Chickenpox

Chickenpox

Child with varicella disease
ICD-10	B01
ICD-O:
ICD-9	052
OMIM	[1]
MedlinePlus	001592
eMedicine	ped/2385
DiseasesDB	29118

Chickenpox (or chicken pox), also known as varicella, is a common and very highly contagious viral disease caused by the varicella-zoster virus (VSZ). It is classically one of the childhood infectious diseases caught and survived by almost every child, although currently there is a vaccine.

Following primary infection, there is usually lifelong protective immunity from further episodes of chickenpox. Recurrent chickenpox, commonly known as shingles, is fairly rare but more likely in people with compromised immune systems.

Varicella-zoster virus and overview

Chickenpox is caused by the varicella-zoster virus (VZV), also known as human herpes virus 3 (HHV-3), one of the eight herpes viruses known to affect humans.

The Varicella zoster virus (VZV), the causal agent of chickenpox, is one of the eight herpes viruses known to affect humans (and other vertebrates). Multiple names are used to refer to same virus, creating some confusion. Varicella virus, zoster virus, human herpes 3 (HHV-3), and Varicella Zoster Virus (VZV) all refer to the same viral pathogen.

VZV is closely related to the herpes simplex viruses (HSV), sharing much genome homology. The known envelope glycoproteins (gB, gC, gE, gH, gI, gK, gL) correspond with those in HSV, however there is no equivalent of HSV gD. VZV virons are spherical and 150-200 nm in diameter. Their lipid envelope encloses the nucleocapsid of 162 capsomeres arranged in a hexagonal form. Its DNA is a single, linear, double-stranded molecule, 125,000 nt long.

The virus is very susceptible to disinfectants, notably sodium hypochlorite. Within the body it can be treated by a number of drugs and therapeutic agents including aciclovir, zoster-immune globulin (ZIG), and vidarabine.

The initial infection with the varicella-zoster virus (the primary VZV infection) results in chickenpox (varicella), which may rarely result in complications including VZV encephalitis or pneumonia. Even when clinical symptoms of varicella have resolved, VZV remains dormant in the nervous system of the host in the trigeminal and dorsal root ganglia.

In about 10-20% of cases, VZV reactivates later in life producing a disease known as shingles, herpes zoster, or simply zoster. These localized eruptions occur particularly in people with compromized immune systems, such as the elderly, and perhaps even those suffering sunburn. Serious complications of shingles include post-herpetic neuralgia, zoster multiplex, myelitis, herpes ophthalmicus, or zoster sine herpete.

Chickenpox starts with conjunctival and catarrhal symptoms 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.

Chickenpox has a 10-14 day incubation period and is highly contagious through physical contact two days before symptoms appear.

Chickenpox is rarely fatal (usually from varicella pneumonia), with pregnant women and those with a suppressed immune systems being more at risk. Pregnant women not known to be immune and who come into contact with chickenpox may need urgent treatment as the virus can cause serious problems for the baby. This is less of an issue after 20 weeks.

Signs and Symptoms

Chickenpox is a highly contagious disease 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 chickenpox blister can also spread the disease. A person with chickenpox is contagious from 1-2 days before the rash appears until all blisters have formed scabs. This may take 5-10 days. It takes from 10-21 days after contact with an infected person for someone to develop chickenpox.

The chickenpox lesions (blisters) start as a 2–4 mm red papule which develops an irregular outline (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 chickenpox. 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 crater-like scar. Although one lesion goes through this complete cycle in about 7 days, another hallmark of chickenpox 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. Children are not to be sent back to school until all lesions have crusted over.

Second infections with chickenpox occur in immunocompetent individuals, but are uncommon. Such second infections are rarely severe. A soundly-based conjecture being carefully assessed in countries with low prevalence of chickenpox due to immunisation, low birth rates, and increased separation is that immunity has been reinforced by subclinical challenges and this is now less common. This is more dangerous with shingles. There have been reported cases of repeat infections.Chickenpox is highly contagious and is spread through the air when infected people cough or sneeze, or through physical contact with fluid from lesions on the skin. Zoster, also known as shingles, is a reactivation of chickenpox and may also be a source of the virus for susceptible children and adults. It is not necessary to have physical contact with the infected person for the disease to spread. Those infected can spread chickenpox before they know they have the disease - even before any rash develops. In fact, people with chickenpox can infect others from about 2 days before the rash develops until all the sores have crusted over, usually 4-5 days after the rash starts.

Congenital defects in babies

These may occur if the child's mother was exposed to VZV during pregnancy. Effects on the fetus may be minimal in nature but physical deformities range in severity from under developed toes and fingers, to severe anal and bladder malformation. Possible problems include:

• Damage to brain: encephalitis, microcephaly, hydrocephaly, aplasia of brain
• Damage to the eye (optic stalk, optic cap, and lens vesicles), microphthalmia, cataracts, chorioretinitis, optic atrophy.
• Other neurological disorder: damage to cervical and lumbosacral spinal cord, motor/sensory deficits, absent deep tendon reflexes, anisocoria/Horner's syndrome
• Damage to body: hypoplasia of upper/lower extremities, anal and bladder sphincter dysfunction
• Skin disorders: (cicatricial) skin lesions, hypopigmentation

Prognosis and treatment

Chickenpox infection tends to be milder the younger a child is and symptomatic treatment, with a little sodium bicarbonate in baths or antihistamine medication to ease itching, and paracetamol (acetaminophen) to reduce fever, are widely used. Ibuprofen can also be used on advice of a doctor. There is no evidence to support the topical application of calamine lotion, a topical barrier preparation containing zinc oxide in spite of its wide usage and excellent safety profile..

