Chickenpox (varicella)

Overview

Chickenpox, also called varicella, is a highly contagious infection caused by varicella-zoster virus. After primary infection the virus remains latent in sensory nerve ganglia and can later reactivate as herpes zoster (shingles). ^{[1] [2]}

VZV spreads mainly through respiratory exposure and direct contact with fluid from skin lesions. After replication in the respiratory tract and lymphatic tissues, viremia disseminates virus to the skin, producing crops of macules, papules, clear vesicles and crusted lesions that can coexist at the same time. ^{[1] [2]}

In otherwise healthy children, varicella is often self-limited. Disease tends to be more severe in adolescents and adults, during pregnancy, in newborns around the time of maternal infection, and in people with significant immune compromise. Breakthrough varicella after vaccination can be milder and may have fewer vesicles, which can make clinical recognition less obvious. ^{[1] [2] [3]}

Symptoms and warning signs

The classic rash begins as small red spots that become fluid-filled vesicles and then crust. New lesions continue to appear for several days, so macules, papules, vesicles and scabs are often visible together. Rash commonly begins on the chest, back or face before spreading and can involve the scalp and mucous membranes. Fever and malaise may start before the rash, especially in adults. ^{[1] [2]}

Urgent assessment is important for breathing difficulty, severe neurologic symptoms, dehydration, rapidly spreading redness or pus around lesions, or severe disease in a pregnant, newborn or immunocompromised patient. Adults with cough, shortness of breath or chest pain need prompt evaluation because varicella pneumonia can be serious. ^{[1] [2]}

Diagnosis

Chickenpox is often diagnosed clinically when the characteristic generalized vesicular rash appears in crops. Vaccination has made atypical or mild breakthrough presentations more common, so laboratory confirmation becomes more useful when the appearance is not classic, during outbreaks, in high-risk patients or when the diagnosis would change infection-control or treatment decisions. ^{[1] [2]}

PCR testing of material from vesicles, scabs or other skin lesions is the preferred laboratory method for confirming varicella. Serology has more limited roles in acute diagnosis. When complications are suspected, testing is directed to the affected system—for example chest imaging for pneumonia or neurologic evaluation for encephalitis or cerebellar complications. ^{[1] [2] [3]}

The differential includes disseminated herpes zoster, herpes simplex, hand-foot-and-mouth disease, impetigo, insect bites, scabies and other vesicular or pustular eruptions. Distribution, lesion evolution, exposure history, vaccination status and PCR testing help distinguish these conditions. ^{[2] [3]}

Causes, risk factors and clinical context

Recognized risk factors and clinical contexts include No immunity or vaccination, Household or close exposure, Adolescence or adulthood, Pregnancy, Immune compromise, and Newborn exposure around delivery. Risk factors change pre-test probability but do not diagnose the condition by themselves; their importance depends on the individual patient and the rest of the clinical picture. ^{[1] [2]}

New skin lesions usually appear over several days and then crust. A person is generally considered contagious from about 1–2 days before the rash until all lesions have crusted; in vaccinated breakthrough disease without vesicles, public-health guidance may use absence of new lesions for 24 hours. Recovery is usually complete, but VZV remains latent and can reactivate years later as shingles. ^{[1] [2] [3]}

Complications and why the diagnosis matters

Potential complications include Bacterial infection of skin lesions, Varicella pneumonia, Encephalitis or cerebellar ataxia, Dehydration, Sepsis in severe infection, and Pregnancy and neonatal complications. The practical reason to identify Chickenpox (varicella) accurately is to prevent avoidable morbidity, recognize people who need specialist or emergency care, and avoid therapies that could be ineffective or harmful for a different diagnosis. ^{[1] [2]}

Most healthy children recover without lasting problems. The risk of hospitalization and severe complications is higher in adults and immunocompromised patients. Pneumonia, encephalitis, invasive bacterial infection and neonatal varicella can be life-threatening, which is why prevention and early risk stratification matter. ^{[1] [2] [3]}

Treatment and management

Uncomplicated chickenpox is managed with fluids, rest, fever and itch control, and measures to prevent scratching and secondary skin infection. Aspirin should not be given to children or adolescents with varicella because of the association with Reye syndrome. Antiviral therapy such as acyclovir is used for selected patients at higher risk or with severe disease; timing and route depend on clinical circumstances. ^{[1] [2]}

Keep nails short, use gentle skin care, maintain hydration and use age-appropriate symptom relief. Infection-control advice is important because susceptible pregnant people and immunocompromised contacts may face a high risk of severe disease. School, work and household precautions should follow local public-health guidance. ^{[1] [2] [3]}

Antiviral decisions should account for time from rash onset, age, pregnancy, renal function, immune status and disease severity. Severe varicella or disease in immunocompromised patients may require hospital care and intravenous antiviral treatment. Antibiotics do not treat VZV but may be needed for proven secondary bacterial infection. ^{[1] [2]}

Follow-up, recovery and prevention

Routine follow-up is not always needed for a healthy child who is improving. Reassessment is appropriate if fever returns after improvement, lesions become very red or painful, breathing symptoms appear, neurologic symptoms develop, or oral intake becomes inadequate. High-risk patients should have a lower threshold for clinician follow-up. ^{[1] [2]}

Varicella vaccination is the principal preventive strategy. Post-exposure management depends on susceptibility and risk: eligible people may receive vaccine after exposure, while certain high-risk susceptible contacts may need varicella-zoster immune globulin or antiviral strategies according to current guidance. ^{[1] [2] [3]}

Special situations and care pathway

Pregnancy, the neonatal period and immune compromise require individualized management. Maternal varicella can cause severe maternal pneumonia and, depending on timing, fetal or neonatal complications. Live varicella vaccine is not used during pregnancy or in some forms of severe immune suppression, so prevention planning should occur before exposure when possible. ^{[1] [2] [3]}

For a typical mild case, primary care or telehealth may confirm the diagnosis and give symptom and isolation advice. High-risk hosts, uncertain diagnosis, severe rash, pneumonia, neurologic symptoms or systemic deterioration require in-person assessment, and some patients need infectious-disease, obstetric, neonatal or hospital care. ^{[1] [2]}

When to seek urgent medical care

Seek urgent care for breathing difficulty, chest pain, severe drowsiness or confusion, repeated vomiting with dehydration, difficulty walking, rapidly worsening skin infection, or severe chickenpox in pregnancy, a newborn or an immunocompromised patient. ^{[1] [2]}

Sources

1. CDC — Clinical Overview of Chickenpox (Varicella)
2. CDC — Clinical Features of Chickenpox (Varicella)
3. CDC — About Chickenpox
4. MedlinePlus — Chickenpox

This article is based on trusted medical sources and is awaiting clinician review. It is not a substitute for personalized medical advice.