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Chickenpox
Classification and external resources
Child with varicella disease
ICD-10	B01.
ICD-9	052
DiseasesDB	29118
MedlinePlus	001592
eMedicine	ped/2385 derm/74, emerg/367
MeSH	C02.256.466.175

Chickenpox or chicken pox is a highly contagious illness caused by primary infection with varicella zoster virus (VZV).^[1] It usually starts with vesicular skin rash mainly on the body and head rather than at the periphery and become itchy raw pockmarks which mostly heal without scarring.

Chicken pox is spread easily through coughs or sneezes of ill individuals, or through direct contact with secretions from the rash. Following primary infection there is usually lifelong protective immunity from further episodes of chickenpox.

Chickenpox is rarely fatal, although it is generally more severe in adult males than in adult females or children. Pregnant women and those with a suppressed immune system are at highest risk of serious complications. The most common late complication of chicken pox is shingles, caused by reactivation of the varicella zoster virus decades after the initial episode of chickenpox.

Chickenpox has been observed in nonhuman primates, including chimpanzees^[2] and gorillas.^[3]

[edit] Signs and symptoms

Chickenpox is a highly infectious disease that spreads from person to person by direct contact or by air from an infected person's coughing or sneezing. Touching the fluid blister can also spread the disease. A person with chickenpox is infectious from one to five days before the rash appears.^[4] The contagious period continues until all blisters have formed scabs, which may take 5 to 10 days.^[5] It takes from 10 to 21 days after contact with an infected person for someone to develop chickenpox.^[6]

[edit] Infection in pregnancy and neonates

For pregnant women, antibodies produced as a result of immunization or previous infection are transferred via the placenta to the fetus.^[7] Women who are immune to chickenpox cannot become infected and do not need to be concerned about it for themselves or their infant during pregnancy.^[8]

Varicella infection in pregnant women can lead to viral transmission via the placenta and infection of the fetus. If infection occurs during the first 28 weeks of gestation, this can lead to fetal varicella syndrome (also known as congenital varicella syndrome)^{[citation needed]}. Effects on the fetus can range in severity from underdeveloped 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

Infection late in gestation or immediately following birth is referred to as "neonatal varicella".^[9] Maternal infection is associated with premature delivery. The risk of the baby developing the disease is greatest following exposure to infection in the period 7 days prior to delivery and up to 7 days following the birth. The baby may also be exposed to the virus via infectious siblings or other contacts, but this is of less concern if the mother is immune. Newborns who develop symptoms are at a high risk of pneumonia and other serious complications of the disease.^[10]

[edit] Pathophysiology

Exposure to VZV in a healthy child initiates the production of host immunoglobulin G (IgG), immunoglobulin M (IgM), and immunoglobulin A (IgA) antibodies; IgG antibodies persist for life and confer immunity. Cell-mediated immune responses are also important in limiting the scope and the duration of primary varicella infection. After primary infection, VZV is hypothesized to spread from mucosal and epidermal lesions to local sensory nerves. VZV then remains latent in the dorsal ganglion cells of the sensory nerves. Reactivation of VZV results in the clinically distinct syndrome of herpes zoster (i.e., shingles), and sometimes Ramsay Hunt syndrome type II.

[edit] Diagnosis

Early rash of smallpox vs chickenpox: rash mostly on the torso is characteristic of chickenpox

The diagnosis of varicella is primarily clinical. In a non-immunized individual with typical early nonspecific, or "prodromal", symptoms associated with the appropriate appearing rash occurring in "crops". Confirmation of the diagnosis can be sought through either examination of the fluid within the vesicles, or by testing blood for evidence of an acute immunologic response. Vesicular fluid can be examined with a Tsanck smear, or better with examination for direct fluorescent antibody. The fluid can also be "cultured", whereby attempts are made to grow the virus from a fluid sample. Blood tests can be used to identify a response to acute infection (IgM) or previous infection and subsequent immunity (IgG).^[11]

Prenatal diagnosis of fetal varicella infection can be performed using ultrasound, though a delay of 5 weeks following primary maternal infection is advised. A PCR (DNA) test of the mother's amniotic fluid can also be performed, though the risk of spontaneous abortion due to the amniocentesis procedure is higher than the risk of the baby developing foetal varicella syndrome.^[10]

[edit] Prevention

A varicella vaccine was first developed by Michiaki Takahashi in 1974 derived from the Oka strain. It has been available in the U.S. since 1995 to inoculate against the disease. Some countries require the varicella vaccination or an exemption before entering elementary school. Protection is not lifelong and further vaccination is necessary five years after the initial immunization.^[12]

[edit] Treatment

This section requires expansion.

Although there have been no formal clinical studies evaluating the effectiveness of topical application of calamine lotion, a topical barrier preparation containing zinc oxide and one of the most commonly used interventions, it has an excellent safety profile.^[13] It is important to maintain good hygiene and daily cleaning of skin with warm water to avoid secondary bacterial infection.^[14] Scratching may also increase the risk of secondary infection.^[15] Addition of a small quantity of vinegar to the water is sometimes advocated. Pain killers could be taken to prevent feeling itchy ^[16]

To relieve the symptoms of chicken pox, people commonly use anti-itching creams and lotions. A very effective cream to use is hydrocortisone. These lotions are not to be used on the face or close to the eyes. An oatmeal bath also might help ease discomfort.^[17]

[edit] Children

If oral acyclovir is started within 24 hours of rash onset it decreases symptoms by one day but has no effect on complication rates. Use of acyclovir therefore is not currently recommended for immunocompetent individuals (i.e., otherwise healthy persons without known immunodeficiency or those on immunosuppressive medication).^[18]

[edit] Adults

Infection in otherwise healthy adults tends to be more severe and active; treatment with antiviral drugs (e.g. acyclovir) is generally advised, as long as it is started within 24–48 hours from rash onset.^[19] 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, even though they are a tiny fraction of the cases.^{[citation needed]}

A 16-year-old's back during chickenpox.

