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Chickenpox - Background information
What is it?
- Chickenpox is an acute disease caused by varicella-zoster virus. It is characterized by a vesicular rash, and often fever and malaise [Heininger and Seward, 2006].
- Varicella is very infectious; up to 90% of susceptible contacts develop the disease [HPA, 2006].
- Transmission is by personal contact or droplet spread, with an incubation period (the time from becoming infected until symptoms appear) of 1–3 weeks [DH, 2006; HPA, 2006].
- Chickenpox is infectious from 1–2 days before the rash appears until the vesicles are dry or have crusted over, usually 5–6 days after the onset of the illness (this period may be longer in people who are immunosuppressed) [DH, 2006; HPA, 2006].
- Once the infection has subsided, the virus persists in sensory nerve ganglia of the dorsal root. Years or decades later, it can reactivate and cause herpes zoster (shingles). See the CKS topics on Post-herpetic neuralgia and 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 [HPA, 2006].
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