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Smallpox is a highly contagious disease that is caused by a virus. It infected many human beings for thousands of years and led to uncountable deaths. The symptoms of this infection are severe and cause extreme discomfort to the affected person. There is still no cure available for smallpox, but after the advent of its vaccine, it had been eradicated worldwide by the year 1980. Some samples of smallpox have only been reserved for research purposes. 


Smallpox is an infection caused by the variola virus. The virus can spread via different modes of transmission. One of the common ways of its spread is the transfer of the virus from one infected person to another. It transfers if you come in direct contact with aerosols or cough droplets from an infected person. In rare cases, it can also spread indirectly through contaminated air. For example, it can spread from one room to another if there is a common ventilation channel.

Another mode of transmission is sharing used products such as clothing items, pillow covers, bedding, toothbrushes, etc. The spread of infection through this way is rare, but it can happen. Therefore necessary precautions would still be required. 


There were two common types of the variola virus. They were known as variola major and variola minor. Variola major was the most lethal form of this virus. Almost 30% of the people died after being infected by this virus. Variola minor was comparatively less fatal than its counterpart. It was estimated that nearly 1% of the people died who were infected from this type.

There were two other rare forms of this virus as well. They were known as hemorrhagic and malignant types. The infection from either of these types was rare, but if it happened, it led to severe disease and complications.

Risk Factors And Epidemiology

Before the advent of the smallpox vaccine, children, older adults, and those with weakened immune systems were at the highest risk of developing a fatal infection. Coming in contact with an infected person, sharing the same room with them, or sharing everyday items were other risk factors. After eradicating this virus, the risk of developing this disease is very low. It may only happen if someone is involved in laboratory or research work involving the virus.

Smallpox was one of the most deadly infections in the world a few centuries ago. Once its vaccine was made, World Health Organization (WHO) launched global campaigns for its vaccination and maintained strict rules to limit the spread of this virus. The last recorded case of smallpox occurred in Somalia in 1977. By the end of 1980, WHO announced the complete eradication of this virus on a global scale. 

Signs And Symptoms

Once the virus has entered your system, it takes an incubation period of 7 to 17 days, during which it develops and propagates. You are not contagious during this period and remain asymptomatic. As soon as the incubation period approaches its end, the symptoms of this infection start to develop, including fever, headache, fatigue, weakness, and back pain.

After two or three days, these symptoms begin to fade away, and a rash appears, which usually starts from the face. This rash spreads to other parts of the body, including the neck, arms, legs, and trunk. These rashes evolve into fluid-filled blisters within a few days, which get filled with pus later. After some time, these blisters form scabs and fall off, leaving deep scars. During this whole period, an infected person can easily spread the infections to others. 


If a case of smallpox were to occur in the present world, the diagnostic criteria defined by CDC would divide the suspected patients into low, medium, and high-risk groups. A detailed history of their symptoms would be necessary, along with a physical examination of the skin lesions. Blood work, lesion samples, and tonsils swabs will be necessary. The final conformational diagnosis of smallpox would be made using a polymerase chain reaction (PCR) test. A false-positive test result could have major consequences. Therefore, all symptoms and lab results would be taken into account before confirming the diagnosis of smallpox. 

Differential Diagnosis

Symptoms of smallpox can resemble the symptoms of a few other diseases such as chickenpox, herpes zoster, erythema multiforme, monkeypox, Kawasaki disease, rubella, etc. All possible conditions should be tested for and ruled out before announcing a confirmed diagnosis of smallpox. 


There is no known cure for smallpox yet. Tecovirimat is an antiviral drug that has been studied for its effectiveness against the virus, but it is still being tested. Supportive care is the only thing that can be done if a person gets infected by smallpox. Rest and fluid intake are recommended.

Analgesics may be prescribed to reduce pain. Antibiotics are given to reduce secondary complications associated with skin lesions. No other drugs can cure the infection itself. 


Prognosis varies depending on the type of virus you’re infected with. The incidence of death by variola major infection is around 10%. The fatality rate is much higher if you get infected with other rare forms of the virus. 


The prevention of smallpox has been achieved by its vaccine, which helped eradicate this virus. In these times, the vaccine is not administered as a precautionary measure because of its potential complications in those with weakened immune systems. If an outbreak of smallpox were to occur, the suspected person would be kept in strict isolation. Vaccination can be done in the early few days of infection to reduce mortality risk.

Our clinical experts continually monitor the health and medical content posted on CURA4U, and we update our blogs and articles when new information becomes available. Last reviewed by Dr.Saad Zia on May 29, 2023.



Smallpox (who.int)


Smallpox | Definition, History, Vaccine, & Facts | Britannica