Chickenpox overview
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Associate Editor(s)-in-Chief:
Aravind Reddy Kothagadi M.B.B.S[2]
Michael Maddaleni, B.S.
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Overview
Chickenpox is the common name for Varicella zoster, and it is classically one of the childhood infectious diseases caught by and survived by almost every child. It is one of the most contagious infectious diseases. The affected child or adult may develop hundreds of itchy, fluid-filled blisters that burst and form crusts. Chickenpox is caused by varicella-zoster, a member of the herpes virus family. The same virus also causes shingles (herpes zoster) in adults.
Historical Perspective
Classification=
Pathophysiology
Causes
Chickenpox is caused by the varicella-zoster virus , also known as human herpes virus 3 (HHV-3), one of the eight herpes viruses known to affect humans.
Transmission
Transmission of the disease from an infected individual occurs by the following ways:
- Droplet transmission of Nasopharyngeal secretions
- Contact with Vesicle Fluid from the Skin Lesions.
Differentiating Chickenpox from other Diseases
There are many active considerations that need to be ruled out to diagnose chickenpox. The one exception to this is Smallpox. Smallpox would be a major concern in the case of biological warfare.
Screening
The main purpose to screen for chickenpox is to be able to treat it early on before a clinical diagnosis can be made. The people that would need to be screened are the patients that do not currently have symptoms but are at high risk for developing chickenpox.
Diagnosis
Physical Examination
The diagnosis of varicella is primarily clinical. In a non-immunized individual with typical prodromal symptoms associated with the appropriate appearing rash occurring in "crops", no further investigation would normally be undertaken.
If further investigation is undertaken, 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 reposnse. Vesicle 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 (IgE).[1]
Prenatal diagnosis of foetal 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.
Laboratory Findings
Varicella (chickenpox) used to be very common in the United States before varicella vaccine became available. Health care providers could readily diagnose varicella by doing a clinical assessment. As a result, testing specimens and getting laboratory confirmation of varicella-zoster virus (VZV) were not usually needed. However, clinical diagnosis is becoming more challenging because fewer people get varicella. Also, varicella in vaccinated people is often mild and atypical in presentation. Therefore, laboratory confirmation of varicella is becoming increasingly important in routine clinical practice.
Chest X Ray
Pneumonia, as a complication of chickenpox, rarely occurs in children, but occurs in about one-fifth of adults. Chest x-ray shows cloudiness throughout the lungs, caused by acute pneumonia following chickenpox.
Treatment
Secondary Prevention
There are several things that can be done at home to help relieve the symptoms and prevent skin infections. Calamine lotion and colloidal oatmeal baths may help relieve some of the itching. Keeping fingernails trimmed short may help prevent skin infections caused by scratching blisters.
References
- ↑ McPherson & Pincus: Henry's Clinical Diagnosis and Management by Laboratory Methods, 21st ed., 2007, Chapter 54.