Chickenpox is caused by the varicella-zoster virus, also known as human herpes virus 3.
Mode of transmission is by droplet infection from the upper respiratory tract or from the discharge by ruptured lesions on the skin.
The incubation period is about 14-21 days.
The disease is contagious till pustules disappear.
The characteristic rash first appears on the trunk on the 2nd day of illness, and then the face, and finally on the limbs. The lesions are maximum on the trunk and minimum on the periphery of the limbs.
The characteristic lesions appear as macules and progress to papules, vesicles and pustules. The lesions finally dry up to form scabs.
The lesions appear in crops, so that lesions at all stages of development are seen in any area at the same time. Low grade fever is often present.
In immunocompromised patients, the lesions are haemorrhagic and are numerous. Dissemination to other organs is quite frequent.
Reye's syndrome with aspirin use
A Tzanck smear of vesicular fluid demonstrates multinucleated giant cells and epithelial cells with eosinophilic intranuclear inclusion bodies.
Isolation of virus through culture of vesicular fluid.
Direct immunofluorescence test to detect virus is easier than culture.
Polymerase chain reaction to identifying viral gene.
No treatment is required in majority of cases.
Symptomatic treatment includes antihistamines and local calamine lotion.
Acyclovir (15 mg/kg five times a day for 7 days) can be used in adults or immunocompromised patients. Other drugs which can be used include valaciclovir (1000 mg TID) and famciclovir (500 mg TID).
In healthy children, use of antiviral agents may reduce the duration of disease when given within 24 hours of symptoms.
Secondary bacterial infection is treated with local antiseptic or systemic antibiotics like cloxacillin.
A live attenuated vaccine is available for the prevention of chickenpox in immunocompetent children and adults who
are at a high risk of infection. It should not be given to pregnant or immunocompromised patients.
Passive prophylaxis using zoster immune globulin (ZIG) or varicella-zoster immune globulin (VZIG) may be given
to immunocompromised persons with history of significant exposure within last 96 hours.