Smallpox Overview

Smallpox—though now eradicated—was a highly contagious infectious disease that killed about 30% of those who contracted the virus. The disease caused a high fever and a disfiguring rash, and often left survivors with permanent scars or blindness.

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Smallpox is an ancient—and highly contagious—virus first discovered thousands of years ago. Initially, it prompted illness and death during global outbreaks that would take place from time to time. Due to the availability of vaccinations, the variola virus (AKA the smallpox virus) has been eradicated. There hasn't been a smallpox outbreak in the United States since 1949. In fact, the last naturally occurring case was diagnosed in 1977, according to the Centers for Disease Control (CDC).

In 1980, the World Health Organization (WHO) announced that smallpox has been eradicated globally, but researchers remain focused on developing vaccines, drugs, and diagnostic tests to protect people against smallpox, in the event that it is used as an agent of bioterrorism.

What Is It?

Smallpox is caused by two virus variants, variola major and variola minor. Before it was eradicated, it was considered to be a very serious infectious disease and was accompanied by fever and a distinctive, progressive skin rash, according to the CDC.

While most smallpox patients ultimately recovered from the virus, three out of every 10 people with the disease died, according to the CDC. Many smallpox survivors have permanent scars over large areas of their body, especially their faces, and some lost their vision.


Named for the Latin word for "spotted"—since smallpox patients develop raised bumps— smallpox is classified in two ways: variola major and variola minor. Variola major is considered to be the most severe form and is accompanied with a high fever and rashes on more places on the body. There are four subtypes of variola major: ordinary, modified, flat, and hemorrhagic. Variola minor is more uncommon and less severe and lead to death rates of one percent or less, according to the Food & Drug Administration (FDA).


Generally speaking, smallpox symptoms begin 12 to 14 days after you've been exposed to the virus, starting with two to three days of high fever, severe headache, and backache. This is followed by a rash that progresses to raised areas of skin, one to two days after the rash appears. On the fourth or fifth day, fluid-filled blisters appear and, generally, scabs form within two weeks.

It's important to note that a smallpox rash tends to begin with small red spots on the tongue and in the mouth, before it spreads on the face, forearms and legs. Firm, round lesions may then appear on the palms and soles of the feet as well, according to the CDC.


Smallpox is a virus that is spread among humans via coughing or sneezing. There is no evidence that smallpox can be spread by insects or animals, according to the CDC, and it has rarely spread through the air.

Before vaccinations eradicated smallpox, it was generally spread via direct and fairly prolonged face-to-face contact between people, according to the CDC. In fact, the most contagious time for smallpox to spread is when sores appear in the mouth and throat. At that time, bedding and clothing can become contaminated as well. Anyone with smallpox remains contagious until the last smallpox scab falls off.


To definitively diagnose smallpox, a tissue sample from a skin lesion would need to be taken from an infected person and analyzed. At that point, experts would be called in to make sure the lesions aren't stemming from the chickenpox virus, according to the CDC.

However, even one case of smallpox would prompt an international health emergency, according to the CDC, and infectious disease experts are trained to act immediately if this should ever occur.


While some antiviral drugs may help treat smallpox disease, there is no proven, effective treatment for smallpox that has been tested in people who are sick with the disease, according to the CDC.


The only way to prevent smallpox is to be vaccinated against it. Fun fact: A British doctor developed the smallpox vaccine in 1796, making it the first vaccine to be developed to protect against a contagious disease.

Made from a poxvirus called vaccinia, that is similar to smallpox but not as harmful, there are two licensed smallpox vaccines in the United States, and one that may be used in case of a smallpox emergency, according to the CDC.

Since 1972, the smallpox vaccine has not been available to the general public because smallpox has been eradicated, and the virus no longer exists in nature. However, if a smallpox outbreak were to occur, there is enough smallpox vaccine to vaccinate every person in the United States, according to the CDC.

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