Smallpox is caused by infection with the variola virus. Symptoms occur 7 to 17 days following exposure. Initial symptoms include: fatigue, high fever, and head and back pain. A characteristic rash - appearing most commonly on the face, arms and legs - occurs early in the course of the disease. The rash starts with red flat lesions that become pus-filled and then begin to crust over in the second week. Most patients with smallpox recover but are left with severe residual scarring; the disease is lethal in up to 30% of all cases. There is no treatment for smallpox, although studies looking at recently developed antiviral drugs are underway.
- The last naturally acquired case of smallpox occurred in 1977. The last case of smallpox acquired via lab exposure occurred in 1978. The only declared stocks of smallpox virus are located in Atlanta at the Centers for Disease Control and Prevention (CDC) and in Russia.
- In the U.S., routine smallpox vaccination ended in 1972. The vaccine contains a closely related live virus known as vaccinia, which is poked under the skin with a special two-pronged needle. In many people who receive the vaccine, a significant localized reaction occurs. In people with suppressed immunity, severe vaccine reactions and death can occur from the vaccine. The vaccine also causes problems for people with skin disorders, particularly eczema. Some of these reactions can be treated with infusions of special immune globulins.
- Because the disease has been eradicated, the vaccine is no longer available to the general public. Due to the side effects that may result, routine use of the vaccine has been discouraged. The CDC maintains a supply of vaccine that is available on an emergency basis.
- Although a smallpox attack is not expected, the events following 9/11 have heightened awareness to the possibility of an act of bioterrorism that could involve smallpox.
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Smallpox is spread from one person to another by face-to-face contact. When a susceptible person is in the presence of saliva droplets from an infected person, the virus is transferred. People with smallpox are most infectious during the early course of the disease when the amount of virus present in their saliva is highest.
Patients with suspected or confirmed smallpox are capable of spreading the infection. These individuals should be placed in isolation in order to control transmission of the virus. In people exposed to smallpox, the vaccine can lessen the severity or even prevent the illness if given within 4 days of exposure. There is no proven treatment for smallpox.
- Contaminated clothes and bedding can also spread the disease. These items should be autoclaved (steam sterilized) or washed in bleach and hot water. Disinfectants like bleach and quaternary ammonia can be used for decontaminating surfaces.
- The virus that causes smallpox is fragile. In the event of an aerosol release, the virus will be inactivated within 1 to 2 days.
Since the risk of naturally contracting smallpox in the U.S. is very low, any suspected case should be reported to health authorities and should prompt an investigation into the possibility of bioterrorism. The intentional release of a biological agent, like smallpox, constitutes an act of bioterrorism. If a person thinks they have been exposed to a biological incident or they suspect a biological threat is planned, they should contact their local health department and/or their local police department. Either of these agencies will promptly notify the FBI, which is responsible for coordinating interagency investigation of bioterrorism.
During the events of 9/11, one of the hospital residents lost a brother in the plane that crashed into the Pentagon. He's exhibiting a lot of rage and his work is suffering. When a senior physician tries to talk about his problem, the resident blows up. After the resident calms down, he talks to the physician about his anger and also, his feelings of impotence in not being able to help patients if there were a disaster - like a bioterrorist attack. The senior physician advises the resident that he must do something proactive - something that will help. The resident does some research and finds out about an upcoming clinical trial to test smallpox vaccine. The doctor and the resident apply to the National Institutes of Health (NIH) to become investigators and enroll their hospital as a study site.
- Page last reviewed: February 23, 2011
- Page last updated: February 14, 2017
- Content source:
- Centers for Disease Control and Prevention
- Page maintained by: Division of Public Affairs (DPA), Office of the Associate Director for Communication (OADC)