Dermatology
Question 145 of 180
A 6 year old girl is brought to the Emergency Department with a 2 day history of a widespread, itchy red rash. You are able to diagnose chickenpox. The child's mother asks about exclusion from school. What is the advice regarding the school exclusion period for chickenpox?
Answer:
- Patient advice:
- Advise that the most infectious period is 1–2 days before the rash appears, but infectivity continues until all the lesions are dry and have crusted over (usually about 5 days after the onset of the rash).
- During this time, advise a person with chickenpox to avoid contact with:
- People who are immunocompromised
- Pregnant women
- Infants aged 4 weeks or less
- Advise that children with chickenpox should be kept away from school or nursery until all the vesicles have crusted over.
Chickenpox
Dermatology
Last Updated: 1st June 2023
Chickenpox is an acute disease caused by varicella-zoster virus. It is characterised by a vesicular rash, often preceded by fever and malaise. Chickenpox is predominantly a childhood illness; its incidence is highest before 10 years of age. As chickenpox is a common childhood disease, more than 90% of people older than 15 years of age in England and Wales are immune (seropositive for varicella-zoster immunoglobulin G).
Transmission
- Varicella is very infectious; up to 90% of susceptible contacts develop the disease.
- Transmission is by personal contact or droplet spread, with an incubation period of 1–3 weeks.
- Chickenpox is infectious from 1–2 days before the rash appears until the vesicles are dry or have crusted over, usually 5 days after the onset of the rash (this period may be longer in people who are immunocompromised).
- Once the infection has subsided, the virus persists in sensory nerve root ganglia. Years or decades later, it can reactivate and cause herpes zoster (shingles)
- It is possible to develop chickenpox after exposure to a person with shingles, but it is not possible to develop shingles from exposure to a person with chickenpox.
Clinical features
In most cases, the diagnosis can be made clinically from the characteristic chickenpox rash. If there is doubt, a history of recent exposure to chickenpox (or shingles), or cases occurring in close contacts, may help confirm the diagnosis.
Clinical features include:
- A prodrome that includes nausea, myalgia, anorexia, and headache (particularly adolescents and adults)
- General malaise, loss of appetite, and feeding problems
- Fever
- Characteristic rash
- Small, erythematous macules appear on the scalp, face, trunk, and proximal limbs, which progress over 12–14 hours to papules, clear vesicles (which are intensely itchy), and pustules.
- Vesicles can also occur on the palms and soles, and mucous membranes can also be affected, with painful and shallow oral or genital ulcers.
- Vesicles appear in crops; stages of development of the rash can therefore differ on different areas of the body.
- Crusting occurs usually within 5 days of the onset of the rash, and crusts fall off after 1–2 weeks.
Differential diagnosis
- Other vesicular viral rashes, such as:
- Herpes simplex (not usually disseminated)
- Herpes zoster (usually unilateral and localised to dermatomes)
- Hand, foot, and mouth disease (caused by Coxsackie virus)
- Other infections, such as:
- Impetigo
- Scabies
- Syphilis
- Meningococcaemia (can be confused with haemorrhagic varicella)
- Toxic shock syndrome
- Skin disorders, such as:
- Guttate psoriasis
- Drug eruption
- Insect bites
- Papular urticaria
- Erythema multiforme
- Stevens–Johnson syndrome
- Henoch–Schönlein purpura
- Dermatitis herpetiformis
Management
For otherwise healthy children and adults:
- If serious complications (such as pneumonia, encephalitis, or dehydration, or severe secondary bacterial infection of the skin) are suspected, admit to hospital.
- Antiviral treatment:
- Consider prescribing oral aciclovir 800 mg 5 times a day for 7 days for an immunocompetent non-pregnant adult or adolescent (aged 14 years or older) with chickenpox who presents within 24 hours of rash onset, particularly for people with severe chickenpox or those at increased risk of complications, such as smokers.
- Aciclovir is not recommended for otherwise healthy children with chickenpox.
- Symptomatic treatment:
- Paracetamol if pain or fever are causing distress (avoid nonsteroidal anti-inflammatory drugs)
- Topical calamine lotion to alleviate itch
- Chlorphenamine for treating itch associated with chickenpox for people 1 year of age or older
- Patient advice:
- Advise that the most infectious period is 1–2 days before the rash appears, but infectivity continues until all the lesions are dry and have crusted over (usually about 5 days after the onset of the rash).
- During this time, advise a person with chickenpox to avoid contact with:
- People who are immunocompromised
- Pregnant women
- Infants aged 4 weeks or less
- Advise that children with chickenpox should be kept away from school or nursery until all the vesicles have crusted over.
Complications
- Complications in children
- Chickenpox is usually a self-limiting disease in healthy children, and complications are rare. However, complications may occur, including:
- Skin bacterial superinfection (for example impetigo, furuncles, cellulitis, erysipelas, necrotising fasciitis) and scarring
- Neurological complications (for example Reye's syndrome, acute cerebellar ataxia, encephalitis, meningoencephalitis, polyradiculitis, myelitis)
- In rare cases, myocarditis, glomerulonephritis, appendicitis, pancreatitis, Henoch–Schönlein purpura, orchitis, arthritis, optic neuritis, iritis, and keratitis
- Chickenpox is usually a self-limiting disease in healthy children, and complications are rare. However, complications may occur, including:
- Complications in adults
- Chickenpox can be more serious in adults than in children, and adults with varicella are more likely to be admitted to hospital. Complications include pneumonia, hepatitis, and encephalitis. Shingles can occur from reactivation of latent varicella-zoster infection.
- Complications in pregnancy
- Varicella in pregnancy can result in severe chickenpox. The mother is at increased risk of varicella pneumonia and other complications, compared with the general adult population.
