infectious diseases
Chickenpox
Introduction
Chickenpox is an acute, systemic, usually childhood infection caused by the varicella-zoster virus (human herpesvirus type 3). It usually begins with mild constitutional symptoms (eg, fever, malaise) followed shortly by skin lesions appearing in crops and characterized by macules, papules, vesicles, and crusting. Patients at risk of severe neurologic or other systemic complications (eg, pneumonia) include adults, neonates, and patients who are immunocompromised or have certain underlying medical conditions. Diagnosis is clinical. Those at risk of severe complications receive postexposure prophylaxis with varicella immune globulin and, if disease develops, are treated with antiviral medications (eg,valacyclovir,famciclovir,acyclovir). Vaccination provides effective prevention in patients who are immunocompetent. Chickenpox is caused by the varicella-zoster virus (human herpesvirus type 3); chickenpox is the acute invasive phase of the infection, and Herpes Zoster (shingles) represents reactivation of the latent phase. Chickenpox, which is extremely contagious, is spread by Mucosal (usually nasopharyngeal) inoculation via infected airborne droplets or aerosolized particles Direct contact with the virus (eg, via skin lesions) Chickenpox is most communicable during the prodrome and early stages of the eruption. It is communicable from 48 hours before the first skin lesions appear until the final lesions have crusted. Indirect transmission (by carriers who are immune) does not occur. Prior to the advent of the Varicella Vaccine , chickenpox epidemics occurred in winter and early spring in 3- to 4-year cycles. (See Overview of Herpesvirus Infections .) 