Chickenpox is caused by the varicella-zoster virus (VZV), also known as human herpes virus 3 (HHV-3), one of the eight herpes viruses known to affect humans. It starts with conjunctival and catarrhal symptoms, moderate fever and then characteristic spots appearing in two or three waves, mainly on the body and head rather than the hands and becoming itchy raw pox (pocks), small open sores which heal mostly without scarring.
Chickenpox has a 10-14 day incubation period and is highly contagious by air transmission two days before symptoms appear. Following primary infection there is usually lifelong protective immunity from further episodes of chickenpox. Recurrent chickenpox is fairly rare but more likely in people with compromised immune systems.
Symptomatic treatment, with calamine lotion to ease itching and paracetamol (American English: acetaminophen) to reduce fever, is widely used.
Chickenpox is rarely fatal (usually from varicella pneumonia), with pregnant women and those with depressed immune systems being more at risk. Pregnant women not known to be immune and who come into contact with chickenpox may need urgent treatment as the virus can cause serious problems for the fetus.
Later in life, viruses remaining dormant in the nerves can reactivate causing localised eruptions of shingles. This occurs particularly in people with compromised immune systems, such as the elderly, and perhaps even those suffering sunburn. Unlike chickenpox which normally fully settles, shingles may result in persisting post-herpetic neuralgia pain.
A chickenpox vaccine has been available since 1995, and is now required in some countries for children to be admitted into elementary school unless the parent/guardian submits an exemption. In addition, effective medications (e.g. aciclovir) are available to treat chickenpox in healthy adults and immunocompromised persons.
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