- Infection with varicella-zoster during the first 28 weeks of pregnancy can lead to intrauterine infection and fetal varicella syndrome, which is characterised by one or more of:
- Skin scarring in a dermatomal distribution
- Eye defects (for example microphthalmia, chorioretinitis, and cataracts)
- Hypoplasia of the limbs
- Neurological abnormalities (microcephaly, cortical atrophy, learning difficulties, dysfunction of bowel and bladder sphincters)
- Complications in neonates
- Neonates are at increased risk of disseminated or haemorrhagic varicella. If the mother becomes infected 1–4 weeks before delivery, up to half of babies will be infected; and around a quarter will develop clinical varicella of the newborn, even though they have passively acquired maternal antibody.
Post-exposure prophylaxis
For all people with a history of exposure to chickenpox, establish whether:
- The diagnosis of chickenpox in the contact is certain.
- The exposure was significant enough to put the person at risk of infection (see below).
- The person has had chickenpox in the past.
- The person is at increased risk of complications of chickenpox (for example pregnant women, immunocompromised people, and neonates).
- The person is in contact with others at high risk of complications (for example healthcare workers).
Defining a significant exposure:
Three aspects of exposure to VZV during the infectious period are relevant when considering the need for post-exposure prophylaxis (PEP) for a susceptible high risk individual.
- The type of varicella-zoster infection in the index case. Exposure is significant if the person has had contact with:
- Chickenpox.
- Disseminated shingles.
- Immunocompetent people with exposed shingles lesions (for example ophthalmic zoster).
- Immunocompromised people with localized shingles on any part of the body (because this group may have increased viral shedding).
- The timing of exposure in relation to the rash onset in the index case. Exposure is significant if the person was in contact with:
- Chickenpox — from 48 hours before onset of rash to crusting of lesions.
- Disseminated shingles — from 48 hours before onset of rash to crusting of lesions.
- Localized shingles — day of onset of rash until crusting of lesions.
- Closeness and duration of contact. Exposure is significant if it is through:
- Maternal/neonatal contact.
- Continuous home contact.
- Contact in the same room (for example house or classroom) for 15 minutes or more, or contact on large open wards (particularly paediatric wards).
- Face-to-face contact (for example having a conversation).
Assessing susceptibility:
The administration of varicella zoster immunoglobulin (VZIG) is unlikely to confer any additional benefit for patients who already have varicella antibody (VZV IgG) and therefore VZIG is not recommended for individuals with adequate levels of VZV IgG. Assessment of susceptibility will depend on the history of previous infection or vaccination, and the underlying clinical condition.
- For immunocompetent individuals including pregnant women, a history of previous chickenpox, shingles or 2 doses of varicella vaccine is sufficient evidence of immunity. In those without such a history, urgent antibody testing should be undertaken on a recent blood sample (booking blood samples are acceptable for pregnant women if available). PEP (antivirals or VZIG, if antivirals contraindicated) should be offered if VZV IgG is <100 mIU/ml.
- For immunosuppressed patients, a history of previous infection or vaccination is not a reliable history of immunity and VZV antibody levels should be checked urgently. Individuals with VZV antibody levels of 150 mIU/ml or greater are unlikely to benefit from VZIG, and therefore individuals with VZV IgG <150 mIU/ml in a quantitative assay, or negative or equivocal in a qualitative assay should be offered PEP. Qualitative or quantitative antibody testing is required for all immunosuppressed patients where VZIG is being considered (such as individuals in whom antivirals are contraindicated).
Management:
Perform a general assessment to establish the person's risk of chickenpox on the basis of their history of chickenpox, the certainty of chickenpox in the contact, and the level of exposure.
- For otherwise healthy immunocompetent adults and children:
- If the person's exposure to chickenpox is not significant, or if they have a history of chickenpox, or if they are known to be immune to chickenpox, reassure.
- If the person is not immune, advise them that they may develop chickenpox.
- For healthcare workers:
- If they have a definite history of chickenpox or shingles and have had a significant exposure to the varicella-zoster virus, they can continue working as they are considered to be protected, however, if they develop a rash or fever, or feel unwell they should seek advice from occupational health before patient contact.
- If they are not vaccinated and do not have a definite history of chickenpox or shingles, they should avoid contact with high-risk patients for 8–21 days from exposure and contact their occupational health department.
- For pregnant women:
- If the woman has a definite history of chickenpox or shingles or two doses of a varicella containing vaccine, and is not immunocompromised, reassure her that she is not at risk of chickenpox because immunity can be assumed.
- If the woman has no history of chickenpox or shingles (or is uncertain) and has a history of significant contact, establish the stage of gestation and seek urgent specialist advice. Testing for varicella-zoster immunoglobulin G (IgG) antibodies is indicated.
- If the test shows varicella-zoster immunoglobulin G antibodies (evidence of immunity from past infection or immunization), the woman can be reassured that she is immune.
- If the woman's antibody status is negative, urgently discuss with a specialist the need for prophylaxis.
- For neonates:
- If the neonate's mother is the contact, determine when, in relation to delivery, she developed chickenpox. If someone else is the contact, determine the age of the neonate at the time of contact.
- Seek urgent specialist advice regarding the need for testing and further management, and whether the mother should continue to breastfeed if she has chickenpox.
- For immunocompromised people:
- Seek same-day specialist advice regarding testing and management.
Post-exposure prophylaxis with aciclovir [unlicensed use] is recommended first line for at risk individuals, except for certain susceptible neonates and for individuals for whom antivirals are contraindicated or otherwise unsuitable (e.g. if there are significant concerns about renal impairment or intestinal malabsorption), where varicella-zoster immunoglobulin (VZIG) is recommended instead.
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
