Chickenpox overview
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Associate Editor(s)-in-Chief:
Michael Maddaleni, B.S.
Aravind Reddy Kothagadi M.B.B.S[2]
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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
Chickenpox was first described by Razi, an Iranian physician. In mid 1500s Giovanni Filippo, described it in more detail. The live attenuated vaccine for Chickenpox was introduced in 1974.
Classification
There is no established classification system for Chickenpox.
Pathophysiology
Chickenpox is a highly contagious disease contracted by the inhalation of aerosolized nasopharyngeal secretions droplets or through direct contact with the vesicles from an infected host.
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 droplet transmission of nasopharyngeal secretions and 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.
Epidemiology and Demographics
- Varicella is an endemic disease spread mainly by the respiratory route
- Cases are observed all through the year but most in the winter and early spring.
- In tropical regions, cases of varicella infection have been reported to be more commonly among adults than children.
Risk Factors
Risk factors which increase the likelihood of contracting Chickenpox are as follows:
- People without a history of chickenpox in the past.
- Not immunized against chickenpox.
- Newborns, especially those born prematurely, less than 1 month or born to mothers who never contracted chickenpox prior to pregnancy'
- Immunocompromised individuals.
- Cancer patients.
- Use of immunosuppressant drugs.
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.
Natural History, Complications and Prognosis
Primary varicella is a common childhood disease in Western countries, which presents as pruritic macules, papules, vesicles, pustules, and crusts, usually on the back, chest, face, and abdomen. Anyone who has recovered from chickenpox may develop shingles; even children can get shingles. Two of the most common complications associated with chickenpox are, Bacterial infections of the skin and soft tissues in children Pneumonia in adults 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.
Diagnosis
History and Symptoms
- Patient with chickenpox presents with the characteristic rash and numerous spread out of lesions.
- Symptoms usually starts as low-grade fever and skin manifestations appear by 1-2 days. Rash initially appears on the head, trunk and then spreads to the rest of the body with intense pruritus, headache, malaise, anorexia, cough, coryza, tiredness and loss of appetite.
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.
CT scan
In Varicella pneumonia the CT shows well-defined and ill-defined nodules diffusely throughout both lungs nodules with a surrounding halo of ground-glass opacity, patchy ground-glass opacity, and coalescence of nodules.
MRI
Ultrasound
Other Imaging Findings
Other Diagnostic Studies
Treatment
Medical Therapy
Surgery
Primary Prevention
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.