smallpox virus. Smallpox was a communicable disease spread by droplets expelled
through the respiratory track. For centuries, it was one of the world's most feared
diseases and was responsible for millions of deaths. Smallpox epidemics were
disastrous. Armies sometimes suffered more deaths from smallpox than from actual
combat. Although only about 20 percent of the victims died, many others were left blind
and/or permanently scarred. A vaccine against smallpox was developed by the English
physician Edward Jenner in 1796. Since the disease only affected humans, its spread
could be controlled by worldwide immunization and quarantine procedures. Finally, in
1979, the World Health Organization announced that smallpox had been eliminated.
Since then, smallpox immunization has ceased throughout the world.
1-12. BREAKING THE RESERVOIR LINK
Isolation, quarantine, and medical surveillance are methods of controlling the
person with the disease. If the person can be separated from people who do not have
the disease, the spread of the disease is limited. This effort is even more successful
when fomites (clothing, bedding, and so forth) which have been contaminated by the
person are destroyed or cleaned in such a way that the disease organisms are killed.
a. Isolation. Isolation is a procedure whereby the infected person is separated
from other individuals. Usually, this separation is accomplished by admitting the person
to the isolation ward of a hospital. In an isolation ward, extreme care is taken to prevent
any disease organisms from escaping and infecting other people.
b. Quarantine. Quarantine is a limitation placed on the freedom to travel.
People who have been exposed to a disease may be restricted to a house or to a
limited geographic area so as to not come into contact with people who have not been
exposed to the disease. Animals coming into the United States (US) from a foreign country
are quarantined and observed for a given period of time. If the animal shows no signs
of communicable disease during the quarantine period, it is released to its owners.
c. Medical Surveillance. Quarantine may not be practicable where large
numbers of people are involved or it is simply not possible to keep the people who have
been exposed to the disease together in a single location. In such cases, individuals
who have been exposed to the disease are checked on a regular basis, usually daily. If
a person shows signs and symptoms of the disease, the appropriate measures are
taken. If, after a given time, the person has not developed signs and symptoms of the
disease, the medical surveillance is stopped.
1-13. BREAKING THE MODE OF ESCAPE LINK
Many disease-producing organisms can be controlled as they leave the reservoir
through the respiratory tract, gastrointestinal tract, or breaks in the skin.
a. Respiratory Tract. Placing a handkerchief over your mouth and nose when
you cough or sneeze helps to prevent the spread of the disease. Wearing a mask and