02-06-2012, 02:06 PM
Chickenpox
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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 becomes itchy, raw pockmarks, which mostly heal without scarring. On examination, the observer typically finds lesions at various stages of healing.
Chickenpox is an airborne disease spread easily through coughing or sneezing of ill individuals or through direct contact with secretions from the rash. A person with chickenpox is infectious one to two days before the rash appears.[2] They remain contagious until all lesions have crusted over (this takes approximately six days)[3]. Immunocompromised patients are contagious during the entire period as new lesions keep appearing. Crusted lesions are not contagious.[4]
Diagnosis
The diagnosis of varicella is primarily clinical, with typical early "prodromal" symptoms, and then the characteristic rash. Confirmation of the diagnosis can be sought through either examination of the fluid within the vesicles of the rash, 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).[9]
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 fetal varicella syndrome.[10]
Epidemiology
Primary varicella is a disease that is endemic to all countries worldwide. Varicella has a prevalence that is stable from generation to generation.[11]
In temperate countries, chickenpox is primarily a disease of children, with most cases occurring during the winter and spring, most likely due to school contact. It 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. In temperate countries, most people become infected before adulthood but 10% of young adults remain susceptible.
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.[14] 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.[15]
Varicella infection in pregnant women could 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).[16] Effects on the fetus can range in severity from underdeveloped toes and fingers to severe anal and bladder malformation. Possible problems include:
Shingles
Main article: Herpes zoster
After a chickenpox infection, the virus remains dormant in the body's nerve tissues. The immune system keeps the virus at bay, but later in life, usually as an adult, it can be reactivated and cause a different form of the viral infection called shingles (scientifically known as herpes zoster).[19]
Many adults who have had chicken pox as children are susceptible to shingles as adults, often with the accompanying condition postherpetic neuralgia, a painful condition that make it difficult to sleep. Even after the shingles rash has gone away, there can be night pain in the area affected by the rash.[20]
Shingles affect one in three adults, especially those who are immune suppressed, particularly from cancer, HIV, or other conditions. However, stress can bring on shingles as well, although scientists are still researching the connection. [21]
A shingles vaccine is available for adults over 50 for both adults who had childhood chickenpox or who previously had shingles. [22] The vaccine for shingles lessens the impact of shingles and its side effects.