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Smallpox is a contagious disease caused by the variola virus that causes a skin rash, pustules and scabs. It is also called variola.

Smallpox killed millions of people worldwide in the past, but was eradicated by 1978 through an immunization program administered by the World Health Organization (an organization of the United Nations concerned with worldwide public health). Routine childhood vaccinations for the disease ended in 1972 in the United States.

In recent years, there has been renewed interest in smallpox because of growing terrorist activity worldwide. Smallpox is among the diseases that could be spread as part of a bioterrorist attack.

There are two types of smallpox, variola minor (a less severe form of the disease) and variola major (a more severe form of the disease). Variola major results in death in about 30 percent of cases, according to the U.S. Centers for Disease Control and Prevention (CDC).

Smallpox is usually spread by having face-to-face contact with an infected person. The virus is contained in air droplets emitted when a person coughs, sneezes or talks.

Smallpox usually starts with flu-like symptoms, such as a high fever and headache. A rash develops on the face and then spreads to the arms, legs, hands and feet. Blisters and pustules form on the skin in later stages of the disease.

Smallpox is diagnosed during a physical examination that includes a medical history and list of medications. The CDC has issued guidelines that assist physicians in recognizing the signs and symptoms of smallpox.

There is no cure for smallpox. Most patients receive supportive therapy, such as intravenous fluids and fever and pain control.

The best way to prevent smallpox is to receive a vaccination. Currently, only certain people in the U.S. receive the vaccine, such as select military personnel and healthcare workers. The United States has an adequate supply of the vaccine in the event of an emergency.

About smallpox
Smallpox is a highly contagious and sometimes fatal disease caused by the variola virus and characterized by a skin rash. It is also called variola.

The word smallpox is derived from the Latin word for “spotted” and refers to the raised bumps that appear on an infected person.

Smallpox used to kill millions of people worldwide and was once considered a major health problem. In 1967, the World Health Organization (WHO [an organization of the United Nations concerned with worldwide public health]) embarked on a global immunization campaign in an effort to eradicate the disease. The organization’s efforts were successful and the last naturally occurring case of smallpox was reported in 1977 in Somalia.

Because the risk of having an adverse reaction to the vaccine was higher than the risk of developing smallpox, routine vaccination for the disease ended in 1972 in the United States. In 1980, the WHO declared that smallpox had been eradicated and the vaccine was discontinued worldwide.

However, smallpox has resurfaced as a health concern in recent years due to concerns about bioterrorism (the use of bacteria or viruses to cause illness and spread fear). Smallpox and anthrax (a disease caused by the spores of a bacteria called Bacillus anthracis) are often cited as diseases that could be spread as part of a bioterrorist attack.

There are still stocks of the smallpox virus kept for research purposes in laboratories in the United States and Russia. It is feared that the virus could be obtained by terrorists and used to spread the disease. Because the effects of the vaccine wear off over time, most people (even those previously vaccinated) may be susceptible to smallpox.

Types and differences of smallpox
There are two clinical forms of smallpox:

Variola minor. This is a much less common and less severe form of the disease with a low death rate (less than 1 percent), according to the U.S. Centers for Disease Control and Prevention (CDC).
Variola major. This is the most common form of smallpox, and is accompanied by a more extensive skin rash and higher fever. About 30 percent of variola major cases are fatal, according to the CDC. There are four types of variola major:

Ordinary. This accounts for more than 90 percent of the cases, according to the CDC.
Modified. A less severe type which occurs most often in previously vaccinated people. It is characterized by rapid onset and subsequent healing of the lesions.
Hemorrhagic. Occurs more frequently in adults and pregnant women. It is characterized by a red, pinpoint rash and bleeding in the skin and mucous membranes.
Flat (malignant). Occurs more frequently in children. It is characterized by lesions that are velvety and never become filled with pus. Eventually, the skin takes on a rubbery appearance.

More than 95 percent of patients who develop the hemorrhagic or flat types of smallpox die, according to the American Academy of Dermatology.

