Smallpox: Everything You Need to Know

Medically Reviewed By Karen Gill, M.D.

Smallpox was a contagious disease caused by the Variola virus. Symptoms of the potentially fatal illness included fever, a progressive rash, and sores. Following the development of a vaccine, smallpox was declared eradicated in 1980. Smallpox was a serious disease that resulted in the deaths of around every 3 in 10 people Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source affected. Individuals who survived the virus were often left with permanent scars on their face and body. Some were also left blind.

No naturally occurring cases of smallpox have occurred since 1977. The last known case of smallpox in the United States was in 1949. In 1980, the World Health Organization (WHO) Trusted Source World Health Organization Highly respected international organization Go to source declared that smallpox had been eradicated.

Read on to learn more about the history of smallpox, what caused the disease, and how we finally eradicated it.

What is smallpox?

A boy with spots on his body is playing with a dog.
Liliya Rodnikova/Stocksy United

Smallpox was a contagious disease caused by the Variola virus. Initial symptoms Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source included fever, headaches, and back pain. As the illness progressed, symptoms would include a rash and small, raised bumps on the skin.

The disease could spread through person-to-person contact or through direct contact with contaminated materials, such as clothing or bed linen.

Visit our infections and contagious diseases hub here.

Different types of smallpox

The two different types of smallpox were Variola major and Variola minor. Variola minor was less common and much less severe than Variola major, with around 1% or fewer Trusted Source Food and Drug Administration (FDA) Governmental authority Go to source cases resulting in death.

Variola major was the more severe strain of smallpox, with around 30% of cases resulting in death. This type of smallpox was divided into four subtypes Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source . These were as follows:

  • Ordinary smallpox: Ordinary smallpox caused the most cases of smallpox, accounting for around 85% of all cases.
  • Modified smallpox: Individuals who had been vaccinated against smallpox experienced milder symptoms of smallpox. This disease was known as modified smallpox.
  • Flat smallpox: Flat, or malignant, smallpox was a rare version of the disease that occurred more frequently in children. Skin lesions developed more slowly and merged. With this strain, legions did not progress to the pustular stage.
  • Hemorrhagic smallpox: Hemorrhagic smallpox could affect anybody of any age, but it was more common among adults — particularly pregnant people. Symptoms appeared more quickly following infection, with death often occurring 5 or 6 days after the rash first appeared.

Vs. monkeypox

Symptoms of monkeypox are similar to those of smallpox, but they are typically milder Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source . Symptoms include fever, headaches, muscle aches, and exhaustion. These then progress to a rash, lesions, and scabs.

A person can have monkeypox without displaying any symptoms for around 7–14 days. This is similar to the average 10–14 days it took for an individual with smallpox to begin to show symptoms of the disease.

The main difference between the two diseases is that monkeypox causes the lymph nodes to swell. This did not occur in cases of smallpox.

Monkeypox can be fatal. In fact, 1 in 10 people in Africa who contract the infection may die as a result.

Does smallpox still exist?

The last known case Trusted Source World Health Organization Highly respected international organization Go to source of naturally occurring smallpox was in Somalia in 1977. Ethiopia and Kenya were also among the last countries in the world with known cases of smallpox.

Today, the only known samples of smallpox are in Atlanta and Russia, where laboratories securely keep stockpiles of the disease for research.

There is no evidence to suggest that smallpox exists outside of these laboratories.

How was smallpox eradicated?

Smallpox was eradicated partly due to the development of the smallpox vaccine and partly because of the WHO’s ability to trace and monitor people who had it.

When Ali Maow Maalin contracted smallpox in Somalia in 1977, the WHO helped him quarantine. They also administered the vaccine to approximately 50,000 people in the houses nearby over the course of 14 days.

Ali Maow Maalin recovered from the disease. This was the last known case of smallpox worldwide.

What are the symptoms of smallpox?

Smallpox typically presented different symptoms at different stages of the disease. The stages and symptoms developed as follows Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source :

  • Incubation period: This is the time between when a person contracts an infection and when they first begin to show symptoms. With smallpox, this could last 7–19 days, though it typically lasted 10–14 days. The disease was not contagious during this time.
  • Initial symptoms: Initial smallpox symptoms began to show for around 2–4 days, with symptoms including high fever, headaches, body aches, and occasional vomiting. The disease could sometimes be contagious during this stage.
  • Early rash: The early rash developed over the course of around 4 days, during which time the disease was the most contagious. The rash would typically start as small, red spots on the tongue and in the mouth, and these would change into sores that would spread large amounts of virus. Once the sores opened, a rash would appear on the face and spread to the arms, legs, hands, and feet within around 24 hours. By the end of this stage, the skin sores were filled with a thick, opaque fluid.
  • Pustular rash and scabs: This stage lasted around 10 days, and the disease was still contagious during this time. The sores became sharply raised and firm to the touch. After around 5 days, they formed a crust and scabbed over.
  • Scabs falling off: Over the course of around 6 days, the scabs fell off and left marks on the skin. By around 3 weeks after the rash first appeared, most of the scabs had fallen off. The disease remained contagious at this time.
  • Final stage: All of the scabs had typically fallen off around 4 weeks after the rash first appeared. Once all of the scabs had fallen off, the disease was no longer contagious.

How many people died from smallpox?

