MODE OF ENTRY
The mode of entry refers to the avenue by which the disease organism enters the
body of the healthy person (host). It is closely associated with the mode of escape and
the mode of transfer. Disease organisms that escape on droplets when a person
sneezes, for example, enter the body of the healthy person when the person inhales air
containing some of these droplets. Malaria organisms escape when the mosquito
punctures the infected person's skin, travels in the mosquito's digestive system, and
enters the healthy person when the mosquito punctures that person's skin.
The susceptible host is the person who does not have the disease but who can
"catch" the disease if exposed to the disease organism. This person then becomes a
reservoir and, in turn, provides the means by which new hosts can be infected.
Section II. BREAKING THE CYCLE OF INFECTION
1-10. BREAKING THE CHAIN
Paragraph 1-3 compared the cycle of infection to a chain with six links. Like a
chain, the cycle of infection can be broken if any one of the six links are broken. In the
following paragraphs, we will discuss how the spread of communicable diseases can be
controlled by attacking these links.
1-11. BREAKING THE CAUSATIVE AGENT LINK
a. Antibiotics. One way of breaking the chain is by destroying the disease
organisms (causative agent) that are in the body. This is done through the use of
antibiotics. Antibiotics are drugs produced from fungi and bacteria. They attack certain
disease-producing organisms, but do not attack the person's body. The death rates
from many diseases (such as pneumonia, meningitis, scarlet fever, and syphilis) have
been drastically reduced through the use of antibiotics such as penicillin, streptomycin,
(1) Penicillin. Penicillin is an antibiotic produced from a mold of the genus
Penicillium and was the first antibiotic. It was discovered by the British bacteriologist
Alexander Fleming in 1929, but was extremely hard to produce. The first successfully
medical use of penicillin occurred in 1941. In 1943, a breakthrough allowed penicillin to
be produced in large amounts.
(2) Streptomycin. In 1944, an American bacteriologist isolated the antibiotic
streptomycin from another type of fungus. Since then, several other antibiotics have
been discovered and used in treating diseases.
b. Extinction. If the organism that causes the disease can be eliminated, then
the disease itself will be eliminated. This process has been successfully used with the