TABLE OF CONTENTS
INTRODUCTION
1. INTRODUCTION DISEASE TRANSMISSION AND
EPIDEMIOLOGY
Exercises
2. PUBLIC HEALTH MIVROBIOLOGY
Section I. Introduction
Section II. Bacteria
Section III. Virsus
Section IV. Fungi
Section V. Protozoa
Section VI. Helminths
Exercises
3. PRACTICAL APPLICATION OF MICROBIOLOGY
Section I. Microbiology of Water and Sewage
Section II. Disinfection and Sterilization
Section III. Packaing Micarobiological Specimens For
Shipment
Exercises
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LESSON 1
INTRODUCTION TO DISEASE TRANSMISSION AND
EPIDEMIOLOGY
1-1. GENERAL
Disease and non-combat injury have plagued military
commanders since time immemorial. In every war or combat action in
which the United States (US) has ever participated, disease and
non-combat injury have contributed far more to the ineffectiveness of
troops than have losses due to enemy action. A commonly held
misconception is that since the advent of antibiotics and advanced
medical techniques, disease and accident are no longer matters of
major concern. Nothing could be farther from the truth. Statistics
show that during the heaviest periods of combat action since the
outbreak of World War II, hospital admissions caused by disease and
non-combat injury have exceeded those caused by battle injury by a
ratio of from 3:1 to 19:1.
Prior to World War II, these ratios were even less favorable. Much
credit for the improvement in the situation must be given to
epidemiologists who discovered the causes of many of the diseases that
had ravaged troops for centuries. As more is learned in the future,
the number of needless deaths and illnesses will hopefully be further
reduced. The key to opening the door to further discovery of methods
of disease control is a thorough knowledge of the various agents of
disease and the nature of disease transmission.
1-2. RESPONSIBILITIES FOR HEALTH
The commander of a military organization is
responsible for the health of his
command.
In the fulfillment of this
responsibility, he is assisted by a staff of trained
specialists. The
surgeon, who is the chief medical
advisor to the commander, provides
technical medical
advice and is responsible for the
successful functioning of the medical
service within the
command. Additional support is readily
available from field medical
treatment facilities, Army
medical laboratories, Medical
Department table of
organization and equipment
(TOE) units, and
facilities of The Surgeon General's
office. Emphasis
throughout the Army at all levels is
on prevention of disease, using all
available information
concerning the epidemiology of
those diseases which are of military or public health significance.
1-3. DEFINITIONS
In order to approach the subject of disease
transmission and epidemiology in a clear and logical manner, it is
necessary to establish a common ground in the use of terminology. The
following terms will be used frequently throughout this subcourse.
a. Disease.
Disease is an impairment of the normal state of the living animal or
plant body that affects the performance of the vital functions. The
presence of disease usually results in visible signs or symptoms.
b. Communicable Disease.
A communicable disease is an illness that can be transmitted person to
person or from animal to person.
c. Agent.
An agent is a disease-producing organism or substance.
d. Infection.
Infection is the entrance and multiplication of infectious
(disease-producing) agents into the body of man or animal.
e. Reservoir.
A reservoir is the source of a disease, harboring the infectious
agent(s). The agent either multiplies or undergoes some development
with the organism or substance acting as the reservoir.
f. Mode of Transmission.
The mode of transmission is the means by which a disease is
transmitted from one person or animal to another.
g. Vector.
A vector is an animal or arthropod that plays a part in the
transmission of disease. A disease vector may be either the reservoir
or the vehicle in disease transmission.
h. Host.
The host is the living body upon which a parasite or infectious agent
lives--the final recipient of a disease agent. The host of a disease
may be either a case or a carrier.
i. Case.
A case refers to a person who is actually ill with a disease.
j. Carrier. A carrier
is an individual (or animal) who is infected with a disease, agent and
is capable of transmitting the disease, but who usually does not
exhibit clinical symptoms.
k. Incubation
Period. The incubation period is the time interval between
the entrance of an infectious agent into a host and the appearance of
symptoms.
l. Spectrum of
Infection. The spectrum of infection is the broad gradation
of disease infection from no apparent symptoms (such as the carrier
state) through severe illness and death.
m. Endemic.
Endemic refers to the usual level of occurrence of a disease within a
given geographical area.
n. Epidemic.
Epidemic is the occurrence of a disease clearly in excess of the
normal expectancy within a given geographical area.
o. Pandemic.
Pandemic is the occurrence of disease over a wide geographical area
and affecting an exceptionally high percentage of the population.
p.
Epidemiology. Epidemiology is the study of the determinants
and distribution of disease and injury in a given population.
q. Vehicle.
A vehicle is an inanimate object that facilitates the transmission of
a disease-causing agent.
1-4. COMMUNICABLE DISEASES
Although not all diseases of military importance are
communicable, this lesson will focus upon the communicable
diseases-those that can be transmitted from person to person or from
an animal to a person. These diseases may be classified into five
groups, based upon the manner in which they are spread, the area of
the body that they affect, and the type of control needed to prevent
their spread.
a. Intestinal
Diseases. These diseases are usually transmitted by food or
water that has become contaminated with feces from an infected human
or animal. Examples are typhoid and paratyphoid fevers, dysentery, and
cholera.
b. Respiratory
Diseases. These diseases are usually transmitted from
person to person by discharges from the nose, mouth, throat, or lungs
of an infected person. Examples are the common cold, influenza,
pneumonia, streptococcal sore throat, and tuberculosis.
c. Sexually
Transmitted Diseases. These diseases are transmitted from
person to person by sexual intercourse. Examples are syphilis,
gonorrhea, herpes, hepatitis B, and chancroid.
d.
Arthropod-Borne Diseases. These diseases are transmitted
from person to person or from animal to person by insects or other
arthropods. Examples are malaria, typhus, and yellow fever.
e. Miscellaneous Diseases.
This group includes those communicable diseases that do not fall into
any of the above groups. Examples are rabies (hydrophobia), tetanus
(lockjaw), and dermatophytosis (athlete's foot).
From
Principles of Epidemiology and Microbiology
