Smallpox is a contagious and often fatal infection caused by the variola (ver-e-O-luh) virus.


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Biological weapon

Edward Jenner

Vaccinia vaccine

Variola major

Varola minor


What Is Smallpox?

What do Queen Mary II of England, King Louis XV of France, and Czar Peter II of Russia have in common? Other than being royalty, they all died from smallpox, one of the deadliest diseases in history. This devastating illness first surfaced thousands of years ago, and many believe smallpox killed more people than all other diseases combined before it was wiped out in the late 1970s. The variola (from the Latin word varus, meaning "spotted") virus causes two types of smallpox: variola major and variola minor. Variola major (the type discussed in this chapter) is extremely serious and can be fatal in up to 30 percent of cases. The milder variola minor is fatal in less than 1 percent of patients.

How Common Is the Disease?

Thanks to the vaccine * developed by Edward Jenner in 1796 and the World Health Organization's (WHO) intensified immunization program begun in 1967, smallpox is no longer found in the world; the last naturally occurring case was reported in Somalia in Africa in 1977. Before this successful eradication program, the illness affected millions of people of all ages every year. Those who survived the severe period of infection often were left scarred or blinded.

Is It Contagious?

Smallpox is so contagious that just one infected person can launch an epidemic * . As soon as the first symptoms of the disease appear, an infected person can spread the virus by coughing, sneezing, or even talking. This expels tiny virus-packed drops of moisture into the air. When a healthy person breathes in these drops, the virus finds a new home. Less often, touching patients' sores or even just their bed linens or clothes can spread the infection. Smallpox is typically most contagious during the first week of illness. Outbreaks of the disease in a community have tended to occur at 2to 3-week intervals.

* vaccine (vak-SEEN) is a preparation of killed or weakened germs, or a part of a germ or product it produces, given to prevent or lessen the severity of the disease that can result if a person is exposed to the germ itself, Use of vaccines for this purpose is called Immunization.

* epidemic (eh-pih-DEH-mik) is an outbreak of disease, especially infectious disease, in which the number of cases suddenly becomes far greater than usual. Usually epidemics are outbreaks of diseases in specific regions, whereas worldwide epidemics are called pandemics.

Signs and Symptoms

Once the virus enters the body, it quickly reproduces and takes over healthy cells. An infected person usually is not even aware of the viral intruders for at least a week. Then the first wave of smallpox symptoms appears, often resembling those of a cold or the flu: fever, extreme tiredness, headache, backache, and occasionally, nausea (NAW-zee-uh) and vomiting. These symptoms can last up to a week. About 2 to 3 days after the onset of symptoms, a rash of red blisters or lesions * appears suddenly on the face, arms, and palms. Within a few days, the lesions fill with fluid and pus * and spread to other parts of the body, including the inside of the nose and mouth. The sores can expand and break open, causing pain. Eventually, scabs form and later fall off. During its early stages, smallpox can be confused with chicken pox, which is caused by a different virus (varicella zoster, var-uh-SEH-luh ZOS-ter). Chicken pox produces a much milder rash that usually develops on the body and is less prominent on the face, arms, and hands.

Ali Maow Maalin, of Somalia. He is the last person known to have contracted smallpox, in 1977. Science VU/CDC/Visuals Unlimited
Ali Maow Maalin, of Somalia. He is the last person known to have contracted smallpox, in 1977.
Science VU/CDC/Visuals Unlimited

How Do Doctors Make the Diagnosis?

Because smallpox was wiped out in the last quarter of the twentieth century, very few doctors practicing today have ever seen a case. With the heightened awareness of the possibility that smallpox could be used as a weapon in biological warfare * , doctors are being trained to recognize the disease. To make a diagnosis of smallpox, tests would be done on blood and fluid from a patient's lesions to identify the virus. To prevent a widespread outbreak, the patient most likely would be isolated, and those in close contact with the person would be vaccinated. If just one case of smallpox were diagnosed today, it could cause a public health emergency.

* lesions (LEE-zhuns) is a general term referring to sores or damaged or irregular areas of tissue.

* pus is a thick, creamy fluid, usually yellow or greenish in color, that forms at the site of an infection. Pus contains infection-fighting white cells and other substances.

* biological warfare is a method of waging war by using harmful microorganisms to purposely spread disease to many people.

* immunology (ih-myoo-NOL-uh-jee) is the science of the system of the body composed of specialized cells and the substances they produce that help protect the body against disease-causing germs.

