Operational Medicine Medical Education and Training

Principles of Epidemiology and Microbiology





One of the important landmarks in man's struggle to conquer disease was the invention of the microscope, generally attributed to Anton van Leeuwenhoek of Holland. Leeuwenhoek described the appearance of protozoa to the Royal Society of London in 1673. Thus, the world became aware of microbial life. Subsequently, Louis Pasteur, Lord Lister, Robert Koch, and others established the role of microorganisms as the causative agents of many diseases and developed techniques for determining the etiology (cause) and preventive measures for many previously uncontrolled diseases.

During the period 1893--1902, several important events occurred in military medicine that benefited not only the Army, but mankind in general. Under the direction of Army Surgeon General George Sternberg (also known as "The Father of American Bacteriology"), Walter Reed, William Gorgas, and other medical officers made dramatic progress in the etiology and control of typhoid fever, malaria, and yellow fever.

This subcourse introduces the basic principles of disease transmission and epidemiology--principles which were used by Reed and Gorgas and which are in use today. It also introduces the student to the study of the microbiological agents, which are important from a military and public health viewpoint.


Length: 122 Pages

Estimated Hours to Complete: 10

Format: PDF file

Size: 3.5 MB


Anyone may take this course. However, to receive credit hours, you must be officially enrolled and complete an examination furnished by the Nonresident Instruction Branch at Fort Sam Houston, Texas. Enrollment is normally limited to Department of Defense personnel. Others may apply for enrollment, but acceptance is not guaranteed.


Principles of Epidemiology and Microbiology

Distance Learning Course
122 Pages
Est. 10 Hours
3.5 MB pdf file

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Section I. Introduction

Section II. Bacteria

Section III. Virsus

Section IV. Fungi

Section V. Protozoa

Section VI. Helminths



Section I. Microbiology of Water and Sewage

Section II. Disinfection and Sterilization

Section III. Packaing Micarobiological Specimens For Shipment







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.


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.


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.


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


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