Chicken Pox Varicella-zoster

Varicella-zoster, also commonly known as chicken pox, is a highly contagious skin disease caused by the varicella-zoster virus, a member of the herpes virus family. Infection with this virus is often considered as a “nuisance” and uncomfortable disease of childhood. 

People of all ages can contract varicella; however, the disease occurs more often in children, with most people contracting varicella by the age of 15. The disease is usually more severe in adults.

Most people acquire lifetime immunity to varicella after they have recovered from a first infection. In otherwise healthy persons, clinical illness after reexposure is rare. The virus can sometimes reappear later in life in the form of a disease called shingles (also known as herpes zoster, or simply zoster).

Varicella is usually a mild disease in children, lasting 4 to 7 days. The period of contagiousness of infected persons is estimated to begin 1 to 2 days before the onset of rash and to end when all the sores are crusted, typically 4 to 7 days after onset of rash. Symptoms of varicella include: mild fever up to 102 degrees F; weakness; and an itchy rash which generally begins on the scalp, then includes the trunk, and finally the arms and legs. The varicella rash develops in crops with red bumps that progress to blisters which then burst and create open sores before scabbing over. Complications of varicella can include: bacterial skin infection which can cause scarring, particularly when the patient continually scratches their sores; cerebellar ataxia (loss of coordination of muscle movements); encephalitis (inflammation of the brain); nerve palsies (damaged nerves); Reye's syndrome (a severe combination of liver and brain disease that is associated with taking aspirin).

Other serious complications can occur in patients with AIDS, lupus, leukemia, and cancer, or in those taking immune-suppressing drugs. Newborn infants whose mothers contract varicella in the last trimester of pregnancy can be affected by the disease. If the mother develops varicella from five days before delivery to two days after, the baby's fatality rate increases significantly.

Breakthrough varicella is a modified version of the disease that can occur in some vaccinated persons, as the vaccine is only 70 - 90 percent effective in preventing the disease. Breakthrough varicella usually presents with a milder rash, less fever, and shorter duration. Mild, breakthrough varicella is still infectious, and persons suspected of having the disease should be isolated. 

After the initial infection is over, the virus still remains dormant in sensory nerves where it might be reactivated at a later time, causing a different illness called herpes zoster or shingles. This is a very painful rash that typically appears n the skin of the chest or abdomen along the distribution of the sensory nerves under the skin. 

Treatment for varicella is mainly to relieve symptoms. Acetaminophen is used to decrease fever and aches in the initial stages of the disease. Aspirin should never be given to children due to the risk of developing Reye's syndrome. The severe itching from the rash can be decreased with oatmeal baths and over-the-counter lotions and moisturisers, such as calamine lotion. Itching can also be controlled with Benadryl or other antihistamines. Minimizing scratching will help to diminish the risk of bacterial infection associated with varicella.

Acyclovir, an antiviral medication, is sometimes prescribed to patients with pre-existing medical conditions that put them at risk for severe disease (such as those with severe skin diseases or immunodeficiency). 

Chicken pox occurs worldwide. Some countries have vaccination programs against varicella that have decreased the risk of exposure. These countries include the United States, Australia, Canada, Costa Rica, Dominican Republic, Germany, Mexico, Qatar, Spain, South Korea, Switzerland, United Arab Emirates, and Uruguay.