Posted August 20, 2022 by Anusha ‐ 3 min read

Smallpox is a contagious disease caused by a virus that’s no longer found in nature. For centuries, smallpox killed millions of people around the world. But thanks to global immunization programs, the deadly infectious disease was wiped out in the late 1970s. Today, scientists keep only a small amount of the virus alive under tightly controlled conditions in the U.S. and Russia for medical research.


Smallpox gets its name from its most common sign of the disease: small blisters that pop up on the face, arms, and body, and fill up with pus.

Other symptoms include:

  • Flu-like fatigue

  • Headache

  • Body aches

  • Intense back pain

  • Some vomiting

  • High fever

  • Mouth sores and blisters that spread the virus into the throat

  • A skin rash that gets worse in a typical pattern:

  • The rash starts with flat red sores that become raised bumps a few days later.

  • The bumps turn into fluid-filled blisters.

  • The blisters fill with pus.

  • They crust over, usually in the second week of smallpox.

  • Scabs form over the blisters and then fall off, usually in the third week of the disease. They can cause permanent scars.

  • Blindness can happen when blisters form near the eyes.


  • The variola virus causes it. There are two forms of the virus.

  • The more dangerous form, variola major, led to smallpox disease that killed about 30% of people who were infected.

  • Variola minor caused a less deadly type that killed about 1% of those who got it.

  • Two forms of smallpox were more deadly than the common strain: Hemorrhagic and malignant.

  • Hemorrhagic smallpox tended to affect adults, including pregnant women, not children.

  • People had more serious symptoms, including fever, pain, and headaches, and they leaked blood from their blisters and mucous membranes.

  • People usually died of blood poisoning within a week.

  • Malignant smallpox tended to affect children, not adults.

  • Instead of raised blisters, people developed flat lesions that merged on the skin surface.

  • Most people who got this form of smallpox also died of blood poisoning.

How it transmits?

  • By breathing in the virus during close, face-to-face contact with an infected person. It usually spreads through drops of saliva when the person coughs, sneezes, or speaks.

  • By handling the clothes or sheets of an infected person or coming into contact with their body fluids.

  • Very rarely, smallpox has spread among people in small, enclosed spaces, probably through air in the ventilation system. Animals and insects don’t spread the disease.

  • If the virus were spread through an act of terrorism. This is a rare possibility, but in case it happens, governments around the world have stockpiled smallpox vaccines.


  • Because smallpox hasn’t been diagnosed in decades, it’s likely that doctors wouldn’t recognize the disease in patients right away.

  • It’s possible to diagnose the condition by testing a sample of tissue taken from a smallpox blister.

  • A single diagnosis would be considered a worldwide health emergency.


  • There’s only one known drug that can treat smallpox.

  • The drug tecovirimat (TPOXX) was approved in 2018 for the treatment of smallpox should someone show symptoms of the virus.

  • The drug cidofovir has also worked well in early studies.

  • Getting the vaccine within 3 to 4 days of contact with the virus may make the disease less severe or may help prevent it.

  • Beyond that, medical care aims to ease symptoms like fever and body aches, and control any other illnesses that a person can get when their immune system is weak.

  • Antibiotics can help if someone gets a bacterial infection while they have smallpox.

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