Chickenpox (Varicella)

Overview

Chickenpox, also known as varicella, is a highly contagious viral infection caused by the varicella-zoster virus (VZV). This common childhood disease is characterized by an itchy, blister-like rash that appears on the skin and spreads throughout the body. While chickenpox is generally mild in children, it can be more severe in adults, pregnant women, and people with weakened immune systems.

Before the introduction of the chickenpox vaccine in 1995, nearly all children in the United States contracted chickenpox by adulthood. Today, widespread vaccination has dramatically reduced the incidence of this disease. The infection typically provides lifelong immunity, though the virus remains dormant in nerve tissues and can reactivate later in life as shingles (herpes zoster).

Chickenpox spreads easily through respiratory droplets when an infected person coughs or sneezes, and through direct contact with the fluid from chickenpox blisters. The disease is contagious from about 1-2 days before the rash appears until all blisters have crusted over, typically 5-7 days after rash onset.

Symptoms

Chickenpox symptoms typically develop 10-21 days after exposure to the virus. The illness usually begins with mild flu-like symptoms, followed by the characteristic rash. The progression of symptoms follows a predictable pattern that helps healthcare providers diagnose the condition.

Common Symptoms

Less Common Symptoms

The chickenpox rash typically appears first on the chest, back, and face, then spreads to the entire body, including inside the mouth, eyelids, and genital area. The rash progresses through three stages: raised red bumps (papules), fluid-filled blisters (vesicles), and crusts and scabs. New spots continue to appear for several days, so all three stages may be present simultaneously.

Causes

Chickenpox is caused by the varicella-zoster virus (VZV), a member of the herpesvirus family. This highly contagious virus spreads through multiple routes and can survive briefly on surfaces and in the air.

Primary Transmission Methods

• Airborne transmission: The virus spreads through respiratory droplets when an infected person coughs, sneezes, or talks. These droplets can remain suspended in the air and be inhaled by others.
• Direct contact: Touching the fluid from chickenpox blisters can transmit the virus. This includes contact with clothing, bedding, or other items contaminated with blister fluid.
• Mother to baby: Pregnant women who develop chickenpox can transmit the virus to their unborn baby, potentially causing congenital varicella syndrome.
• From shingles: A person with active shingles can transmit the varicella-zoster virus to someone who has never had chickenpox, causing them to develop chickenpox (not shingles).

Once infected, the virus multiplies in the respiratory tract and spreads to the lymph nodes. From there, it enters the bloodstream and disseminates throughout the body, causing the characteristic rash and systemic symptoms. After recovery, the virus remains dormant in nerve cells and can reactivate years later as shingles.

The incubation period for chickenpox is typically 14-16 days but can range from 10-21 days. During this time, the infected person shows no symptoms but becomes contagious 1-2 days before the rash appears.

Risk Factors

While anyone who hasn't had chickenpox or been vaccinated can contract the disease, certain groups face higher risks of infection or complications:

Groups at Higher Risk

• Unvaccinated individuals: Those who haven't received the chickenpox vaccine are at highest risk
• Children under 12: Most susceptible age group, though vaccination has reduced incidence
• Pregnant women: Risk of complications for both mother and baby
• Immunocompromised individuals: Including those with HIV/AIDS, cancer patients on chemotherapy, and organ transplant recipients
• Adults: Tend to have more severe symptoms than children
• Healthcare workers: Increased exposure to infected patients
• Teachers and childcare providers: Regular contact with children increases exposure risk

Environmental Risk Factors

• Living in close quarters (dormitories, military barracks)
• Attending school or daycare during outbreaks
• International travel to areas with low vaccination rates
• Seasonal patterns (late winter and early spring peaks)

Diagnosis

Chickenpox is typically diagnosed based on the characteristic appearance and distribution of the rash. Healthcare providers can usually identify chickenpox through visual examination, though laboratory tests may be necessary in atypical cases or for high-risk patients.

