Disease overview

Viral

Varicella

水痘

Evidence-backed informationEN 6/7 applicable sections · ZH 6/7 applicable sectionsUpdated Sep 3, 2026

Varicella (chickenpox) is a highly contagious disease caused by the varicella-zoster virus (VZV), a member of the herpesvirus family for which humans are the only known natural hosts ^[1]. The virus is found worldwide, and primary infection results in chickenpox; after recovery, the virus becomes inactive in nerve cells and can reactivate later as shingles (herpes zoster) ^[1]^[2]. The disease tends to occur more often during winter and spring or cool and dry months, with outbreaks occurring every 2–5 years ^[1]. While typically mild in children, varicella can be more severe in adolescents and adults ^[1]^[2].

Read the full clinical and epidemiological profile7

Definition

Varicella, commonly known as chickenpox, is a febrile vesicular rash disease caused by primary infection with the varicella-zoster virus (VZV), also called human herpesvirus 3 ^[1]^[2]. After primary infection, VZV establishes latency in peripheral ganglia, and reactivation decades later causes herpes zoster (shingles) ^[3]. VZV is the only human herpesvirus for which highly effective vaccines are available ^[2].

Clinical features

Primary varicella presents as a febrile illness with a characteristic vesicular rash that progresses from macules to papules, vesicles, pustules, and crusts ^[2]. The disease can be more severe in immunocompromised individuals, infants, and adults ^[2]^[3]. Complications may include secondary bacterial infection of skin lesions, pneumonia, and encephalitis ^[2]. Following primary infection, VZV establishes latency in ganglionic neurons; reactivation can lead to postherpetic neuralgia and other neurological syndromes ^[2]^[3].

Epidemiology

VZV is found worldwide, with chickenpox occurring more frequently during winter and spring or cool and dry months ^[1]. Epidemics typically occur every 2–5 years ^[1]. The disease is generally mild in children but tends to be more severe in adolescents and adults ^[1].

Transmission

The virus spreads through respiratory droplets when someone with chickenpox coughs or sneezes, releasing infected droplets into the air, and through direct contact with fluid from the chickenpox blisters ^[1]. Susceptible individuals—those who have not had chickenpox or been vaccinated—are highly likely to contract the virus upon exposure ^[1].

Prevention

VZV is the only human herpesvirus for which highly effective vaccines are available ^[2]. A live attenuated varicella vaccine is used to prevent chickenpox, primarily in children ^[2]^[3]. Vaccination establishes latency similar to wild-type infection, and long-term immunity to varicella develops after either natural infection or vaccination ^[2]. However, immunity from vaccination or prior infection does not protect against reactivation leading to shingles ^[2].

Surveillance note

GlobalID source-data note: Ireland and Japan publish varicella series restricted to hospitalised cases, while other countries report broader notification or sentinel series. Hospitalised-case counts measure a severe subset and should not be interpreted as all community varicella or compared directly with unrestricted series.

References

1World Health Organization. Chickenpox [Internet]. cited 2 Sept 2026.Available from: https://www.who.int/news-room/questions-and-answers/item/chickenpox
2Gershon AA et al. Varicella zoster virus infection. Nat Rev Dis Primers. 2015 Jul 2. PMID: 27188665. doi: 10.1038/nrdp.2015.16.PubMed: https://pubmed.ncbi.nlm.nih.gov/27188665/
3Kennedy PGE et al. Clinical Features of Varicella-Zoster Virus Infection. Viruses. 2018 Nov 2. PMID: 30400213. doi: 10.3390/v10110609.PubMed: https://pubmed.ncbi.nlm.nih.gov/30400213/
4Patil A et al. Herpes zoster: A Review of Clinical Manifestations and Management. Viruses. 2022 Jan 19. PMID: 35215786. doi: 10.3390/v14020192.PubMed: https://pubmed.ncbi.nlm.nih.gov/35215786/

Coding Register

ICD-10: B01
ICD-11: KA62.0

Key Statistics

Total cases: 5.3M
Total deaths: 1
Peak month: 2026-06
Coverage: 9 reporting countries · 1924-01-01 → 2026-09-01

Coverage

Reporting countries and regions

9 locations

Trends by reporting country

Monthly patterns over time

Research Radar

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Showing 5 of 11 related publications.

Literature links are provided for discovery and do not alter or validate the surveillance series above.

Rows5,545

Updated2026-09-01

Coverage—

Partitions17

Source9 series · 2,431 observations

Official sourcesAuthority, cadence, notes87

monthlymicrosoft_bi

Australian national notifiable diseases surveillance dashboard.

monthlymicrosoft_bi

Australian NINDSS monthly state/territory notifications for Australian Capital Territory, kept separate from the Australia national aggregate.

monthlymicrosoft_bi

Australian NINDSS monthly state/territory notifications for New South Wales, kept separate from the Australia national aggregate.

monthlymicrosoft_bi

Australian NINDSS monthly state/territory notifications for Northern Territory, kept separate from the Australia national aggregate.

monthlymicrosoft_bi

Australian NINDSS monthly state/territory notifications for Queensland, kept separate from the Australia national aggregate.

monthlymicrosoft_bi

Australian NINDSS monthly state/territory notifications for South Australia, kept separate from the Australia national aggregate.

monthlymicrosoft_bi

Australian NINDSS monthly state/territory notifications for Tasmania, kept separate from the Australia national aggregate.

monthlymicrosoft_bi

Australian NINDSS monthly state/territory notifications for Victoria, kept separate from the Australia national aggregate.

monthlymicrosoft_bi

Australian NINDSS monthly state/territory notifications for Western Australia, kept separate from the Australia national aggregate.

monthlyftp_dbc

Brazil Ministry of Health DATASUS/SINAN public DBC microdata aggregated to national monthly notification counts.

ANNUALweb

Canada is the national jurisdiction; subdivision feeds are registered separately.

monthlymicrosoft_bi

Ontario-level current-year preliminary monthly case counts from Public Health Ontario's IDTO report.

MONTHLYweb

Monthly notifiable infectious disease reports published by China CDC.

MONTHLYweb

Official China public health bulletin and query portal.

MONTHLYweb

Biomedical literature discovery feed used as supplementary context.

annualofficial_datacenter_spreadsheet

Chinese province-level historical monthly observations; this higher-priority source overlays overlapping official monthly reports.

monthlyofficial_provincial_report