Smallpox – Symptoms and Causes

What Is Smallpox?

Smallpox is a serious, highly contagious disease caused by the variola virus. The disease is now considered eradicated worldwide, with the last natural case occurring in 1977.

In 1980, the World Health Organization declared smallpox globally eliminated following decades of coordinated vaccination efforts.

Historically, smallpox was one of the most deadly diseases, killing about 30% of those infected and leaving many survivors with permanent physical effects.

Symptoms

Smallpox infection develops after an incubation period of 7–19 days, during which a person shows no symptoms and is not contagious.

The illness typically begins with:

• High fever (101-104°F or 38.3-40°C)
• Severe headache
• Backache
• Muscle pain
• Extreme fatigue
• Vomiting (in some cases)

After these initial symptoms, a characteristic rash appears. The rash progresses through several distinct stages:

1. Small red spots first appear on the tongue and in the mouth.
2. Sores develop in the mouth and throat, which break open and spread large amounts of virus into the mouth and throat.
3. Skin rash emerges, starting on the face and spreading to the arms and legs, then to the hands and feet.
4. Raised bumps form within 1-2 days.
5. Fluid-filled blisters develop by day 4.
6. Pustules (firm, round lesions filled with pus) form by day 7.
7. Scabs begin to form by the second week.
8. Scabs fall off after about 3-4 weeks, leaving pitted scars.

The rash is distinct from other diseases because all spots develop at the same rate, unlike chickenpox where spots appear in successive crops.

Smallpox lesions appear more deeply embedded in the skin and are found on the palms and soles, which rarely occurs with chickenpox.

People remain contagious until all scabs have fallen off.

What Causes Smallpox

Smallpox is caused by the variola virus, a member of the orthopoxvirus family. The virus spreads mainly through direct contact with an infected person or contaminated materials such as bedding or clothing.

Modes of transmission include:

• Inhalation of droplets from coughing or sneezing
• Touching infected skin lesions
• Handling contaminated personal items

Smallpox does not spread through animals or insects—only humans can carry and transmit the disease.

There are two types of smallpox virus:

• Variola Major – the more severe form, with a higher fatality rate.
• Variola Minor – a milder form, causing fewer deaths.

The virus is most contagious during the first week of symptoms, particularly when the rash appears.

Risk Factors

Factors that increased the risk of catching smallpox historically included:

• Close contact with infected individuals
• Living in crowded conditions
• Limited access to proper hygiene facilities
• Lack of vaccination

While these no longer apply in modern times due to eradication, they are important for understanding past outbreaks and for preparedness in case of future biological threats.

Complications

Smallpox, if contracted, can lead to several serious health problems. About 30% of people who get smallpox may die from the disease. Survivors often face lasting effects.

The most common complication is permanent scarring. These scars typically appear on the face, arms, and legs where the rash was most severe. Some scars can be deep and cause disfigurement.

Blindness may occur in about 1% of cases. The virus can affect the cornea, causing scarring and vision loss. This happens when pustules form on or near the eyes.

Limb deformities sometimes develop, especially in children. The virus can affect growing bones and joints, leading to growth problems or arthritis.

Other possible complications include:

• Encephalitis (brain inflammation)
• Pneumonia
• Secondary bacterial infections
• Bone infections
• Sepsis (bloodstream infection)

Pregnant women with smallpox face higher risks. The disease often leads to miscarriage or premature birth. Babies born to mothers with active smallpox rarely survive.

Some smallpox survivors develop a problem called “post-smallpox osteomyelitis,” an inflammation of bone that can occur years after recovery from the initial infection.

Preventing Smallpox

People who were vaccinated against smallpox before routine vaccinations ended in the 1970s may still have partial immunity.

Benefits include:

• Reduced risk of severe disease if exposed
• Lower likelihood of death
• Milder symptoms compared to unvaccinated individuals

Vaccination leaves a small round scar on the upper arm. This scar indicates a controlled immune response that trained the body to fight off real infection.

If smallpox ever re-emerged, previously vaccinated people would likely need a booster, while others would require full vaccination.