[edit] Prognosis

The duration of the visible blistering caused by varicella zoster virus varies in children usually from 4 to 7 days, and the appearance of new blisters begins to subside after the 5th day. Chickenpox infection is milder in young children, and symptomatic treatment, with sodium bicarbonate baths or antihistamine medication may ease itching.^[20] Paracetamol (acetaminophen) is widely used to reduce fever. Aspirin, or products containing aspirin, must not be given to children with chickenpox as this risks causing Reye's Syndrome.^[21]

In adults, the disease is more severe, though the incidence is much less common. Infection in adults is associated with greater morbidity and mortality due to pneumonia, hepatitis, and encephalitis. In particular, up to 10% of pregnant women with chickenpox develop pneumonia, the severity of which increases with onset later in gestation. In England and Wales, 75% of deaths due to chickenpox are in adults.^[10] Inflammation of the brain, or encephalitis, can occur in immunocompromised individuals, although the risk is higher with herpes zoster.^[22] Necrotizing fasciitis is also a rare complication.^[23]

Secondary bacterial infection of skin lesions, manifesting as impetigo, cellulitis, and erysipelas, is the most common complication in healthy children. Disseminated primary varicella infection, usually seen in the immunocompromised or adult populations, may have high morbidity. Ninety percent of cases of varicella pneumonia occur in the adult population. Rarer complications of disseminated chickenpox also include myocarditis, hepatitis, and glomerulonephritis.^[24]

Hemorrhagic complications are more common in the immunocompromised or immunosuppressed populations, although healthy children and adults have been affected. Five major clinical syndromes have been described: febrile purpura, malignant chickenpox with purpura, postinfectious purpura, purpura fulminans, and anaphylactoid purpura. These syndromes have variable courses, with febrile purpura being the most benign of the syndromes and having an uncomplicated outcome. In contrast, malignant chickenpox with purpura is a grave clinical condition that has a mortality rate of greater than 70%. The etiology of these hemorrhagic chickenpox syndromes is not known.^[24]

[edit] Epidemiology

Primary varicella is an endemic disease. Cases of varicella are seen throughout the year but more commonly in winter and early spring. Varicella is one of the classic diseases of childhood, with the highest prevalence in the 4–10 year old age group. Like rubella, it is uncommon in preschool children. Varicella is highly communicable, with an infection rate of 90% in close contacts. Most people become infected before adulthood but 10% of young adults remain susceptible.

Historically, varicella has been a disease predominantly affecting preschool and school-aged children. In adults the pock marks are darker and the scars more prominent than in children.^[25]

[edit] History

Chickenpox was first identified by Persian scientist Muhammad ibn Zakariya ar-Razi (865–925), known to the West as "Rhazes", who clearly distinguished it from smallpox and measles.^[26] Giovanni Filippo (1510–1580) of Palermo later provided a more detailed 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".

• Shingles

[edit] References

[edit] Further reading

• Bernstein, Henry. "Who Discovered Chickenpox?". Pediatrics Questions and Answers. Family Education Network. http://www.familyeducation.com/experts/advice/0,1183,25-26758,00.html. Retrieved 2005-10-16. 
• "Chickenpox (Varicella) Vaccine". Immunization Action Coalition. October 2005. http://www.vaccineinformation.org/varicel/qandavax.asp. Retrieved 2006-06-12. 
• Centers for Disease Control and Prevention (CDC) (2005). "Varicella-related deaths--United States, January 2003-June 2004" (PDF). MMWR Morb Mortal Wkly Rep 54 (11): 272–4. PMID 15788992. http://www.cdc.gov/mmwr/PDF/wk/mm5411.pdf. 
• Thomas S, Wheeler J, Hall A (2002). "Contacts with varicella or with children and protection against herpes zoster in adults: a case-control study" (PDF). Lancet 360 (9334): 678–82. doi:10.1016/S0140-6736(02)09837-9. PMID 12241874. http://image.thelancet.com/extras/01art6088web.pdf. 
• Jeff Aronson (2000). "When I Use a Word...Chickenpox" (web). BMJ 321 (7262): 682. doi:10.1136/bmj.321.7262.682. PMID 10987775. http://www.bmj.com/cgi/content/full/321/7262/682. 

http://www.nhs.uk/conditions/chickenpox/Pages/Introduction.aspx?url=Pages/what-is-it.aspx http://kidshealth.org/kid/ill_injure/sick/chicken_pox.html http://www.netdoctor.co.uk/diseases/facts/chickenpox.htm http://hcd2.bupa.co.uk/fact_sheets/html/chickenpox.html http://www.patient.co.uk/health/Chickenpox-in-Children-Under-12.htm

[edit] External links

Wikimedia Commons has media related to: Chickenpox

• "Varicella Disease (Chickenpox): Varicella, although a common disease, can be dangerous and even deadly.". CDC. 2005-05-26. http://www.cdc.gov/vaccines/vpd-vac/varicella/default.htm. 
• "Chicken pox during pregnancy". BabyCenter. 2005-12-01. http://www.babycenter.com/0_chicken-pox-during-pregnancy_9329.bc.