What You Need to Know About Smallpox

A Highly Contagious and Potentially Deadly Virus

The smallpox virus.
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Smallpox is a contagious and potentially deadly virus caused by the Variola major virus. Until its eradication, there were two forms of the disease worldwide: Variola major and Variola minor. The Variola major is the more deadly form of the disease whereas Variola minor is a much milder form of the disease.

With successful worldwide immunization, the last reported case of smallpox was in 1977.

In 1980, the World Health Organization (WHO) declared the eradication of smallpox. There is no cure or treatment for smallpox. While the vaccination against smallpox is extremely effective for the disease's prevention, it is associated with known side effects that range from mild effects like soreness and slight fever to serious side effects like the development of a vaccinia rash.

The Spread and Symptoms=

Because it is highly contagious, smallpox can be transmitted by face-to-face contact with infected people. It can also be spread through the air and contact with contaminated clothing or bedding. If a person does become infected with smallpox, there is an incubation period of 7 to 17 days before symptoms begin to develop. While it spreads very easily from person to person, the initial symptoms are flu-like and include:

  • High fever
  • Fatigue
  • Headache
  • Backache
  • Vomiting

A few days later, flat, red sores or spots will begin to appear on your face, hands, and arms.

Later, they will appear 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.


Smallpox has no proven treatment. Intravenous fluids and medicine to control the fever and pain may be administered.

Antibiotics may be used for any secondary bacterial infection that occurs. An injection of the smallpox vaccine may lessen the severity or length of the illness.


To prevent the spread of smallpox, people who have been infected are kept isolated from other people. The close contacts of the infected person are vaccinated with the smallpox vaccine to prevent the spread of the disease.

The smallpox vaccine can help prevent the infection and may help those who have been exposed to the disease if they are vaccinated within four days of exposure to the virus. The vaccine may cause a low fever, swollen glands, and redness at the site of the vaccination. It does, however, cause life-threatening complications in people who have skin or immune disorders.

If you were vaccinated as a child, you may have partial immunity against the more serious complications of smallpox. If an outbreak did occur, you would still likely be vaccinated if you came into direct contact with an infected person.


National Institute of Allergy and Infectious Diseases


Centers for Disease Control and Prevention

The Nemours Foundation

The Mayo Clinic

World Health Organization