What Is Smallpox?

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Smallpox is a highly contagious disease caused by the variola virus. It was eradicated by worldwide vaccination in 1980, meaning that it no longer occurs naturally. The last natural outbreak in the United States was in 1949.

Before this, smallpox was one of the most deadly diseases for thousands of years, killing three out of every 10 people who contracted it and leaving many others with permanent scars or blindness. The early symptoms are similar to the flu and a rash develops within a few days, causing deep blisters that scab and fall off.


The origin of smallpox is uncertain, but it's believed to have originated in Egypt or India. Smallpox reached Europe between the fifth and seventh centuries and was present in major European cities by the 18th century. Epidemics occurred in the North American colonies in the 17th and 18th centuries.

At one time, smallpox was a significant disease in every country throughout the world except Australia and a few isolated islands. Millions of people died worldwide, especially in Europe and Mexico, as a result of widespread smallpox epidemics.

The fall of smallpox began with the realization that survivors of the disease were immune for the rest of their lives. This led to the practice of variolation—a process of exposing a healthy person to infected material from a person with smallpox in the hopes of producing smallpox in a milder form that provided immunity from further infection.

The first written account of variolation describes a Buddhist nun practicing it around 1022 to 1063 AD. She would grind up scabs taken from a person infected with smallpox into a powder and then blow it into the nostrils of a non-immune person. By the 1700s, this method of variolation was common practice in China, India, and Turkey. In the late 1700s, European physicians used this and other methods of variolation.

Some people who were variolated still died of smallpox, but this practice drastically decreased the total number of smallpox fatalities.

The next step towards the eradication of smallpox occurred with the observation by an English physician, Edward Jenner, that milkmaids who developed cowpox (a less serious disease) didn't develop smallpox symptoms when they were exposed to variolation. With that discovery, in 1796, Jenner took the fluid from a cowpox pustule on a dairymaid's hand and inoculated a 9-year-old boy.

Six weeks later, he exposed the boy to smallpox and the boy did not develop any symptoms. Jenner coined the term "vaccine" from the word "vaca," which means "cow" in Latin. His work was initially criticized but soon was rapidly accepted and adopted. By 1800, about 100,000 people had been vaccinated in Europe.

The modern vaccine that was licensed by the Food and Drug Administration (FDA) was taken from a weak strain of virus called the "New York City Board of Health" strain. It was produced by Wyeth Laboratories and licensed under the name Dryvax.

The last outbreak of smallpox in the United States occurred in Texas in 1949 with eight cases and one death. Even though most of North America, Western Europe, Australia, and New Zealand were free of smallpox by this time, other countries such as Africa and India continued to suffer from epidemics.

In 1967, the World Health Organization (WHO) started a worldwide campaign to eradicate smallpox. This goal was accomplished in 10 years due in large part to massive vaccination efforts. The last endemic case of smallpox occurred in Somalia in 1977. On May 8, 1980, the World Health Assembly declared the world free of smallpox—a true accomplishment.

The United States stopped vaccinating the general population in 1972 but continued to vaccinate military personnel. It was recommended that vaccination of military personnel stop in 1986 and vaccination was officially stopped in military recruits in 1990.

Smallpox Symptoms

Smallpox: Common Symptoms

When you're first exposed to the smallpox virus, you're in what's called the incubation period. You aren't contagious and you won't have symptoms for another 7 to 19 days. Symptoms of smallpox start with a high fever, headache, fatigue, body aches, and sometimes vomiting, all of which can last from two to four days. You may be contagious at this point.

A few days later, you will develop a flat rash that starts in your mouth and spreads, turning into raised bumps and pus-filled blisters that crust, scab, and fall off after about three weeks, leaving a pitted scar. You may also develop blisters in your nose and mouth.

You are most contagious once the rash begins, and you remain contagious until the last smallpox scab falls off.


Smallpox is an infection that's caused by the variola virus. It can be contracted from contact with another person, through the air in an enclosed building (rarely), or from contact with contaminated items such as blankets and clothes. There is no evidence that smallpox is spread by animals or insects.


Because smallpox has been eradicated for some time, most doctors wouldn't be able to tell that it's smallpox right away, which means it could spread quickly before a diagnosis could be determined.

The Centers for Disease Control and Prevention (CDC) would need to test the infected person's tissue to confirm smallpox. Just one confirmed case, anywhere in the world, would create an international health emergency.


There is no treatment per se for smallpox. The smallpox vaccine prevents people from getting smallpox and can be used if an outbreak would occur. If you get a smallpox vaccine within three days of being exposed to the virus, the vaccine may stop you from getting smallpox. If you do still develop the infection, it would likely be much less severe.

If you get the vaccine within four to seven days after exposure, it will probably give you some protection and again, would likely make the infection less severe. Once the rash has developed, the vaccine would be of no help.

Antivirals may also have a place in treating smallpox, but this remains unclear as of now. Treatment would likely most consist of keeping you comfortable, making sure you stay hydrated, and treating any symptoms or complications that might result, such as giving you antibiotics for a bacterial infection.

A Word From Verywell

The history of the rise and fall of smallpox is a success story for modern medicine and public health. Though almost all known stocks of the variola virus were destroyed once smallpox was proclaimed eradicated, the variola virus is stored at two locations for research purposes—one at the CDC in Atlanta, Georgia, and one in the Russian State Centre for Research on Virology and Biotechnology in the Russian Federation.

According to the CDC, it's possible but unlikely that the variola virus could be used in a bioterrorist attack, so there is a plan in place in the event that a smallpox emergency occurs. For example, there is enough smallpox vaccine available to vaccinate every single person in the United States should there be a smallpox outbreak or attack.

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