Birth of a Vaccine

Edward Jenner often is called the father of modern immunology * because of his major contribution to ending smallpox. As an English country doctor, Jenner was fascinated that milkmaids exposed to cowpox (a disease that affects cows and is caused by a virus similar to variola) did not contract smallpox. He developed a vaccine containing live cowpox virus and injected it into an 8-year-old boy. The boy did not contract smallpox, and vaccinations for the disease quickly became standard. Following Jenner's discovery, fatalities from smallpox dropped significantly. Jenner believed that his vaccine provided lifelong immunity to the disease. It is now thought, however, that the vaccine may not protect people for more than 10 years.

What Is the Treatment for Smallpox?

There is no known cure for smallpox. Receiving the smallpox vaccine within 4 days of being exposed to someone who has the disease may prevent infection or lessen symptoms. Scientists are looking for new medicines as possible treatments for the disease. Public health agencies recommend that patients who have symptoms of smallpox be isolated immediately—either in a special unit of a hospital or at home—so that the infection will not spread to others. Health care workers are advised to take careful precautions when treating these patients. In the absence of a cure, treatment focuses on easing symptoms and preventing further infections. Patients may receive intravenous fluids (fluids injected directly into a vein), pain relievers, and antibiotics (to combat bacterial infections that can develop in the open sores) while the disease runs its course.

Though most often spread by drops of moisture expelled through an infected person's cough, smallpox may also be acquired through direct contact with the person's sores. Phototake
Though most often spread by drops of moisture expelled through an infected person's cough, smallpox may also be acquired through direct contact with the person's sores.

What to Expect

Smallpox infection can last from 3 to 4 weeks or until the last scabs fall off. The lesions often leave behind deep, pitted scars. When smallpox is fatal, patients usually die during the second week of illness. Smallpox can lead to serious complications, including these:

  • hemorrhagic (heh-muh-RAH-jik) smallpox (which is associated with bleeding in the skin and body membranes)
  • malignant smallpox (in which the sores are flat and close together)
  • blindness
  • bacterial infections
  • pneumonia *
  • encephalitis *

How Can Smallpox Be Prevented?

Widespread vaccination in the United States for smallpox ended in 1972. In 1980 WHO declared the disease eradicated. It is unknown how long vaccine-generated immunity * lasts. Experts believe that it prevents infection for at least 10 years, but scientists think that few people in the world today are still immune to smallpox.

Today there are two official facilities that store samples of the virus: the U.S. Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, and the Russian State Research Center of Virology and Biotechnology in Koltsovo. In the unlikely event that bioterrrorists were to get access to any of these stored samples, it is possible that they might use the virus to launch a biological attack. If this were to happen, vaccines would be in high demand. To prepare for such a potential emergency, mass production of the vaccine is under way in the United States.

* pneumonia (nu-MO-nyah) is inflammation of the lung.

* encephalitis (en-seh-fuh-LYE-tis) is an inflammation of the brain, usually caused by a viral infection.

* immunity (ih-MYOON-uh-tee) is the condition of being protected against an infectious disease. Immunity often develops after a germ is introduced to the body. One type of immunity occurs when the body makes special protein molecules called antibodies to fight the disease-causing germ. The next time that germ enters the body, the antibodies quickly attack it, usually preventing the germ from causing disease.

Owing to possible side effects of the smallpox vaccine, the CDC suggests that it be given only to those at greatest risk of being exposed to the virus, including military personnel and "first responders," for example, medical care providers, law enforcement personnel, and laboratory workers. About one in a million people who are vaccinated die from the effects of the vaccine, and a small percentage experience scarring or serious infections.

See also
Public Health
Varicella (Chicken Pox) and Herpes Zoster (Shingles)



Center for Civilian Biodefense Strategies, Johns Hopkins University, 111 Market Place, Suite 830, Baltimore, MD 21202. The Center for Civilian Biodefense Strategies has fact sheets on smallpox and its place in bioterrorism.
Telephone 410-223-1667

U.S. Centers for Disease Control and Prevention (CDC), 1600 Clifton Road, Atlanta, GA 30333. The CDC provides fact sheets and vaccine information on smallpox.
Telephone 800-311-3435

World Health Organization (WHO), Avenue Appia 20, 1211 Geneva 27, Switzerland. The WHO website has links to fact sheets and information on the prevention and control of smallpox.
Telephone 011-41-22-791-2111

Also read article about Smallpox from Wikipedia

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