Tuesday, 26 November 2013

Chicken Pox


Chicken pox
Chickenpox or chicken pox is a  illness caused by primary infections  with varicella zoster virus (VZV). 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.
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 from one to five days before the rash appears. The contagious period continues for 4 to 5 days after the appearance of the rash, or until all lesions have crusted over. Immunocompromised patients are probably contagious during the entire period new lesions keep appearing. Crusted lesions are not contagious.
It takes from 10 to 21 days after contact with an infected person for someone to develop chickenpox.
Symptoms:-
 myalgia, nausea, fever, headache, sore throat, pain in both ears, complaints of pressure in head or swollen face, and malaise in adolescents and adults. In children, the first symptom is usually the development of a popular rash, followed by development of malaise, fever (a body temperature of 38 °C (100 °F), but may be as high as 42 °C (108 °F) in rare cases), and anorexia. 
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.
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
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.
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.
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.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.
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). 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, microcephalyhydrocephalyaplasia of brain
§  Damage to the eye: optic stalkoptic cup, and lens vesiclesmicrophthalmiacataractschorioretinitisoptic 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
Treatment:-
In most cases, it is enough to keep children comfortable while their own bodies fight the illness. Oatmeal baths in lukewarm water provide a crusty, comforting coating on the skin. An oral antihistamine can help to ease the itching, as can topical lotions. Trim the fingernails short to reduce secondary infections and scarring.
Safe antiviral medicines have been developed. To work well, they usually must be started within the first 24 hours of the rash.
·         For most otherwise healthy children without severe symptoms, antiviral medications are usually not used. Adults and teens, who are at risk for more severe symptoms, may benefit if the case is seen early in its course.
·         For those with skin conditions (such as eczema or recent sunburn), lung conditions (such as asthma), or those who have recently taken steroids, the antiviral medicines may be very important. The same is also true for adolescents and children who must take aspirin on an ongoing basis.
·         Some doctors also give antiviral medicines to people in the same household who subsequently come down with chickenpox. Because of their increased exposure, they would normally experience a more severe case of chickenpox.
DO NOT GIVE ASPIRIN to someone who may have chickenpox. Use of aspirin has been associated with a serious condition calledReyes Syndrome. Ibuprofen has been associated with more severe secondary infections. Acetaminophen may be used.
Until all chickenpox sores have crusted over or dried out, avoid playing with other children, going back to school, or returning to work.


Complication:-
·         Women who get chickenpox during pregnancy are at risk for congenital infection of the fetus.
·         Newborns are at risk for severe infection, if they are exposed and their mothers are not immune.
·         A secondary infection of the blisters may occur.
·         Encephalitis is a serious, but rare complication.
·         Reye's syndrome, pneumonia, myocarditis, and transient arthritis are other possible complications of chickenpox.
·         Cerebellar ataxia may appear during the recovery phase or later. This is characterized by a very unsteady walk.