Varicella-zoster virus (VZV) causes chickenpox which usually mild, but may be severe in infants, adults, and people with impaired immune systems. Almost everyone gets chickenpox before the age of 20.
Chickenpox is highly contagious. The virus spreads from person to person by direct contact, or through the air. There is a high chance (around 90%) of contracting chickenpox if exposed to an infected family member.
The characteristics of chickenpox is having an itchy rash, which then 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 only a few lesions to more than 500 lesions on his or her body during an attack. The averge is 300-400 lesions though.
Adults are more likely to have a more serious case of chickenpox with a higher rate of complications and death.
Chickenpox is contagious 1-2 days before the rash appears and until all blisters have formed scabs. Chickenpox develops within 10-21 days after contact with an infected person.
Varicella vaccine has been available since March 1995 and is approved for use in healthy children 12 months of age or older, and susceptible (i.e., no evidence of having had chickenpox in the past) adolescents and adults.
Varicella vaccine is highly effective in protecting against severe chickenpox. Cases of disease caused by the wild virus, which may occur in a small proportion of vaccinees, are typically very mild, with fewer than 50 skin lesions and no fever.
It is recommended that all children be routinely vaccinated at 12-18 months of age and that all susceptible children receive the vaccine before their 13th birthday. Many states in the USA require vaccination for entry into pre-school or public school beginning in 1999. The vaccine is also approved for susceptible adolescents and adults, especially those with close contact with persons at high risk for serious complications (e.g., health-care workers, family contacts of immunocompromised persons).
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 immunocompromised persons (e.g, those with cancer, human immunodeficiency virus/AIDS; those receiving medications that depress the immune system).
Varicella zoster immune globulin (VZIG), an immune globulin made from plasma of healthy volunteer blood donors with high levels of antibody to VZV, is recommended after exposure for persons at high risk for complications (e.g., immunocompromised persons, pregnant women, premature infants)
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