Define symbiosis. Differentiate commensalism, mutualism, and parasitism, and give an example of each.
Ch. 14 - Principles of Disease and Epidemiology

Tortora14th EditionMicrobiology: An IntroductionISBN: 9780138200398Not the one you use?Change textbook
Chapter 14, Problem 1
Differentiate the terms in each of the following pairs:
a. Etiology and pathogenesis
b. Infection and disease
c. Communicable disease and noncommunicable disease
Verified step by step guidance1
Step 1: Define 'etiology' as the study of the cause or origin of a disease, focusing on identifying the specific agent or factors responsible for the disease. Define 'pathogenesis' as the process by which the disease develops and progresses in the host, including the mechanisms of tissue damage and clinical manifestations.
Step 2: Define 'infection' as the invasion and multiplication of microorganisms such as bacteria, viruses, or parasites within the host's body. Define 'disease' as the condition that results when the infection causes damage or dysfunction in the host, leading to symptoms and signs.
Step 3: Define 'communicable disease' as an illness that can be transmitted from one person to another, either directly or indirectly, through various modes such as contact, droplets, or vectors. Define 'noncommunicable disease' as a disease that is not transmitted between people, often caused by genetic, environmental, or lifestyle factors.
Step 4: For each pair, highlight the key difference: etiology focuses on cause, pathogenesis on development; infection is presence of microbes, disease is the harmful effect; communicable diseases spread between hosts, noncommunicable do not.
Step 5: Summarize by providing examples for each term to reinforce understanding, such as tuberculosis for communicable disease and diabetes for noncommunicable disease.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Etiology and Pathogenesis
Etiology refers to the study of the cause or origin of a disease, identifying the specific agent or factors responsible. Pathogenesis describes the mechanism by which the disease develops and progresses in the host, including the biological and physiological changes that occur.
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Infection and Disease
Infection is the invasion and multiplication of microorganisms such as bacteria, viruses, or fungi within the body. Disease occurs when the infection causes damage or dysfunction in the host, leading to symptoms and clinical signs.
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Chronic & Latent Infection Disease Progression
Communicable Disease and Noncommunicable Disease
Communicable diseases are illnesses that can be transmitted from one person to another, directly or indirectly, often caused by infectious agents. Noncommunicable diseases are not spread between people and usually result from genetic, lifestyle, or environmental factors.
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Communicable vs. Noncommunicable Diseases
Related Practice
Textbook Question
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Textbook Question
All members of a group of ornithologists studying barn owls in the wild have had
salmonellosis (Salmonella gastroenteritis). One birder is experiencing her third infection. What is the most likely source of their infections?
a. The ornithologists are eating the same food.
b. They are contaminating their hands while handling the owls and nests.
c. One of the workers is a Salmonella carrier.
d. Their drinking water is contaminated.
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Textbook Question
The emergence of new infectious diseases is probably due to all of the following except:
a. The need of bacteria to cause disease
b. The ability of humans to travel by air
c. Changing environments (e.g., flood, drought, pollution)
d. A pathogen crossing the species barrier
e. The increasing human population
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