Smallpox: Symptoms, Causes, Treatments & Preventions


Smallpox is a disease caused by the Variola major virus. Some experts say that over the centuries it has killed more people than all other infectious diseases combined. Worldwide immunization stopped the spread of smallpox three decades ago. The last case was reported in 1977. Two research labs still keep small amounts of the virus. Experts fear bioterrorists could use the virus to spread disease.

Smallpox spreads very easily from person to person. Symptoms are flu-like. They include

  • High fever
  • Fatigue
  • Headache
  • Backache
  • A rash with flat red sores

There is no treatment. Fluids and medicines for pain or fever can help control symptoms. Most people recover, but some can die. Those who do recover may have severe scars.

The U.S. stopped routine smallpox vaccinations in 1972. Military and other high-risk groups continue to get the vaccine. The U.S. has increased its supply of the vaccine in recent years. The vaccine makes some people sick, so doctors save it for those at highest risk of disease.

Symptoms of Smallpox

The first symptoms of smallpox usually appear 12 to 14 days after you’re infected. During the incubation period of seven to 17 days, you look and feel healthy and can’t infect others.

Following the incubation period, a sudden onset of flu-like signs and symptoms occurs. These include:

A few days later, flat, red spots appear first on your face, hands and forearms, and later on your trunk. Within a day or two, many of these lesions turn into small blisters filled with clear fluid, which then turns into pus. Scabs begin to form eight to nine days later and eventually fall off, leaving deep, pitted scars.

Lesions also develop in the mucous membranes of your nose and mouth and quickly turn into sores that break open.

Causes of Smallpox

Smallpox is caused by a poxvirus called variola (Poxviridiae family of viruses). Variola is a relatively large virus that contains double-stranded DNA. The virus can be found in large numbers in many organs (skin, kidneys, spleen, liver, and other organs). Death occurs because of overwhelming toxemia, thought to be due to immune complexes trying to react to the large number of viral particles. Variola infection only occurs in humans, which was helpful in eradicating the disease. There are two strains called respectively variola major and variola minor (also known as alastrim). As implied by the names, variola major is more likely to cause serious disease and death than variola minor.

How is Smallpox spread?

Smallpox is contagious. That means the virus can spread to others. It spreads through tiny drops of an infected person’s saliva (spit) when the person coughs, talks, or sneezes. Smallpox usually passes from person to person during close, face-to-face contact.

How is it diagnosed?

If someone does get smallpox, a doctor can recognize the disease because it causes a special kind of rash. The rash shows up as blisters on the skin that fill with fluid and crust over. This might sound like chickenpox, but the blisters look different from the blisters that chickenpox causes. The other symptoms of smallpox are like those of many other less serious illnesses: fever, headache, backache, and feeling tired.

Smallpox Treatments

No cure for smallpox exists. In the event of an infection, treatment would focus on relieving symptoms and keeping the person from becoming dehydrated. Antibiotics might be prescribed if the person also develops a bacterial infection in the lungs or on the skin.

Preventions of Smallpox

In the event of an outbreak, people who had smallpox would be kept in isolation in an effort to control the spread of the virus. Anyone who had contact with someone who developed an infection would need the smallpox vaccine, which can prevent or lessen the severity of the disease if given within four days of exposure to the smallpox virus.

The vaccine uses a live virus that’s related to smallpox, and it can occasionally cause serious complications, such as infections affecting the heart or brain. That’s why a general vaccination program for everyone isn’t recommended at this time. The potential risks of the vaccine outweigh the benefits, in the absence of an actual smallpox outbreak.