Public Health

What is chickenpox? Chickenpox is caused by the varicella-zoster virus and is usually mild, but may be severe in infants, adults, pregnant women, and immuno-compromised individuals. Almost everyone gets chickenpox by adulthood (more than 95% of Americans). The greatest number of cases of chickenpox occur in the late winter and spring.

How is chickenpox spead? Chickenpox is highly contagious (CDC estimates that 4 million cases occur each year) and is spread from person to person by direct contact or through the air. Approximately 90% of persons in a household who have not had chickenpox will get it if exposed to an infected family member.

What are the symptoms of chickenpox?
Chickenpox has a characteristic itchy rash, which forms blisters that dry and become scabs in 4-5 days. The rash may be the first sign of illness, sometimes coupled with fever and general malaise which is usually more severe in adults. An infected person may have anywhere from a few to more than 500 lesions on their body during an attack (average 300-400). Adults are more likely to have a more serious case of chickenpox with a higher rate of complications. Chickenpox is contagious 1-2 days before the rash appears and continues until all blisters have formed scabs. Chickenpox develops within 10-21 days after contact with an infected person.

How severe is chickenpox? Every year there are approximately 5,000-9,000 hospitalizations and l00 deaths from chickenpox in the United States. In the U.S., the annual cost of caring for children of normal health who contract chickenpox was estimated as $918 million in 1993. Pregnant women and immuno-compromised individuals should immediately contact their healthcare provider if they are exposed to an individual with chickenpox.

Is there a chickenpox vaccine? Varicella vaccine has been available since March 1995. It is approved for use in healthy children 12 months of age or older and for susceptible (i.e., no evidence of having had chickenpox in the past) adolescents and adults, especially those in close contact with persons at high-risk for serious complications (e.g., health-care workers, family contacts of immuno-compromised persons, pregnant women). Varicella vaccine is highly effective in protecting against severe chickenpox. Cases of disease due to the wild virus, that may occur in a small proportion of vaccinated people, are typically very mild with fewer than 50 skin lesions and no fever. More than 6 million doses of varicella vaccine have been given since 1995.

Is anyone immune to chickenpox? A history of chickenpox is considered adequate evidence of immunity. A blood test is available to test immunity in persons who are uncertain of their history or who have not had chickenpox. Many of these persons will find that they are immune when tested and thus will not need to be vaccinated. Effective medications (e.g., acyclovir) are available to treat chickenpox in healthy and immuno-compromised persons (e.g., those with cancers, HN/AIDS).

Wyoming Department of Health
2300 Capitol Ave. Cheyenne WY 82002
(307) 777- 7172

(Photo courtesy of the American Academy of Pediatrics, Pennsylvania Chapter)