Symptoms of Smallpox

Early symptoms of smallpox are similar to the flu, progressing to a rash a few days later that then turns into deep sores that fill with fluid. These blisters ooze, crust, and scab over, eventually falling off and leaving scars. There is no cure or treatment for smallpox, but thankfully it was eradicated in 1980, meaning that it no longer naturally occurs anywhere in the world.

smallpox symptoms
Illustration by Verywell

Frequent Symptoms

Because it's contagious, smallpox is generally transmitted by face-to-face contact with infected people. It can also be spread by having contact with contaminated clothing or bedding and in a small number of cases, through the air.

If a person does become infected with smallpox, there is an incubation period of seven to 19 days before symptoms begin to develop.

While it spreads very easily from person to person, the initial symptoms are flu-like and may include:

  • High fever
  • Fatigue
  • A headache​
  • A backache
  • Vomiting

A few days later, flat red sores or spots will begin to appear on your face, hands, and arms, and eventually on the trunk of your body. Within a few days, many of the sores will begin to turn into small blisters filled with fluid. The fluid will then turn into pus. Over time, the sores will scab and fall off, leaving deep, pitted scars.


If you're pregnant or have a suppressed immune system, getting smallpox can be more serious and potentially fatal.

In the past, roughly one in three people who contracted smallpox died.

Recovering from smallpox also left many people with permanent scars and sometimes even some disfigurement from losing nasal or facial tissue. Because sores often form on and around the eyes, eye infections and other eye complications occurred. Less commonly, people went blind.

While the vaccination against smallpox is extremely effective for the disease's prevention, it's associated with known side effects that range from mild effects like soreness and slight fever to serious side effects like an infection in your heart or brain.

These potentially serious side effects are why the general population isn't routinely vaccinated anymore. In the event that a smallpox outbreak or epidemic should occur, the Centers for Disease Control and Prevention (CDC) does have enough vaccine available to inoculate every person in the United States.

When to See a Healthcare Provider

No one has had smallpox in the United States since 1949, and no one in the world has had it since 1978, so if people were to contract it now it would either be due to the use of the variola virus as a biological weapon or from exposure to the virus in the environment.

For instance, in Siberia, Russia, global warming is causing many areas that were previously frozen to melt, potentially exposing graveyards with corpses containing the variola virus.

It would be difficult to know you have smallpox until the rash forms and you start developing deep fluid-filled sores since the early symptoms are similar to that of the flu.

If you develop any suspicious rash, no matter what you think it is, you should see your healthcare provider. If your practitioner suspects smallpox, you would be isolated to prevent spread and your healthcare provider would work with the CDC to diagnose and treat you. This would also signal a public health emergency for which the CDC is ready to enact a plan to respond to an outbreak or a bioterrorism threat.

Frequently Asked Questions

  • What are the signs and symptoms of smallpox?

    The first signs of smallpox are typically fever and vomiting. This is followed soon after by the appearance of mouth ulcers and a rapidly spreading rash. The rash will quickly form fluid-filled blisters, usually starting on the face and spreading to the trunk and extremities. After the blisters rupture, they quickly scab over and eventually fall off, leaving a scar.

  • How long after exposure do smallpox symptoms appear?

    The initial prodromal symptoms of smallpox typically develop 10 to 14 days after exposure and will persist for two to four days. Thereafter, mouth ulcers will be the first physical sign followed by the rapid onset of rash 24 to 48 hours later. From start to finish, most cases of smallpox resolve within five weeks.

  • How long is smallpox contagious?

    Smallpox is not contagious during either the 10- to 14-day incubation period or the initial prodromal phase. It is only with the appearance of rash that the virus can be spread to others (usually from person to person but also through contaminated objects). Smallpox is considered contagious until the last dried scab falls off.

  • Can smallpox kill you?

    Smallpox has a 30% risk of death. The risk is greatest with severe forms of the disease, called malignant-type smallpox and hemorrhagic smallpox, both of which are typically fatal. Death is often the result of severe dehydration caused by the massive loss of body fluids, leading to shock, coma, and multi-organ failure.

  • When was the last reported case of smallpox?

    The last natural outbreak of smallpox occurred in the United States in 1949. The last natural case of smallpox was reported in Somalia in 1977. In 1980, the World Health Assembly declared smallpox eradicated, and no cases have been seen since.

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Centers for Disease Control and Prevention. Smallpox.

  3. Regan TD, Norton SA. The scarring mechanism of smallpox. J Am Acad Dermatol. 2004;50(4):591-594. doi:10.1016/j.jaad.2003.10.672

  4. Centers for Disease Control and Prevention. Who Should Get Vaccination.

  5. Simonsen KA, Snowden J. Smallpox. In: StatPearls [Internet].

  6. Centers for Disease Control and Prevention. Smallpox: transmission.

  7. Food and Drug Administration. Smallpox.

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  9. Centers for Disease Control and Prevention. History of smallpox.

By Heather L. Brannon, MD
Heather L. Brannon, MD, is a family practice physician in Mauldin, South Carolina. She has been in practice for over 20 years.