Risk factors and causes of smallpox
Smallpox is caused by the variola virus which, when magnified, looks like rectangles with a deeply patterned surface. They are sometimes called bricks.

Smallpox is usually spread through personal contact with an infected individual. The virus is transmitted through air droplets, spread when a person cought, sneezes or even talks.

In rare cases, airborne particles may be spread through a building’s ventilation system. Smallpox can also be spread through contaminated clothing and bedding, although the risk of infection from these sources is small.

Inside the body, the virus begins to replicate, beginning in the lymph nodes and spreading to the spleen and bone marrow. The virus eventually settles in the mucous membraines of the nose and throat, as well as the blood vessels in the skin. Patients are most contagious when lesions in the mouth slough off and large amounts of the virus are released into the saliva.

The incubation period is about two weeks from the time of infection to when symptoms become apparent. At first, only a few people develop the disease, but 14 days later, more people develop it and, in another two weeks, additional cases emerge.

Signs and symptoms of smallpox
There are several stages of smallpox. The signs and symptoms that accompany each stage include:

Incubation stage. The incubation period may last from seven to 17 days after a person becomes infected with the smallpox virus, but usually averages between 12 to 14 days. During this stage, patients feel well, do not experience symptoms and are not contagious.
Prodrome stage. This stage typically lasts between two to four days. Patients, who may be contagious, are usually too sick to conduct normal activities. Symptoms are experienced suddenly and may include:

High fever (usually between 101 to 104 degrees Fahrenheit [38.3 to 40 degrees Celsius])
General sick feeling (malaise)
Headache
Severe fatigue (prostration)
Severe back pain
Abdominal pain
Vomiting
Delirium

Early rash stage. Patients are most contagious during this stage, which begins with the development of small, red spots on the throat or the roof of the mouth which may be unnoticeable. The spots develop into lesions that break open and spread large amounts of the virus into the mouth and throat. A skin rash develops, starting on the face and spreading to the arms and legs and then to the hands and feet. The rash usually spreads to all parts of the body within 24 hours. As the rash appears, the fever may fall and patients may begin to feel better. Within a few days, the lesions turn into small blisters filled with fluid (vesicles) that often have a depression in the center that looks like a bellybutton. Fever may rise again and remain high until scabs form.
Pustular rash stage. This lasts about five days. Patients are still contagious. The vesicles turn into pustules (small, inflamed, pus-filled, blister-like lesions on the skin surface). Patients sometimes describe the pustules as feeling like BB pellets embedded in the skin.
Pustules and scab stage. The pustules erupt, begin to form a crust and then a scab. This stage can be very painful. Most of the sores have scabbed over by the second week after the rash appears. Patients are still contagious during this stage.
Resolving scab stage. The scabs begin to fall off and leave marks on the skin that may eventually turn into pitted scars. Most scabs fall off three weeks after the rash appears.
Scabs resolved. Patients are no longer contagious after all of the scabs fall off.

Diagnosis and treatment for smallpox
Smallpox is diagnosed by a physician during a physical exam that includes a medical history and complete list of medications.

The U.S. Centers for Disease Control and Prevention (CDC) issued guidelines that assist physicians in recognizing the signs and symptoms of smallpox. Patients may be examined by health professionals who have received special training in this area.

The CDC guidelines contain information about how to distinguish smallpox from chickenpox, a disease that commonly affects children and is caused by a virus (varicella zoster). Differences between the two diseases include:

Mortality. Unlike smallpox, chickenpox is rarely fatal.
Lesions. Chickenpox lesions are more superficial than those associated with smallpox. Chickenpox lesions are usually located on the trunk rather than the face, arms and hands. Also, patients with chickenpox experience a combination of scabs, vesicles and pustules whereas the lesions in smallpox patients are usually in the same stage of development.
Contagiousness. Chickenpox patients can transmit the virus before symptoms develop whereas smallpox patients are infectious only after signs and symptoms develop.

A physician can usually diagnose smallpox by visually examining a patient. The diagnosis may be confirmed by taking a sample of a blister or pustule and examining it under a microscope for presence of the virus.

