Chickenpox

Chickenpox
Other names	varicella
A boy presenting with the characteristic blisters of chickenpox
Specialty	Infectious disease
Symptoms	Small, itchy blisters, headache, loss of appetite, tiredness, fever[1]
Usual onset	10–21 days after exposure[2]
Duration	5–10 days[1]
Causes	Varicella zoster virus[3]
Prevention	Varicella vaccine[4]
Medication	Calamine lotion, paracetamol (acetaminophen), aciclovir[5]
Deaths	6,400 per year (with shingles)[6]

Chickenpox, or chicken pox, also known as varicella,^{[pronunciation?]} is a highly contagious, vaccine-preventable disease caused by the initial infection with varicella zoster virus (VZV), a member of the herpesvirus family.^[3][5] The disease results in a characteristic skin rash that forms small, itchy blisters, which eventually scab over.^[1] It usually starts on the chest, back, and face.^[1] It then spreads to the rest of the body.^[1] The rash and other symptoms, such as fever, tiredness, and headaches, usually last five to seven days.^[1] Complications may occasionally include pneumonia, inflammation of the brain, and bacterial skin infections.^[7] The disease is usually more severe in adults than in children.^[8]

Chickenpox is an airborne disease which easily spreads via human-to-human transmission, typically through the coughs and sneezes of an infected person.^[5] The incubation period is 10–21 days, after which the characteristic rash appears.^[2] It may be spread from one to two days before the rash appears until all lesions have crusted over.^[5] It may also spread through contact with the blisters.^[5] Those with shingles may spread chickenpox to those who are not immune through contact with the blisters.^[5] The disease can usually be diagnosed based on the presenting symptom;^[9] however, in unusual cases it may be confirmed by polymerase chain reaction (PCR) testing of the blister fluid or scabs.^[8] Testing for antibodies may be done to determine if a person is immune.^[8] People usually only get chickenpox once.^[5] Although reinfections by the virus occur, these reinfections usually do not cause any symptoms.^[10]

Since its introduction in 1995 in the United States, the varicella vaccine has resulted in a decrease in the number of cases and complications from the disease.^[4] It protects about 70–90 percent of people from disease with a greater benefit for severe disease.^[8] Routine immunization of children is recommended in many countries.^[11] Immunization within three days of exposure may improve outcomes in children.^[12] Treatment of those infected may include calamine lotion to help with itching, keeping the fingernails short to decrease injury from scratching, and the use of paracetamol (acetaminophen) to help with fevers.^[5] For those at increased risk of complications, antiviral medication such as aciclovir is recommended.^[5]

Chickenpox occurs in all parts of the world.^[8] In 2013, there were 140 million cases of chickenpox and shingles worldwide.^[13] Before routine immunization the number of cases occurring each year was similar to the number of people born.^[8] Since immunization the number of infections in the United States has decreased nearly 90%.^[8] In 2015 chickenpox resulted in 6,400 deaths globally – down from 8,900 in 1990.^[6][14] Death occurs in about 1 per 60,000 cases.^[8] Chickenpox was not separated from smallpox until the late 19th century.^[8] In 1888 its connection to shingles was determined.^[8] The first documented use of the term chicken pox was in 1658.^[15] Various explanations have been suggested for the use of "chicken" in the name, one being the relative mildness of the disease.^[15]