Eradication of
Small Pox
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.
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.)
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?
Created by Jennifer Yuan, Human Biology, Class of 1998
Stanford University, Stanford, CA
Last modified: February 17, 1999