Chicken pox Flashcards
Define
Varicella zoster virus (HHv-3) – reactivation of dormant virus after chickenpox leads to herpes zoster (shingles)
o Incubation period = 10-21 days
o Infectious period = 48 hours before rash to last crusted over lesion / 5-7 days after rash appears
Signs and symptoms
Pyrexia, headache, abdominal pain, malaise
Crops of vesicles appear over 3-5 days:
- Head, neck, trunk (less on limbs) – itchy
- Papule → vesicle → crust – several stages at once
Investigations: clinical diagnosis
Management
Supportive (virus; fluids, analgesia, rest)
NO IBUPROFEN: it increases the risk for seconday skin bacterial infection (necrotising fasciitis)
o Advice – nails short, loose clothing, infectious period = 1-2 days before rash to last crusted over lesion
o Isolate from:
1. Immunocompromised Neonates (<28d old)
2. Pregnant women
3. Keep home from school
o Special cases:
- Admit if serious complications (e.g. pneumonia, encephalitis, dehydration)
- Secondary bacterial superinfection -> sudden high fever: toxic shock, necrotising fasciitis
- Encephalitis (ataxic with cerebellar signs; better prognosis than HSV-encephalitis)
- Purpura fulminans -> large necrotic loss of skin from cross-activation of antiviral ABs -> inhibit the inhibitory coagulation proteins factors C and S -> increased clotting and purpuric skin rash
- Dehydration (severe)
Immunocompetent adolescents/adults -> oral aciclovir 800 mg 5/day for 7 days (if <24hrs of rash)
Immunocompromised children -> IV aciclovir -> oral aciclovir
· Prophylactic prevention = human VZV IVIG if born +- 7 days from when mom developped rash
Complications
Secondary Bacterial Infection
- Mainly with staphylococci and group A streptococci
- May lead to further complications e.g. toxic shock syndrome or necrotising fasciitis
- Strep pyogenes is the most common cause of invasive skin infection (followed by staph a)
- This should be considered where there is onset of a new fever or persistent high fever after the first few days
GIVE IV FLUCOXACILLIN AND ACICLOVIR
Encephalitis
- This may be generalised, usually occurring EARLY during the illness
- The prognosis is GOOD (in contrast to the encephalitis caused by HSV)
- Most characteristic is a VZV-associated cerebellitis
- This usually occurs about 1 week after the onset of rash
- The child is ataxic with cerebellar signs
- It usually resolves within a month
Purpura Fulminans
- This is the consequence of vasculitis in the skin and subcutaneous tissues
- Often related to meningococcal disease
- Can lead loss of large areas of skin due to necrosis
- Rarely, it can occur after VZV infection due to production of antiviral antibodies which cross-react and inactivate the inhibitory coagulation factors Protein C or Protein S, resulting in increased risk of clotting- this often manifests as a purpuric rash
If the patient is immunocompromised, primary varicella infection may result in progressive disseminated disease which has a mortality of up to 20%.
The vesicular eruptions persist and may become haemorrhagic.