Clinical Diagnosis

The diagnosis is usually made by observing:

• The distinctive rash pattern starting on the trunk and spreading outward
• Presence of lesions in multiple stages (papules, vesicles, and crusts)
• Associated symptoms like fever and itching
• Recent exposure history (contact with infected individuals)
• Vaccination status

Laboratory Tests

When clinical diagnosis is uncertain, several tests can confirm chickenpox:

• Direct fluorescent antibody (DFA) test: Detects varicella-zoster virus antigens in skin lesion specimens
• Polymerase chain reaction (PCR): Most sensitive test for detecting VZV DNA in vesicle fluid, blood, or other specimens
• Viral culture: Can isolate the virus from vesicle fluid, though less sensitive than PCR
• Blood tests: Detect VZV-specific antibodies (IgM for acute infection, IgG for past infection or immunity)
• Tzanck smear: Microscopic examination of cells from vesicle base, though cannot distinguish between VZV and herpes simplex virus

Differential Diagnosis

Conditions that may be confused with chickenpox include:

• Herpes simplex
• Impetigo
• Insect bites
• Hand, foot, and mouth disease
• Drug reactions
• Scabies

Treatment Options

Treatment for chickenpox focuses primarily on relieving symptoms and preventing complications. Most healthy children recover without specific medical treatment, while high-risk individuals may require antiviral therapy.

Symptomatic Treatment

• Fever management: Acetaminophen for fever reduction (avoid aspirin due to Reye's syndrome risk)
• Itch relief: Calamine lotion, cool baths with oatmeal or baking soda, antihistamines like diphenhydramine
• Prevent scratching: Keep fingernails short, use mittens on young children at night
• Skin care: Keep skin clean and dry, avoid harsh soaps
• Hydration: Encourage fluid intake to prevent dehydration
• Rest: Adequate sleep and reduced activity during acute phase

Antiviral Medications

Antiviral therapy may be recommended for:

• Adolescents and adults
• People with chronic skin or lung conditions
• Those on long-term salicylate therapy
• Immunocompromised patients
• Pregnant women

Common antiviral medications include:

• Acyclovir: Most commonly prescribed, most effective when started within 24 hours of rash onset
• Valacyclovir: Prodrug of acyclovir with better oral bioavailability
• Famciclovir: Alternative antiviral option

Prevention of Secondary Infections

• Keep blisters clean and avoid scratching
• Watch for signs of bacterial infection (increased redness, warmth, or pus)
• Antibiotics only if secondary bacterial infection develops

Isolation Measures

• Stay home from school or work until all blisters have crusted
• Avoid contact with high-risk individuals
• Cover mouth when coughing or sneezing
• Frequent handwashing

Prevention

The most effective way to prevent chickenpox is through vaccination. The varicella vaccine has dramatically reduced the incidence and severity of chickenpox since its introduction.

Vaccination Schedule

• Children: Two doses - first at 12-15 months, second at 4-6 years
• Adolescents and adults: Two doses given 4-8 weeks apart if no evidence of immunity
• Healthcare workers: Two doses recommended for those without evidence of immunity
• Postexposure prophylaxis: Vaccine within 3-5 days of exposure may prevent or reduce severity

Other Prevention Strategies

• Avoid exposure: Stay away from infected individuals during contagious period
• Good hygiene: Regular handwashing, especially after contact with infected persons
• Immune globulin: For high-risk individuals exposed to chickenpox who cannot be vaccinated
• Environmental measures: Disinfect contaminated surfaces and wash bedding in hot water

The vaccine is about 90% effective at preventing chickenpox. Even if vaccinated individuals do contract chickenpox (breakthrough varicella), the illness is typically much milder with fewer lesions and complications.

When to See a Doctor

While chickenpox is usually mild in healthy children, certain situations require medical attention:

Seek Immediate Medical Care If:

• Difficulty breathing or persistent cough
• High fever (over 102°F) lasting more than 4 days
• Severe headache, stiff neck, or confusion
• Difficulty walking or severe dizziness
• Repeated vomiting
• Signs of dehydration
• Rash becomes very red, warm, or tender (signs of bacterial infection)
• Bleeding from the rash

Contact Your Healthcare Provider If:

• Anyone in your household is immunocompromised
• You're pregnant and exposed to chickenpox
• The patient is an adolescent or adult
• The patient has a chronic medical condition
• You're unsure about the diagnosis
• Symptoms worsen despite home treatment

Related Conditions

References

1. Centers for Disease Control and Prevention. Chickenpox (Varicella). Updated 2021.
2. American Academy of Pediatrics. Red Book: 2021-2024 Report of the Committee on Infectious Diseases.
3. Gershon AA, et al. Varicella zoster virus infection. Nature Reviews Disease Primers. 2015.
4. World Health Organization. Varicella and herpes zoster vaccines: WHO position paper. 2014.
5. Marin M, et al. Prevention of varicella: recommendations of the Advisory Committee on Immunization Practices. MMWR. 2007.