Varicella and herpes zoster (Human)

Primary reference(s)

WHO, 2014. Biologicals: Varicella. World Health Organization (WHO). Accessed 13 December 2019.

Additional scientific description

Varicella zoster virus (VZV) is a member of the herpesvirus family. Only one serotype of VZV is known, and humans are the only reservoir (WHO, 2014).

Following infection, the virus remains latent in neural ganglia and in some cases, it is reactivated to cause herpes zoster, or shingles, generally in elderly or immunocompromised individuals (WHO, 2014).

Initial infection with VZV causes varicella (or chickenpox). While mostly a mild disorder in childhood, varicella tends to be more severe in adults. It may be fatal, especially in neonates and in immunocompromised persons. Infection during early pregnancy can rarely lead to destructive lesions in the foetus with shingles-like scarring of tissues (Lamont et al., 2011).

Varicella is characterised by an itchy rash of small blisters, usually starting on the scalp and face and initially accompanied by fever and malaise. The rash gradually spreads to the trunk and limbs but tends to spare the hands and feet. The blisters gradually dry out and crusts appear which then disappear over a period of one to two weeks (WHO, 2014).

The infection may occasionally be complicated by pneumonia or encephalitis (inflammation of the brain), at times with serious or fatal consequences (WHO, 2014).

Shingles is a painful rash, usually affecting a zone on one side of the face or body, that may occasionally result in permanent damage to the nerves or cause visual impairment. In immunosuppressed individuals it is severe and often dangerous but can be treated with antiviral medicines (WHO, 2014).

VZV transmission occurs via droplets, aerosols, or direct contact with respiratory secretions, and almost always produces clinical disease in susceptible individuals. Shingles is less infectious than chickenpox as the rash is limited and respiratory involvement is much less common (WHO, 2014).

The World Health Organization (WHO) has published guidance on case classification and surveillance standards (WHO, 2018).

Metrics and numeric limits

Not applicable.

Examples of drivers, outcomes and risk management

Although varicella is usually self-limiting it may be associated with severe complications, mediated either by VZV or secondary bacterial infection. Extra-cutaneous complications affecting the central nervous system range from cerebellar ataxia to encephalitis (WHO, 2014).

The most common complications in children are secondary bacterial infections. VZV pneumonia frequently with secondary bacterial infection is the most common complication in adults. Groups at higher risk for severe complications are neonates, infants, pregnant women, older adults, and immunocompromised persons – including those who are taking oral corticosteroids (WHO, 2014).

Supportive measures include relief of chickenpox symptoms, prevention of skin infections and prompt treatment for pneumonia which often needs both antivirals and antibiotics as staphylococcal superinfection is very common. Intake of fever medications may help symptoms, but caution must be observed in children (WHO, 2014).

The best way to prevent chickenpox is to get the chickenpox vaccine (WHO, 2014).

Severe or complicated cases including susceptible pregnant women can be treated with appropriate antiviral medicines (WHO, 2014).