Varicella is an acute disease caused by the varicella zoster virus (VZV). It is commonly known as chickenpox. Varicella is highly contagious. About 90% of susceptible persons in close contact with an infected person will develop varicella. The virus is spread mainly through infected respiratory secretions, but also can be spread through direct contact or inhalation of the watery fluids in the varicella skin lesions (vesicles).
About 12 days after exposure, a 1 to 2 day prodrome may begin. During the prodrome infected people, especially adults, develop fever and malaise. The prodrome is then followed by a rash. The varicella rash usually begins on the scalp and then moves downward and outward. It covers the trunk and extremities, with most lesions occurring on the trunk. The itchy rash progresses rapidly from macules to papules to vesicles, which then crust over. Infected people usually have 250 to 500 lesions, but can have as few as 10 or more than 1,500. The lesions can occur on the mucous membranes of the mouth and throat, respiratory tract, and the eye, as well as on the skin. The lesions are normally 1 to 4 mm in diameter and occur in successive crops over several days, so all stages of lesions may be present at any given time.
In general, varicella is usually mild and goes away without treatment. The most common complications include secondary bacterial infections of the skin, dehydration, pneumonia, and central nervous system manifestations. Adults, people who are immune compromised, and infants are most likely to experience complications from varicella infection.
Varicella can be prevented or the severity reduced if varicella vaccine is given within 3 to 5 days of exposure. In addition, varicella zoster immune globulin (VariZIG) can help reduce severity if given within 10 days of exposure. VariZIG is mainly used in persons at high risk for complications. Once symptoms develop, varicella illness cannot be prevented. However, several antiviral drugs, such as acyclovir, can reduce length and severity of illness if given within 24 hours of onset of the rash.
There is one varicella vaccine licensed for use in the United
States. There is also a combination vaccine that contains varicella
vaccine and MMR vaccine.
Product: Varivax® (Varicella)
Manufacturer: Merck & Co
Year licensed: 1995
Product: ProQuad® (Measles, Mumps, Rubella, and Varicella)
Manufacturer: Merck & Co
Year licensed: 2005
* Varicella vaccine contains gelatin and neomycin (see package insert).
* When varicella antigen is given in combination with other
antigens (e.g., MMR) in one vaccine, the other antigens in the vaccine
may cause other side effects. For more information about these possible
side effects, go to the MMR pages on the Vaccines section of this
website. Note: The first dose of MMRV vaccine has been associated with
rash and higher rates of fever than MMR and varicella given separately.
Seizures caused by fever are also reported more often after MMRV.
The most common complication is bacterial infection of the skin or other parts of the body, including the bones, lungs, joints, and blood. The virus can also lead to pneumonia or infection of the brain. These complications are rare but serious. Complications are more common in infants, adults, and people with weakened immune systems.
Chickenpox poses a significant threat to immunocompromised people. The best way to prevent infection in each patient is by immunizing susceptible family members and close contacts of the person.