Smallpox was a serious disease, with around 3 in 10 people Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source dying as a result. It is estimated that smallpox was responsible for around 300 million deaths since 1900.

When did smallpox begin?

Although the origin of smallpox is not known, it is believed that it may have existed as far back as around 3,000 years ago Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source . The first record of smallpox appeared in China in the 4th century CE.

It is suggested that smallpox had reached parts of Europe by the 7th century. Central and South America were affected by the 16th century, and North America saw cases of smallpox by the 17th century.

What caused smallpox to spread?

The smallpox virus spread from one person to another following close contact. This included direct skin-to-skin contact and breathing in particles when near the affected individual.

It was also possible to contract smallpox as a result of handling contaminated materials, such as clothing or bed linen. However, contaminated materials would only remain contagious for around 2 days.

What is the smallpox vaccine?

English doctor Edward Jenner began to develop Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source the vaccine against smallpox in 1796. He noticed that people who had had cowpox were protected against smallpox.

Following a period of experimentation, the cowpox virus in the smallpox vaccine was replaced with the Vaccinia virus in the 1800s.

In 1959, with the help of the vaccine, the WHO started a plan to eradicate smallpox.

Who can get the smallpox vaccine?

The smallpox vaccine is no longer routinely distributed. It was last offered to the American public in 1972, as routine vaccinations for the virus were no longer needed.

The only people offered the smallpox vaccine today are laboratory workers who are at risk of exposure to the virus and other viruses that are similar to it. The vaccine may also be given to some people who serve in the military.

Are there any complications of the smallpox vaccine?

The smallpox vaccine is generally considered safe. However, like most vaccines, it may cause some side effects. Common side effects can include Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source :

More serious side effects of the smallpox vaccine include:

  • heart problems
  • accidental infection of the eye
  • severe skin diseases
  • swelling of the brain or spinal cord
  • severe allergic reactions
  • spreading of the virus to other parts of the body

People who are at greater risk of side effects from the vaccine include:

The site of the vaccine will develop a dime-sized lesion that will form a scab and leave a scar. The fluid and crusts of the lesion are contagious until the scab forms, so it is important that anybody who receives the vaccine properly covers the vaccination site to prevent the virus from spreading.

How do doctors diagnose smallpox?

If a person presents symptoms of smallpox in the same order that they have been known to develop, a doctor would take samples to carry out laboratory testing Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source to either confirm or rule out smallpox.

As the likelihood of a smallpox diagnosis is low, only individuals who meet all three criteria will be tested. These criteria are as follows:

  • fever higher than 101°F (38.3°C) around 1–4 days before the rash appears, alongside one of the following:
  • classic smallpox lesions
  • all lesions in the same stage of development on any part of the body

If all of the criteria are met, a doctor would class it as a probable case of smallpox pending laboratory results.

How do doctors treat smallpox?

There is currently no proven treatment for smallpox. If someone receives a diagnosis of smallpox, they would be offered supportive therapy and given antibiotics for any bacterial infections.

An individual with smallpox would be monitored in isolation to prevent them from transmitting the infection to another person. This would help prevent a smallpox outbreak.

Will there ever be a smallpox treatment?

In recent years, antiviral medications have been tested and approved Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source for the treatment of smallpox. These include tecovirimat (Tpoxx) and brincidofovir (Tembexa). Cidofovir has also been shown to stop the growth of the virus that causes smallpox.

However, these antiviral drugs have not been tested in people who have contracted smallpox. Therefore, it is not possible to know if they would provide an effective treatment for this infection.

Will smallpox ever return?

Although it is not possible to know if smallpox will ever return, there are only two known stockpiles of the virus currently in existence. These are kept in laboratories in Atlanta and Russia. If one case of smallpox were to be confirmed, this would be an international emergency.

Plans are currently in place should an outbreak ever occur. These include:

  • activating response plans developed by some state health departments
  • administering drugs recently approved Trusted Source American Journal of Clinical Nutrition Peer reviewed journal Go to source by the Food and Drug Administration (FDA) for the treatment of smallpox
  • using the WHO’s emergency vaccine stockpile

The WHO also provides advice Trusted Source World Health Organization Highly respected international organization Go to source on approaches to managing an outbreak of smallpox.

Can bioterrorism cause a smallpox outbreak?

There are some concerns that the smallpox virus may be used for bioterrorism, wherein terrorists deliberately release the virus from where the few remaining samples are kept in laboratories.

This is considered to be a very low risk.

Summary

Smallpox was a serious contagious disease that killed around 3 in 10 people who developed it. Records suggest that the virus existed for at least 3,000 years and caused around 300 million deaths since 1900.

Symptoms of smallpox included fever and body aches, followed by a rash and sores that would turn into scabs. Once a person contracted the infection, it could take up to 19 days for them to develop a contagious disease. The infection mostly spread through person-to-person contact, though individuals could also contract it by handling contaminated clothing or bed linen.

Following the development of the smallpox vaccine, the WHO launched a plan to eradicate smallpox. This plan proved successful, with the last known case of smallpox in the U.S. occurring in 1949. The last naturally occurring case of smallpox was in Somalia in 1977.

In 1980, the WHO declared that smallpox had been eradicated.

Was this helpful?
3

Medical Reviewer: Karen Gill, M.D.
Last Review Date: 2022 Mar 29
View All Infectious Diseases Articles
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.