Smallpox is a serious infectious disease caused by the variola virus. It is contagious, and causes a fever and a distinctive, progressive skin rash. The World Health Assembly declared the world free of smallpox on May 8, 1980, and no cases of naturally occurring smallpox have happened since 1977.
Most people who developed smallpox recovered, though they were left with scars on many parts of their body, especially their faces. Some were left blind. About 30% of people with the disease died.
We do not still vaccinate for smallpox. Routine vaccination against smallpox disease ended in the U.S. in the early 1970s.
What Are Symptoms of Smallpox?
The first symptoms of smallpox last from 2 to 4 days and include:
- High fever
- Head and body aches
- Sometimes vomiting
This next stage of smallpox lasts about 4 days, is when the patient is most contagious, and symptoms include:
- Continued fever
- A rash that starts as small red spots on the tongue and in the mouth
- Spots change into sores that break open and spread large amounts of the virus into the mouth and throat
- When the mouth sores start breaking down, a skin rash appears, starting on the face and spreading to the arms and legs, and then to the hands and feet
- The rash usually spreads all over the body within 24 hours
- As the rash appears, the fever subsides
- By the fourth day, the skin sores fill with a thick, opaque fluid and often have a dent in the center
- Once the skin sores fill with fluid, fever again rise and remain high until scabs form over the bumps
This next stage of smallpox lasts about 10 days, and symptoms include:
- Sores become sharply raised, round and firm to the touch (pustules)
- After about 5 days, pustules form a crust and then scab
- By the end of the second week after the rash appears, most of the sores have scabbed ove
In the last stage of smallpox, which lasts about 6 days, the scabs begin to fall off, leaving marks on the skin. Most scabs will fall off about 3 weeks after the rash appears, and by 4 weeks all scabs have fallen off and a person is no longer contagious.
What Causes Smallpox?
Smallpox is caused by the variola virus. Before smallpox was eradicated, it was mostly spread by direct and prolonged face-to-face contact. The illness is contagious once sores first appear in the mouth and throat. The virus was transmitted when an infected and contagious person coughed or sneezed and spread droplets into the air to other people nearby.
The scabs and fluid in the sores also contained the virus, which could be spread when the fluid contaminated bedding or clothing used by the infected person.
In rare cases, smallpox can spread through the air in an enclosed setting.
How Is Smallpox Diagnosed?
Smallpox was eradicated in 1979, so most doctors have not seen a case of smallpox and may not recognize the characteristic lesions.
The Centers for Disease Control (CDC) proposed clinical diagnostic criteria for smallpox in the event the variola virus is used as a bioterrorism agent.
Testing for smallpox is only performed in specialized laboratories and doctors would work with local and state health departments to determine the appropriate handling of specimens.
The laboratory criteria to diagnose smallpox includes:
- Isolation of smallpox (variola) virus from a clinical specimen (WHO Smallpox Reference Laboratory or laboratory with appropriate reference capabilities) with variola PCR confirmation
What Is the Treatment for Smallpox?
If a smallpox outbreak were to occur, public health officials would use the smallpox vaccine to control it.
Some antiviral drugs may help treat smallpox but there is no smallpox treatment that has been tested in people who are sick with the disease and proven effective.
Antiviral medications that might be used to treat smallpox include:
- Tecovirimat (TPOXX)
- Food and Drug Administration (FDA) approved for treatment of smallpox
- Has been shown effective in lab tests and animal tests
- Cidofovir and brincidofovir
- Not FDA approved to treat the variola virus that causes smallpox but might be used for isolated cases or during an outbreak under an appropriate regulatory mechanism (such as an investigational new drug [IND] protocol or Emergency Use Authorization)
- Have been shown to stop the grown of the variola virus in lab tests and are effective in treating animals with similar diseases to smallpox
These drugs have not been tested in people sick with smallpox, so it is unknown if a person with smallpox would benefit from treatment with them.
How Do You Prevent Smallpox?
Smallpox can be prevented by the smallpox vaccine (also called the vaccinia virus vaccine).
The smallpox vaccine is not currently available to the general public because smallpox has been eradicated, and the virus no longer exists in nature. Only lab workers who work with the virus that causes smallpox or other viruses similar to it should receive the smallpox vaccine.
If a smallpox outbreak was to occur, such as from a bioterrorism attack, there is enough smallpox vaccine stockpiled to vaccinate every person in the U.S. In the event of a smallpox outbreak, public health officials would determine who needed to get the vaccine.
The Strategic National Stockpile (SNS) has three smallpox vaccines:
- ACAM2000 and Jynneos (other brand names include Imvamune or Imvanex) are the only two licensed smallpox vaccines in the U.S.
- Aventis Pasteur Smallpox Vaccine (APSV) is an investigational vaccine that may be used in a smallpox emergency
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