  • It begins as small erythematous macules on the scalp, face, trunk and proximal limbs
  • These macules develop into papules, vesicles and pustules which appear in crops
  • Vesicles may be found on the palms, soles and mucous membranes, and are especially itchy
  • Shallow oral and genital ulcers can also occur, which are painful
  • Crusting of the vesicles and pustules usually occurs in five days, at which point new vesicle formation has ceased

Differential diagnoses

There are several differential diagnoses for chickenpox (Table 1).3

Table 1.Differential diagnoses of chickenpox (VZV)

DifferentialNotesVesicular viral rashes Herpes simplex (HSV) Vesicles are usually more localised i.e. cold sores (except in eczema herpeticum- disseminated HSV) Herpes zoster (VZV) Also known as shingles -a reactivation of VZV usually localised to a unilateral dermatome Hand, foot and mouth disease (Coxsackie A virus) This rash presents as vesicles localised to the hands and feet, with ulcers in the mouth Other infections Impetigo (usually strep or staph) Pustules which develop into golden crusted lesions, usually on the face Scabies (mites) Erythematous papular rash usually starting between the fingers Skin disorders Guttate psoriasis, drug eruptions, dermatitis herpetiform, insect bites


Chickenpox is a clinical diagnosis, and investigations are not generally required unless there are concerns about complications. If diagnostic confirmation is needed, lesion scrapings can be tested.


General advice

To prevent complications and the spread of the virus, good hydration and avoiding scratching, pregnant women, neonates and immunocompromised individuals is recommended.

Symptomatic management

Symptomatic management includes taking paracetamol for fever and discomfort, avoiding NSAIDs as they increase the risk of necrotising soft tissue infections, taking sedating antihistamines (chlorphenamine), emollients and calamine lotion for itch, and considering oral aciclovir within 24 hours of rash onset for adolescents and adults.

Treatment in high-risk groups

Management may differ for immunocompromised patients (e.g. neonates, pregnant women, breastfeeding women) due to the increased risk of severe disease. Specialist advice should be sought and further management options may include antiviral medication such as aciclovir and intravenous immunoglobulin.

Treatment of complications

Secondary bacterial skin infection and pneumonia require antibiotics and hospital admission is likely to be necessary for those with severe disease or complications.

Public health requirements

Chickenpox is a notifiable disease in Scotland and Northern Ireland, but not in England or Wales. Children should not return to school until all lesions are crusted over due to the highly infectious nature of the virus. No mass vaccination programme is available in the UK.


In healthy children, chickenpox is usually self-limiting. However, complications occur more frequently in neonates, pregnant women, immunocompromised patients, very young or older patients. Complications may include dehydration, secondary bacterial infection of lesions, scarring, viral pneumonia, encephalitis and Reye's Syndrome, which is a rare condition seen in children and young adults. This may be related to the use of aspirin, which should be avoided in children.


The VZV virus stays dormant in the sensory nerve ganglia of the dorsal root and can reactivate as herpes zoster (shingles) many years later.

High-risk populations

Chickenpox in pregnancy

If chickenpox is contracted before 20 weeks gestation there is a risk of congenital varicella syndrome, which is characterised by intrauterine growth restriction, microcephaly, limb hypoplasia, ophthalmological defects and cutaneous scarring. After 20 weeks gestation, maternal chickenpox infection can cause neonatal herpes zoster (shingles) or preterm labour. Once a person has had chickenpox they are usually immune if immunocompetent, with second episodes thought to be rare.

Maternal Chickenpox

Maternal chickenpox can be severe, with a high risk of pneumonia for the mother.

Chickenpox in Neonates

There is a risk of neonatal chickenpox if the maternal rash appears during a seven day period before, to two days after delivery. This is due to the transplacental transmission of the virus, but not the initial IgM antibodies. Neonatal chickenpox has a 30% mortality rate, which is usually caused by severe pneumonia or fulminant hepatiits. Treatment includes aciclovir and immunoglobulin.

Chickenpox in Immunocompromised Individuals

Immunocompromised individuals are at greater risk of developing severe disseminated chickenpox, varicella pneumonia, encephalitis, hepatitis, and haemorrhagic complications.

Key Points

  • Chickenpox is a very common and highly infectious viral infection.
  • The characteristic rash begins as macules, progressing to papules, vesicles, pustules and eventually crusting over. Crops of different stages are found at different sites.
  • Chickenpox is generally self-limiting in the immunocompetent and only symptomatic treatment is required.
  • Aciclovir can be used in high risk or severe cases.
  • Complications include pneumonia, encephalitis and secondary bacterial infection.
  • Pregnant women are at risk of congenital varicella syndrome, preterm labour or neonatal chickenpox.
  • VZV can re-emerge as shingles later in life.


Chickenpox is an infection caused by the varicella-zoster virus. It is also known as varicella and is a highly contagious disease. It is mostly found in children but can also affect adults. It is characterized by an itchy, spotty rash on the skin and can be very uncomfortable. The rash usually appears on the face, chest, and back and can be accompanied by fever, headaches, and fatigue. The rash tends to form blisters that eventually crust over. The chickenpox rash usually lasts for 5 to 10 days.

Complications of chickenpox may include pneumonia, inflammation of the brain, bleeding problems, and skin infections. In rare cases, chickenpox can be serious and even fatal. Children and adults with weakened immune systems are at a higher risk of developing serious complications.

Chickenpox is spread through the air by coughing and sneezing and by direct contact with fluid from the blisters. The disease can also be spread through contact with items that have been contaminated with the virus. An infected person is contagious 1 to 2 days before the rash appears and for the 5 to 7 days that the rash is present. After the rash disappears, the person is no longer contagious.

Treatment for chickenpox focuses on relieving symptoms and preventing complications. This includes getting plenty of rest, taking lukewarm baths, and applying calamine lotion to soothe the itching. Pain relievers such as acetaminophen and ibuprofen can also be used to reduce fever. Anti-itch medicines such as diphenhydramine and hydrocortisone can be used for more severe itching. A doctor may also prescribe antiviral medications to reduce the severity and duration of the infection.

Chickenpox can be prevented with the varicella vaccine. It is recommended for all children over the age of 12 months and for adults who have never had chickenpox and are not vaccinated. The vaccine is more than 90% effective in preventing the disease.

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