It is important to maintain good hygiene and daily cleaning of skin with warm water to avoid secondary bacterial infection. Infection in otherwise healthy adults tends to be more severe and active; treatment with antiviral drugs (e.g. acyclovir) is generally advised. Patients of any age with depressed immune systems or extensive eczema are at risk of more severe disease and should also be treated with antiviral medication. In the U.S., 55 percent of chickenpox deaths are in the over-20 age group.

Vaccination

A varicella vaccine has been available since 1995 to inoculate against the disease. Some countries require the varicella vaccination or an exemption for matriculation in elementary school. Protection is not lifelong and further vaccination is necessary five years after the initial immunization.

In the UK, varicella antibodies are measured as part of the routine of prenatal care, and by 2005 all NHS healthcare personnel had determined their immunity and been immunised if they were non-immune and have direct patient contact. Population-based immunization against varicella is not otherwise practiced in the UK, because of lack of evidence of lasting efficacy or public health benefit.

History

One history of medicine book credits Giovanni Filippo (1510–1580) of Palermo with the first description of varicella (chickenpox). Subsequently in the 1600s, an English physician named Richard Morton described what he thought a mild form of smallpox as "chicken pox." Later, in 1767, a physician named William Heberden, also from England, was the first physician to clearly demonstrate that chickenpox was different from smallpox. However, it is believed the name chickenpox was commonly used in earlier centuries before doctors identified the disease.

There are many explanations offered for the origin of the name chickenpox:

• Samuel Johnson suggested that the disease was "no very great danger", thus a "chicken" version of the pox;
• the specks that appear looked as though the skin was pecked by chickens;
• the disease was named after chick peas, from a supposed similarity in size of the seed to the lesions;
• the term reflects a corruption of the Old English word giccin, which meant itching.

As "pox" also means curse, in medieval times some believed it was a plague brought on to curse children by the use of black magic.

From ancient times, neem has been used by Indians to alleviate the external symptoms of itching and to minimise scarring. Neem baths (neem leaves and a dash of turmeric powder in water) are commonly given for the duration.

During the medieval era, oatmeal was discovered to soothe the sores, and oatmeal baths are today still commonly given to relieve itching.

References

ISBN links support NWE through referral fees

• Krapp, Kristine M., and Jeffrey Wilson. 2005. The Gale encyclopedia of children's health: infancy through adolescence. Detroit: Thomson Gale. ISBN 0787692417.

• Longe, J. L. 2005. The Gale Encyclopedia of Alternative Medicine. Farmington Hills, Mich: Thomson/Gale. ISBN 0787693960.

• Longe, J. L. 2006. The Gale Encyclopedia of Medicine. Detroit: Thomson Gale. ISBN 1414403682.

• Bernstein, Henry. Who Discovered Chickenpox?. Pediatrics Questions and Answers. Family Education Network. Retrieved 2005-10-16.
• Chickenpox (Varicella) Vaccine. Immunization Action Coalition (October 2005). Retrieved 2006-06-12.
• U.S. Census Bureau. Countries Ranked by Popn: 2006. International Data Base. Retrieved 2005-10-16.
• Centers for Disease Control and Prevention (CDC) (2005). Varicella-related deaths—United States, January 2003-June 2004.. MMWR Morb Mortal Wkly Rep 54 (11): 272-4. PMID 15788992.
• Thomas S, Wheeler J, Hall A (2002). Contacts with varicella or with children and protection against herpes zoster in adults: a case-control study.. Lancet 360 (9334): 678-82. PMID 12241874.
• Jeff Aronson (2000). When I Use a Word...Chickenpox. BMJ 321 (7262).

External links

Wikimedia Commons has media related to:

Chickenpox

• Varicella Disease (Chickenpox): Varicella, although a common disease, can be dangerous and even deadly.. CDC (May 26, 2005).
• How to tell you Have Chickenpox

Credits

New World Encyclopedia writers and editors rewrote and completed the Wikipedia article in accordance with New World Encyclopedia standards. This article abides by terms of the Creative Commons CC-by-sa 3.0 License (CC-by-sa), which may be used and disseminated with proper attribution. Credit is due under the terms of this license that can reference both the New World Encyclopedia contributors and the selfless volunteer contributors of the Wikimedia Foundation. To cite this article click here for a list of acceptable citing formats.The history of earlier contributions by wikipedians is accessible to researchers here:

• Chickenpox  ^history
• Varicella_zoster_virus  ^history

The history of this article since it was imported to New World Encyclopedia:

• History of "Chickenpox"

Note: Some restrictions may apply to use of individual images which are separately licensed.