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Chickenpox (Varicella): A Highly Contagious Viral Childhood Illness

Chickenpox, also known as varicella, is a sudden, highly contagious viral infection caused by the varicella-zoster virus (VZV), which belongs to the herpesvirus family. It most often affects children and is usually a mild illness that clears up on its own in healthy people. However, chickenpox can cause serious problems in certain vulnerable groups, including babies, people with weakened immune systems, pregnant women, and adults who haven’t had it before.

The illness starts with general symptoms like tiredness, feeling unwell, a mild fever, and loss of appetite. These are followed by the typical rash — a very itchy skin eruption made up of red spots (macules), raised bumps (papules), small blisters (vesicles), pus-filled spots (pustules), and scabs. These different types of spots often appear together at various stages. The rash usually begins on the trunk and quickly spreads to the face, scalp, and limbs. In more severe cases, spots can also appear on the moist areas inside the mouth and around the genitals.

Chickenpox is extremely contagious. It spreads through tiny droplets in the air from coughs or sneezes, or by touching fluid from the blisters. The virus can also be picked up from contaminated surfaces, especially in close settings like homes, schools, and nurseries. People are contagious from about 1 to 2 days before the rash shows up until all the blisters have dried and formed scabs, usually around 7 to 10 days after the rash begins.

Who’s Most at Risk?

Chickenpox mainly affects children aged between 5 and 9 years. But with more children attending early years settings, cases are increasingly seen in younger, preschool-aged children. The infection spreads easily — up to 90% of those who haven’t had chickenpox before will catch it if exposed.

The illness tends to be more common in the winter and spring months, especially in temperate climates. Once you’ve had chickenpox, you usually develop immunity for life, although the virus stays dormant in the body. Sometimes, it can reactivate later in life as shingles (herpes zoster), which causes painful nerve inflammation and a rash, mostly in people over 60 or those with weakened immune systems.

How the Virus Works

After you breathe in the virus or it comes into contact with the lining of your nose or throat, the varicella-zoster virus infects the cells in the upper respiratory tract. It then spreads to nearby lymph nodes and enters the bloodstream (this is called primary viremia). The virus multiplies further in the body’s immune system tissues. A second wave of virus in the blood (secondary viremia) spreads it widely to the skin and mucous membranes, causing the typical rash. The virus also hides in the dorsal root ganglia — clusters of nerve cells — where it can remain inactive for years before possibly reactivating as shingles.

This ability to stay dormant for life is typical of herpesviruses and highlights why early exposure, vaccination, and careful monitoring of people with weakened immunity are so important.

Signs and Symptoms: What Chickenpox Looks Like

Symptoms usually appear 10 to 21 days after catching the virus. The illness often starts with a mild phase marked by tiredness, low fever, headache, feeling unwell, and loss of appetite. In children, this early stage may be very mild or not noticed at all; in adults, these symptoms tend to be more obvious.

Within a day, the classic skin rash appears. It usually begins on the chest and back and then spreads quickly to the face, scalp, arms, legs, and sometimes to the inside of the mouth, eyes, and genital area.

The rash goes through several stages:

Macules: Small, flat red spots that mark the first signs of the rash.
Papules: Raised red bumps that develop within hours.
Vesicles: Tiny blisters filled with clear or yellowish fluid, often described as looking like “dew drops on a rose petal.”
Pustules: Some blisters become cloudy or filled with pus.
Crusts: The spots eventually break open, dry out, and form scabs that fall off after 1 to 2 weeks, usually without leaving scars.

The itching can be intense and may lead to scratching, which raises the chance of a secondary bacterial infection and scarring. The number of spots varies — some people have only a few, while others may develop hundreds.

How Chickenpox Is Diagnosed

Most of the time, doctors diagnose chickenpox by looking at the typical rash at different stages, along with symptoms like fever and feeling unwell. But in unusual cases or for people with weakened immune systems, extra tests might be needed.

These include:

Polymerase Chain Reaction (PCR): The most accurate test to detect varicella-zoster virus DNA from blister fluid, blood, or throat swabs.
Direct Fluorescent Antibody (DFA): A test that can confirm the virus from skin scrapings.
Blood tests: Checking for specific antibodies (IgM and IgG) to see if the infection is recent or happened in the past.

If chickenpox is suspected, especially in babies under 1 year, pregnant women, or those with weakened immunity, it’s important to see a doctor or infectious disease specialist quickly for proper care and monitoring.

How Chickenpox Is Treated

In healthy children without other health problems, chickenpox usually clears up on its own and only needs symptom relief. The aim is to ease discomfort and prevent complications.

Supportive care includes:

Fever relief: Paracetamol is recommended to reduce fever. Avoid aspirin because it can cause a rare but serious condition called Reye’s syndrome.
Antihistamines: Medicines taken by mouth or applied to the skin may help reduce itching.
Calamine lotion or cooling gels: These soothe the skin and ease irritation.
Good hydration and gentle diet: Soft, non-acidic foods and plenty of fluids are important, especially if there are sores in the mouth.
Hygiene: Regular handwashing, keeping nails short, and using antiseptic skin care help prevent infections.
Loose, breathable clothing: This helps avoid skin irritation and overheating.

Antiviral treatment:

For those at higher risk — such as pregnant women, people with weakened immune systems, and newborns — antiviral drugs like acyclovir, valacyclovir, or famciclovir may be prescribed. Treatment works best if started within 24 to 48 hours of symptoms appearing.

Varicella-zoster immune globulin (VZIG) can also be given after exposure to reduce the severity of the illness in vulnerable individuals.

When Chickenpox Can Become Serious

Although usually mild, chickenpox can sometimes cause serious complications that require hospital care and intensive treatment. Common complications include:

Secondary bacterial skin infections: Often caused by Staphylococcus aureus or Streptococcus pyogenes, these may need antibiotics.
Pneumonia: More likely in adults, smokers, and those with weakened immune systems.
Sepsis: A rare but life-threatening infection that needs urgent treatment.
Encephalitis or cerebellar ataxia: Inflammation of the brain or cerebellum, which can cause confusion, seizures, or movement problems.
Congenital varicella syndrome: If a pregnant woman catches chickenpox in the first 20 weeks, the baby may develop birth defects.

People at high risk — especially pregnant women, newborns, those with HIV, cancer patients, and anyone on immune-suppressing treatments — need close monitoring and early antiviral treatment to lower the risk of serious illness or death.

Preventing Chickenpox: How to Stop It Spreading

Chickenpox is contagious from about 1 to 2 days before the rash appears until all the spots have crusted over. This makes stopping the spread tricky, especially in schools and nurseries.

To help reduce transmission:

Anyone with chickenpox should stay at home and avoid contact with others until all the spots have crusted, usually about 5 to 7 days after the rash starts.
Good hand hygiene and cleaning of surfaces are important.
Children with chickenpox shouldn’t go to school, and adults should avoid workplaces where they might come into contact with vulnerable people.

Vaccination

The best way to prevent chickenpox is through vaccination. The varicella vaccine contains a weakened live virus and is given in one or two doses depending on age and local immunisation schedules. One dose offers around 99% protection against severe chickenpox and about 80% protection against all cases.

Vaccinating within 3 to 5 days after exposure can still prevent the illness or make it much milder. Vaccination is especially recommended for:

Children aged 12 months and older;
Adults who haven’t been vaccinated or had chickenpox before;
Healthcare workers and carers of people with weakened immune systems;
Women of childbearing age before pregnancy.

By combining vaccination, good hygiene, and timely medical care, we can greatly reduce the impact of chickenpox and its complications, particularly in those most at risk.