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InfectiousICD-10: B01.9Prior to vaccination, about 4 million cases occurred annually in the U.S.

Chickenpox

Also known as: Varicella

Chickenpox is a highly contagious viral infection caused by the varicella-zoster virus (VZV) that produces an itchy, blister-like rash covering the body. It primarily affects children but can be more severe in adolescents, adults, and immunocompromised individuals. Since the introduction of the varicella vaccine, chickenpox incidence has declined by more than 90% in vaccinated populations.

Symptoms

Itchy rash progressing from red spots to fluid-filled blisters to crusted scabs
Rash appearing in successive waves over 5-7 days
Fever (usually 101-102°F / 38.3-38.9°C)
Fatigue and malaise
Loss of appetite
Headache
Body aches

Causes

  • Infection with the varicella-zoster virus (VZV)
  • Spread through respiratory droplets or direct contact with blister fluid
  • Highly contagious from 1-2 days before rash onset until all blisters have crusted

Risk Factors

  • Not being vaccinated against varicella
  • Close contact with an infected person
  • Being under 12 years of age (most common age group)
  • Weakened immune system
  • Pregnancy (risk of complications for mother and baby)

Diagnosis

  • Clinical diagnosis based on characteristic rash appearance
  • PCR testing of blister fluid for varicella-zoster virus
  • Blood test for varicella IgM antibodies

Treatment

  • Calamine lotion and oatmeal baths to relieve itching
  • Antihistamines (diphenhydramine) for itch relief
  • Acetaminophen for fever (avoid aspirin in children)
  • Antiviral medication (acyclovir) for high-risk patients
  • Keep nails short and avoid scratching to prevent secondary infection

Prevention

  • Varicella vaccine (2 doses recommended for children)
  • Post-exposure prophylaxis with vaccine within 3-5 days of exposure
  • Varicella-zoster immune globulin (VZIG) for high-risk exposed individuals
  • Isolate infected individuals until all blisters have crusted over

When to See a Doctor

  • The rash spreads to the eyes or becomes very red, warm, and tender
  • Fever exceeds 102°F (38.9°C) or lasts more than 4 days
  • A household member is immunocompromised or pregnant
  • The patient develops difficulty breathing, confusion, or stiff neck

Frequently Asked Questions

Related Conditions

Common Cold

Infectious

Dengue Fever

Infectious

Dermatitis

Dermatological

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Medical Disclaimer: This content is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.

Content reviewed against peer-reviewed medical literature and clinical guidelines. Read our editorial standards.