Because the disease is highly contagious, the diagnosis of smallpox constitutes an international health emergency. Local, state and federal health officials immediately become involved with treatment.

There is no cure for smallpox. Most patients receive supportive therapy, such as intravenous (into a vein) fluids and fever and pain control. Antibiotics may be administered to prevent bacterial infections. Research is currently being conducted to determine whether antiviral medications can be used to treat smallpox. If administered within four days of infection, the smallpox vaccine can prevent or lessen the severity of the disease.

Patients with smallpox (or those suspected of having smallpox) are usually isolated from others to avoid spreading the disease.

Patients who develop smallpox may experience serious complications. About 30 percent of cases are fatal, according to the CDC. Patients who recover usually have severe scars, especially on the face, arms and legs. In some cases, smallpox may lead to blindness. Patients who recover develop immunity to the disease, so it cannot be contracted again.

Prevention methods for smallpox
Smallpox is not an active disease and does not currently require prevention methods. However, in general, the best way to prevent smallpox is to receive a vaccination. Childhood vaccination for smallpox was common in the United States until 1972. Since that time, however, a worldwide immunization program eradicated the illness.

Interest in the vaccine has resurfaced in recent years because of the potential threat that smallpox may be spread during a bioterrorist attack. Because the vaccine wears off over time, most people who were once vaccinated may still be susceptible to the disease.

The United States government has an adequate supply of the smallpox vaccine to vaccinate the country’s population if necessary. In September 2002, the U.S. Centers for Disease Control and Prevention (CDC) released a contingency plan to state health officials that details how vaccinations may be administered in the event of an emergency.

However, at this time, only certain individuals receive the vaccination, including some military personnel and healthcare professionals. The Smallpox Response Team, a select group of medical professionals, has also received the vaccine so that, in the event of an attack, they can continue to provide health care to others.

Some adverse reactions have been observed in those who have received the vaccine. They include:

Inflammation of the heart (myocarditis)
Inflammation of the membrane covering the heart (pericarditis)
A combination of myocarditis and pericarditis (myopericarditis)
Heart pain (angina) and heart attacks have occurred in a small number of those vaccinated, but it is unclear whether the vaccination caused the heart problems.

Because complications from the vaccine can be severe and sometimes fatal, health experts recommend that members of the general public do not receive the smallpox vaccination.

However, in the event of widespread vaccination during an emergency, certain individuals should not be vaccinated, including those experiencing:

Some skin conditions. Patients with eczema or a history of chronic skin conditions or who live with someone with eczema or a history of chronic skin conditions should not receive the smallpox vaccine.
Impaired immune systems. Patients with diseases that suppress the immune system, and those taking medications that suppress the immune system, should not receive the vaccine. In addition, the effect of the vaccine on people with HIV is not known. Therefore, it is recommended that these patients do not receive the vaccination.
Pregnancy. The vaccine is not known to cause birth defects, but in rare cases, it may cause fetal infection, which can lead to death of the fetus.
Allergies to ingredients in the vaccine. Ingredients include the antibiotics polymyxin B sulfate, streptomycin sulfate, chlortetracycline hydrochloride and neomycin sulfate. The vaccine does not contain penicillin.
Underlying heart disease. Patients with three or more risk factors for heart disease, including high blood pressure, diabetes, high cholesterol, smoking or a parent or sibling with heart disease, should not be vaccinated.

Many people in the United States have never received the smallpox vaccination, and others received it over 25 years ago. It is unclear how long immunity lasts after receiving the vaccination. However, it is likely that the vaccine is effective for five to 10 years. Partial immunity may last longer. People who are vaccinated a second time appear to have increased immunity.

Questions for your doctor regarding smallpox
Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about smallpox:

What is smallpox?
I thought that smallpox was eradicated decades ago. Why is it still a concern?
How does smallpox spread?
How can you distinguish smallpox from chickenpox?
Should I receive a vaccination?
Is it safe for pregnant women to get vaccinated?