Also called chickenpox, varicella is a common, acute, and highly contagious infection caused by the herpesvirus varicella-zoster (V-Z), the same virus that, in its latent stage, causes herpes zoster (shingles). It can occur at any age, but it's most common in 2- to 8-year-olds.
Varicella vaccine is effective in preventing chickenpox in up to 90% of recipients. The American Academy of Pediatrics recommends the vaccine for all children and for adolescents and adults who haven't had chickenpox. It is unknown how the vaccine affects shingles.
The viral infection is transferred from one person to another through direct contact with the broken chickenpox blisters and through airborne droplets.
This disease occurs worldwide and is endemic in large cities. Outbreaks occur sporadically, usually in areas with large groups of susceptible children. It affects all races and both sexes equally. Seasonal distribution varies; in temperate areas, incidence is higher during late autumn, winter, and spring.
Signs and symptoms
In children, chickenpox usually begins as an itchy rash of red papules (small bumps) progressing to vesicles (blisters) on the stomach, back and face, and then spreading to other parts of the body. The spread pattern can vary from person to person. Also, depending on the individual case, there may be only a scattering of vesicles or the entire body may be covered with between 250 to 500 vesicles. The vesicles tend to be very itchy and uncomfortable. Some children may also experience additional symptoms such as high fever, headache, cold like symptoms and vomiting and diarrhea. Most adults who get chickenpox experience prodromal symptoms for up to 48 hours before breaking out in rash. These include fever, malaise, headache, loss of appetite and abdominal pain. The condition is usually more severe in adults and can be life-threatening in complicated cases.
Severe pruritus with this rash may provoke persistent scratching, which can lead to infection, scarring, impetigo, furuncles, and cellulitis. Rare complications include pneumonia, myocarditis, fulminating encephalitis (Reye's syndrome), bleeding disorders, arthritis, nephritis, hepatitis, and acute myositis.
DiagnosisChickenpox is diagnosed by characteristic clinical signs and usually doesn't require laboratory tests. However, the virus can be isolated from vesicular fluid within the first 3 to 4 days of the rash; Giemsa stain distinguishes V-Z from vaccinia-variola viruses. Serum contains antibodies 7 days after onset.
Patients must remain in strict isolation until all the vesicles and most of the scabs disappear (usually for 1 week after the onset of the rash). Children can go back to school, however, if just a few scabs remain because, at this stage, chickenpox is no longer contagious. Congenital chickenpox requires no isolation.
Generally, treatment consists of the following:
Salicylates are contraindicated because of their link with Reye's syndrome.
Susceptible patients may need special treatment. When given up to 72 hours after exposure to varicella, varicella-zoster immune globulin may provide passive immunity. Acyclovir may slow vesicle formation, speed skin healing, and control the systemic spread of infection.
How to avoid spread of chickenpox
A person with chickenpox is contagious 1-2 days before the rash appears and until all the blisters have formed scabs. This may take between 5-10 days. Children should stay away from school or childcare facilities throughout this contagious period. Adults with chickenpox who work amongst children, should also remain home.
It can take from 10-21 days after contact with an infected person for someone to develop chickenpox. This is how long it takes for the virus to replicate and come out in the characteristic rash in the new host.
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