Following primary infection there is usually lifelong protective immunity from further episodes of chickenpox.
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.
Touching the fluid from a chickenpox blister can also spread the disease. A person with chickenpox is infectious from one to five days before the rash appears.
The crust usually falls off after seven days sometimes leaving a crater-like scar. Although one lesion goes through this complete cycle in about seven days, another hallmark of chickenpox is that new lesions crop up every day for several days. Therefore it may be a week before new lesions stop appearing and existing lesions crust over. Children should not be sent back to school until all lesions have crusted over.
The highly contagious nature of VZV explains the epidemics of chickenpox that spread through schools as one child who is infected quickly spreads the virus to many classmates. High viral titers are found in the characteristic vesicles of chickenpox; thus, viral transmission may also occur through direct contact with these vesicles, although the risk is lower.
It is feared that there would be a greater number of cases of shingles in adults, until the vaccination was given to the entire populationbecause adults who have had chickenpox as a child are less likely to have shingles in later life if they have been exposed occasionally to the chickenpox virus (for example by their children). This is because the exposure acts as a booster vaccine.
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.
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.
Ninety percent of cases of varicella pneumonia occur in the adult population. Rarer complications of disseminated chickenpox also include myocarditis, hepatitis, and glomerulonephritis.
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.
Source: Wikipedia > Chickenpox
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