The story of smallpox is one of modern medicine’s most successful public health campaigns. It is one of the only infectious diseases completely eradicated due to worldwide vaccination programs. There has not been a naturally occurring documented case since October 26, 1977 and the global eradication of smallpox was officially announced in 1979.
In 1980, the World Health Organization recommended that all countries stop their vaccination program.
The history of the smallpox virus is interesting. The Variola virus causing smallpox is in the orthopox virus family, which also includes cowpox and monkeypox. It plagued Europe and Asia for centuries, and when European explorers ventured to the New World, it nearly decimated the Native American population. In 1796 an English scientist Edward Jenner, who is credited as the pioneer of the smallpox vaccine, discovered that milkmaids who had been exposed to the cowpox virus, if or when they were infected with the smallpox virus, contracted a much milder form of the disease.
Jenner then postulated that cowpox infection gave some immunity to smallpox. He tested his theory by inoculating a young boy, James Phipps with a milder cowpox virus collected from the cowpox pustules of a milkmaid. Then, he exposed the boy to smallpox infected material called variolation; this type of experimentation aimed to prove immunity, however it often resulted in contracting the disease and sometimes death. In this case, Phipps did not get sick from the exposure.
This vaccination was eventually accepted as safer way to confer immunity; yet in 1840 variolation, the use of smallpox itself to confer immunity, was banned. The word vaccine finds its root in the Latin word for cow, vacca.
The Variola virus only infects humans and is spread by human-to-human contact, and is especially damaging to children and pregnant women. Smallpox disease has a high mortality rate, killing about 1/3 or 30% of people infected with the Variola virus. The virus is inhaled; once in the lungs, it multiplies and spreads via the bloodstream to the skin, intestines, kidneys and brain. Symptoms including fever chills, nausea, vomiting, headache and backache begin about 1 week after exposure.
In the skin it creates a rash that forms a blister and pus filled, pimple-like sores called pustules. The rash appears about 2 weeks after infection, and at this point, the patient is highly contagious. The rash looks similar to the chickenpox rash, but chickenpox rash can occur in different stages of development –new blisters can appear while others have pustules and still others are healing and scabbing.
Conversely, the smallpox rash is always in a uniform stage. First, blisters appear before maturing to postules. Those that do survive will have horribly deep scarring of the skin. The virus also causes lesions that start in the mouth and then spread to the face, arms, legs and torso.
Chickenpox progresses from the arms and legs to the torso and is rarely seen on the palms, soles of the feet, armpits or elbows.