varicella

Varicella, commonly known as chickenpox, is caused by varicella-zoster virus (VZV), a herpesvirus. It is highly contagious, spreading through respiratory droplets and direct contact with vesicle fluid. The incubation period is typically 10 to 21 days, with most cases developing within two to three weeks. People are contagious from about one to two days before the rash appears until all lesions have crusted.

Clinically, varicella presents with an itchy, widespread vesicular rash that usually begins on the face and trunk and then spreads to the limbs. Lesions appear in successive crops, evolving from red macules to fluid-filled vesicles and then crust over several days. Fever, malaise, and poor appetite are common. In healthy children the illness is usually mild, while adults are at higher risk for pneumonia and other complications. Bacterial skin infections can occur secondary to scratching.

Diagnosis is usually clinical, but vesicular fluid can be tested by PCR or direct fluorescent antibody assays to confirm VZV. Prevention relies on vaccination: live attenuated varicella vaccines are given in two doses in many countries and substantially reduce incidence and severity. Post-exposure prophylaxis with vaccination or varicella-zoster immune globulin is available for certain high-risk individuals within specified time frames.

Treatment is largely supportive, including fluids, rest, and relief from fever and itching. Antiviral therapy with acyclovir (or valacyclovir) is recommended for adults, pregnant women near term, individuals with severe disease, and those who are immunocompromised. Aspirin should be avoided due to the risk of Reye syndrome. Varicella can reactivate later in life as herpes zoster (shingles).