Chicken Pox is the common name for Varicella simplex, classically one of the childhood infectious diseases caught and survived by most children.
Chicken Pox is caused by the varicella-zoster virus. It starts with moderate fever and then characteristic spots appearing in two or three waves, mainly on the body and head rather than the hands and becoming itchy raw pox (pocks), small open sores which heal mostly without scarring.
Chicken Pox has a two-week incubation period and is highly contagious by air transmission two days before symptoms appear. Therefore, Chicken Pox spreads quickly through schools and other places of close contact. Once someone has been infected with the disease, they usually develop protective immunity for life. It is fairly rare to get the Chicken Pox multiple times, but it is possible for people with irregular immune systems. As the disease is more severe if contracted by an adult, parents have been known to ensure their children become infected before adulthood.
The disease can be fatal. Pregnant women and those with immune system depression are more at risk. Death is usually from varicella pneumonia. In the US, 55 percent of Chicken Pox deaths were in the over-20 age group. Pregnant women not known to be immune and who come into contact with Chicken Pox should contact their doctor immediately, as the virus can cause serious problems for the fetus.
A Chicken Pox vaccine has been available since 1995, and is now required in some countries for children to be admitted into elementary school. In addition, effective medications (e.g., aciclovir) are available to treat Chicken Pox in healthy and immunocompromised persons. Calamine lotion is often used to ease itching and paracetamol to reduce fever. Aspirin is not recommended in children with Chicken Pox, as it can lead to Reye’s syndrome.
Chicken Pox is highly infectious infection that spreads from person to person by direct contact or through the air from an infected person’s coughing or sneezing. Touching the fluid from a Chicken Pox blister can also spread the disease. A persons with Chicken Pox is contagious 1-2 days before the rash appears and until all blisters have formed scabs. This may take between 5-10 days. It takes from 10-21 days after contact with an infected person for someone to develop Chicken Pox.
The Chicken Pox blisters start as a small red papule which develops an irregular outline in the shape of a rose petal. A thin-walled, clear vesicle (dew drop) develops on top of the area of redness. This “dew drop on a rose petal” lesion is very characteristic for Chicken Pox. After about 8-12 hours the fluid in the vesicle gets cloudy and the vesicle breaks leaving a crust. The fluid is highly contagious, but once the lesion crusts over, it is not considered contagious. The crust usually falls off after 7 days sometimes leaving a craterlike scar.
Although one lesion goes through this complete cycle in about 7 days, another hallmark of Chicken Pox is the fact that new lesions crop up every day for several days. Therefore, it may take about a week until new lesions stop appearing and existing lesions crust over.
Second infections with Chicken Pox occur in immunocompetent individuals, but are uncommon and rarely severe.
Vaccination Japan was among the first countries to routinely vaccinate for Chicken Pox. Routine vaccination against varicella zoster virus is also performed in the United States, and the incidence of Chicken Pox has been dramatically reduced from 4 million cases per year in the pre-vaccine era to approximately 400,000 cases per year as of 2005.
The vaccine is exceedingly safe: approximately 5% of children who receive the vaccine develop a fever or rash, but there have been no deaths, as of May 2006, attributable to the vaccine despite more than 40 million doses being administered.
41 of the 50 US states require immunization for children attending government-run schools. The vaccination is not routine in the United Kingdom. Debate continues in the UK on the time when it will be desirable to adopt routine Chicken Pox vaccination, and in the US opinions that it should be dropped, individually, or along with all immunizations, are also voiced.
The CDC and corresponding national organisations are carefully observing the failure rate which may be high compared with other modern vaccines – large outbreaks of Chicken Pox having occurred at schools which required their children to be vaccinated.
Catching wild Chicken Pox as a child has been thought to commonly result in lifelong immunity. Parents have deliberately ensured this in the past with pox parties and similarly for some other diseases such as rubella.
Historically, exposure of adults to contagious children has boosted their immunity, reducing the risk of shingles.
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