Resource Packages: Chicken Pox (Varicella)

Historical Overview

Until the middle of the 18th century, chickenpox was regarded as a mild form of smallpox and, indeed, clinically the two diseases may occasionally be difficult to differentiate.  However, in view of the fact that smallpox has been virtually eradicated worldwide, the difficulty of separating the two conditions has almost become academic.  

Varicella (chickenpox) is a highly contagious disease that is caused by Herpesvirus varicellae. Chickenpox is also known as Herpes Zoster, Varicella-Zoster and Varicella-Zoster Virus. 

Chickenpox occurs when a person is infected with the virus for the first time. Shingles, which occurs mainly in older adults and immunosuppressed individuals, represents recurrence of latent infection. 

Recent Developments

Chickenpox is an acute, generalised viral disease with sudden onset of slight fever, a mild disease of short duration in healthy children, but can cause severe and even fatal illness in immunosuppressed patients. 

Neonates developing varicella between ages 5 and 10 days, and those whose mothers develop the disease 5 days prior to or within 2 days after delivery, are at an increased risk of developing severe generalised chickenpox, with a case fatality of up to 30%.   

In children, the development of a vesicular rash is generally the first indication of disease.  Spots appear first on the trunk followed by the face and scalp, and spread to the limbs tends to be comparatively slight.  Lesions may be so few as to escape observation.  

An individual lesion is usually superficial and rapidly progresses through the stages of papule, vesicle and pustule, which ultimately dries and forms a scab.  This process takes about 48 hours.  The rash, however, develops in successive crops during the first few days of the illness and results in lesions being present at all stages of development after the first 24 hours.  All lesions are dry and crusts begin to separate by the end of the week. 

Adult cases are usually more severe with a short febrile illness followed by a profuse rash which may involve the mouth, throat and conjunctiva.  Skin irritation, which is usually mild in children, may be severe in adults.  

Chickenpox is one of the most easily transmitted communicable diseases and spreads from person to person by direct contact, droplet, or airborne spread of secretions of the respiratory tract of chickenpox cases or from a secondary spread from the discharging vesicles and mucous membranes of infected patients. 

INCUBATION PERIOD is 11 to 21 days, usually 14-16 days post exposure.

 

Communicability   

Health care workers (HCW) who have negative or unknown histories of previous varicella infection and who are exposed to persons with active varicella should not work with susceptible patients from the 10th to the 21st day after exposure.   

In general, a history of previous chickenpox or herpes zoster in an adult or child is a reliable indication of immunity. 

Infection confers long immunity, second attacks are rare.  Infection apparently remains latent and may recur years later as shingles (herpes zoster) in a proportion of older adults.

Preventative Measures

Varicella-Zoster immunoglobulin (ZIG) has been developed and should be given to individuals at high risk of developing progressive varicella. 

Significant exposure is usually defined as a household contact, play contact of longer than one hour indoors, classroom contact or other close prolonged exposure.   

ZIG is available from the Red Cross Blood Transfusion Service on a restricted basis.   

ZIG should be given to individuals in the following categories:  

• Patients suffering from diseases associated with cellular immune deficiency (eg, Hodgkin’s disease)
• Those receiving immunosuppressive therapy
• Pregnant women who are susceptible to varicella infection
• Neonates whose mothers are susceptible to varicella infection
• Premature infants born at less than 28 weeks gestation (or less than 1,000g), regardless of maternal history

ZIG is also indicated for neonates whose mother develops chickenpox 7 or fewer days before delivery or up to 7 days after delivery. 

ZIG must be given as early as possible in the incubation period, within 72 hours of exposure if possible.  ZIG is highly efficacious, but is often in short supply.

Normal immunoglobulin (human) can be used for the prevention of varicella if ZIG is unavailable. This does not usually prevent chickenpox, but it lessens the severity of the disease. 

Standard precautions should be practiced at all times. Airborne precautions should be implemented for all patients with known or suspected Chickenpox.   

Patients should be nursed in a single room until lesions are crusted.  Patients with uncomplicated Chickenpox should not be admitted to hospital because they present a hazard to susceptible patients and personnel. 

If an inadvertent exposure in the hospital by an infected patient, health care worker, or visitor occurs the following control measures should be employed: 

• Those personnel and patients who have been exposed and are susceptible to varicella should be identified
• All exposed, susceptible patients should be discharged as soon as possible
• All exposed, susceptible patients who cannot be discharged should be placed in strict isolation from day 8 to day 21 after the onset of the rash in the index patient. For those who have received ZIG or are immunocompromised, this interval should be until day 28
• All susceptible, exposed staff should be either given leave or excused from patient contact from day 8 to day 21 after the onset of the rash in the index case

Notification to the Public Health Unit: Chickenpox or Herpes-Zoster Virus is not a notifiable disease to the Public Health Unit.   

References

Benenson AS, ed, 15th ed. 1990, Control Of Communicable Diseases In Man. American Public Health Association, Washington.

Bennett JV, Brachman PS, Sandford JP, eds, 1992, 3rd edition, Hospital Infections.  Little, Brown and Company, Boston.

Committee on Infectious Diseases, American Academy of Pediatrics, 23rd ed. 1994, Red Book, Report of the Committee on Infectious Diseases, America.

National Health and Medical Research Council, 4th ed. 1991,  The Australian Immunisation Procedures Handbook, Canberra.

National Health and Medical Research Council, 5th ed. 1994, The Australian Immunisation Procedures Handbook, Canberra.

NSW Health Department, 1999, Infection Control Policy, 99/87 AIDS/Infectious Diseases Branch, Sydney.

Reid D, Grist NR, Pinkerton IW, 1986, Infections in Current Medical Practice. Butterworth, London.

Wenzel RP, 1993, 2nd ed, Prevention and Control of Nosocomial Infections, Williams and Wilkins, Baltimore.

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