The Small Pox Story

Before small pox was eradicated in 1977, it was one of the most infectious and deadly diseases in the world, afflicting millions of people each year regardless of age, race, or socioeconomic status. To better understand the impact of this disease on the world from centuries ago, to the discovery of its vaccine, to its eventual eradication, take a look at these quotes, compiled by Dr. Siegel. For some close-up photographs and a detailed description of the disease's progression, click here.

There are two forms of small pox: variola major and variola minor. Variola major has a case fatality rate of approximately 25%, while variola minor, a less virulent form, has a case fatality rate below 1%. Although the two forms cause disease of different severity, they are indistinguishable from one another.


| Introduction | Small Pox | Classification and Taxonomy | Other Human Viruses and Diseases | Transmission |
| Immune Response and Host Defenses | Vaccination | Eradication of Small Pox and Other Viral Diseases| Useful Web Links | References |

+ The Small Pox Vaccine

The vaccine for small pox was the first vaccine ever developed. In fact, the term "vaccine" comes from the Latin word for cow, vaccinus, since the original small pox vaccine was made using the cow pox virus.

Prior to the development of the small pox vaccine, at least two other forms of inoculation were used to try to protect people against the deadly disease. For centuries in China, the virus was inoculated into the nose, while in the Middle East there was the practice of variolation, in which the virus was inoculated into the skin.

In 1721, Lady Mary Wortley Montagu, the wife of the British ambassador to Turkey, learned about variolation in Turkey and had her children variolated, thus introducing the practice to England. Variolation was then adopted by Princess Caroline two years later, which resulted in its widespread acceptance.

In 1796, the world's first vaccination was performed when an English country doctor named Edward Jenner inoculated James Phipps, an eight year old boy, with cow pox virus. Jenner had observed that, although small pox was a widespread disease, milkmaids never seemed to get the disease. This was because they had been infected by cow pox from the cows they worked with, and this virus was similar enough to small pox to protect against it. A month and a half after inoculating Phipps, Jenner tested the effectiveness of his vaccine by injecting the boy with live small pox virus. Phipps was completely protected and did not show any symptoms. In 1798, Jenner published an article called "An Inquiry into the Causes and Effects of the Variolae Vaccinae," reporting the efficacy of his new treatment.

Although Jenner's accomplishment was a landmark event in the history of medicine, the vaccine that was eventually used to eradicate small pox was made from vaccinia, not cow pox. The vaccinia virus, used as a live vaccine against small pox, is a relatively avirulent virus that is similar to cow pox, but its origins are not clearly understood. Inoculation with vaccinia causes a single pock at the site of injection, which dries up and scabs after about ten days, leaving a vaccination scar. By this time, the vaccinated individual has become immune to both vaccinia and small pox.

Possible complications of vaccinia injection include eczema vaccinatum and postvaccinal encephalitis. Although the probability of either of these occuring is extremely small, the risk of having these side effects was declared to be greater than the risk of contracting small pox in the United States by 1971.

Once the disease had been eradicated, most remaining laboratory stocks of the virus were destroyed. Since 1983, there have only been two known repositories left in the world: at the CDC in Atlanta, and at the Moscow Research Institute for Viral Preparations.

(See Eradication of Small Pox for further discussion of the advantages of the vaccine which made eradication possible.)


| Introduction | Small Pox | Classification and Taxonomy | Other Human Viruses and Diseases | Transmission |
| Immune Response and Host Defenses | Vaccination | Eradication of Small Pox and Other Viral Diseases| Useful Web Links | References |

+ Eradication of Small Pox

By the 1900s, vaccination had reduced small pox to a minor threat in the United States and most of Europe. The last case of small pox in the U.S. occured in Texas in 1949. In 1958, the Russian delegate to the World Health Assembly made a formal proposal to eradicate small pox. The resolution was passed a year later, and one by one, countries around the world succeeded in eliminating the disease. With surveillance and containment, the deadly disease was eventually eradicated. The last case of small pox was reported in Bangladesh in 1975, and the last case of variola minor occured in Somalia in 1977. The WHO waited for two more years, then declared on October 26, 1977 that small pox had become the first disease ever to be eradicated.

What characteristics of small pox made its eradication possible?

Can other viral diseases be eradicated as well? Currently, the two main candidates for eradication are measles and poliomyelitis. Both viruses, like small pox, lack an animal reservoir and have high morbidity and mortality rates. Effective vaccines have been developed for both diseases, although polio may require multiple doses. Surveillance and containment, however, may be impossible because individuals infected by either virus can spread infection to others before symptoms appear.


| Introduction | Small Pox | Classification and Taxonomy | Other Human Viruses and Diseases | Transmission |
| Immune Response and Host Defenses | Vaccination | Eradication of Small Pox and Other Viral Diseases| Useful Web Links | References |

Created by Jennifer Yuan, Human Biology, Class of 1998
Stanford University, Stanford, CA
Last modified: February 17, 1999