Causative Agent
Varicella-zoster virus.
Clinical Description
Chickenpox (varicella) is an acute, generalised viral disease resulting
from primary infection with varicella-zoster virus. Onset is sudden
with mild fever, malaise and a characteristic itchy vesicular rash.
Successive crops of lesions can appear, drying to a granular scab after
three to four days. The highest rate of infection occurs in pre-school
children and almost everyone is infected by adulthood. Varicella-zoster
virus establishes latency after infection and may be re-activated, usually
in later life, as herpes zoster (shingles).
Chickenpox is generally not a serious infection, but complications,
including encephalitis, pneumonia and secondary bacterial infection,
can occur in previously healthy individuals.
Chickenpox is most serious for pregnant women, and immunocompromised
individuals and exposed neonates, who are at risk of severe, disseminated
disease.
Transmission
Respiratory transmission from infected individuals, by direct contact
with vesicles, or indirectly via fomites. The incubation period is two
to three weeks. An individual may be considered infectious from two
days prior to vesicle formation until the last vesicles are crusted.
Surveillance in Scotland
- Laboratory reports for varicella zoster virus.
- Until 31 December 2009 there was statutory notification of chickenpox by clinical diagnoses. The Public Health etc (Scotland) Act Part 2 (Notifiable Diseases, Notifiable Organisms and Health Risk Status) came into effect on 1 January 2010. Under this Act, chickenpox is no longer a notifiable disease in Scotland.
Laboratory Report
Varicella zoster virus reports with mention of chickenpox, or varicella
in the clinical field.
Incidence
Notifications for chickenpox peak annually between February and August,
but there is no apparent epidemic cycle.
Chickenpox Notifications
Scotland 2000-2009
Year |
Notifications (all ages) |
2000 |
24787 |
2001 |
21894 |
2002 |
28407 |
2003 |
19875 |
2004 |
21333 |
2005 |
15896 |
2006 |
16877 |
2007 |
19898 |
2008 |
12181 |
2009 |
16569 |
Prevention
Chickenpox is now a vaccine preventable disease with the advent of
a live attenuated varicella zoster virus vaccine. Two live varicella
vaccines are licensed in the UK and recommended for susceptible healthcare
workers and other contacts of immunocompromised patients in certain
circumstances. Varicella zoster vaccine has been used in Japan for many
years, and is now part of the routine childhood immunisation schedule
in some countries, including Canada and the United States. Passive protection
against primary varicella zoster infection may be attained via administration
of human varicella-zoster immunoglobulin. Prophylaxis is recommended
for susceptible individuals at high risk of severe varicella with significant
exposure to chickenpox.
Herpes Zoster
After initial infection with varicella-zoster virus (chickenpox), the virus becomes latent within the dorsal root ganglia, and can re-activate later, resulting in herpes zoster (shingles). Whilst reactivation can occur at any age, the age specific incidence increases with age.
The JCVI (Joint Committee on Vaccination and Immunisation) reviewed the available evidence for herpes zoster vaccination and made the following recommendation:
'JCVI reviewed medical, epidemiological, and economic evidence as well as vaccine safety and efficacy data relevant to a herpes zoster (shingles) vaccination programme. Based on the evidence, a universal herpes zoster vaccination programme for adults aged 70 years up to and including 79 years is recommended provided that a licensed vaccine is available at a cost effective price. A universal varicella vaccination for children is not recommended. These recommendations will be kept under review in light of emerging data on the epidemiology of varicella and herpes zoster infections and the cost-effectiveness of vaccines against these infections.'
Further Information
Notifications of infectious diseases
Last reviewed: 14 December 2010
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