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Ch. 9 - Principles of Infectious Disease and Epidemiology
Norman-McKay- Microbiology: Basic and Clinical Principles 2nd Edition
Norman-McKay2nd EditionMicrobiology: Basic and Clinical PrinciplesISBN: 9780137661619Not the one you use?Change textbook
All textbooksNorman-McKay 2nd EditionCh. 9 - Principles of Infectious Disease and EpidemiologyProblem 10
Chapter 9, Problem 10

Label the following modes of transmission as either direct or indirect. For all indirect transmissions, also specify which of the three categories of indirect transmission is involved.


Transmission of HIV across the placenta:
Transmission of a pathogen through drinking contaminated water:
Transmission of malaria by a mosquito to a human host:
Transmission of a pathogen through breast milk:
Transmission of rabies by a dog bite:
Transmission of a pathogen by touching a doorknob:
Transmission of a pathogen by a contaminated needle:
Transmission of a respiratory pathogen through respiratory droplets:

Verified step by step guidance
1
Step 1: Understand the difference between direct and indirect transmission. Direct transmission involves immediate transfer of pathogens from an infected host to a susceptible host without an intermediate object or organism. Indirect transmission involves an intermediate vehicle, vector, or fomite.
Step 2: For each mode of transmission, determine if the pathogen moves directly from one host to another (direct) or if it involves an intermediate step (indirect).
Step 3: For indirect transmissions, classify the type of indirect transmission into one of three categories: vehicle-borne (contaminated objects or substances like water, food, or needles), vector-borne (transmission via living organisms like mosquitoes or ticks), or fomite-borne (inanimate objects like doorknobs).
Step 4: Apply these definitions to each example: - HIV across the placenta involves direct transmission from mother to fetus. - Drinking contaminated water involves indirect transmission via a vehicle (water). - Malaria transmitted by a mosquito is indirect transmission via a vector. - Breast milk transmission of a pathogen is direct transmission from mother to infant. - Rabies by a dog bite is direct transmission through contact with saliva. - Touching a doorknob involves indirect transmission via a fomite. - A contaminated needle is indirect transmission via a vehicle (needle). - Respiratory droplets are direct transmission through close contact.
Step 5: Summarize your answers by labeling each transmission as direct or indirect, and for indirect, specify the category (vehicle, vector, or fomite) based on the reasoning above.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Modes of Transmission in Infectious Diseases

Modes of transmission describe how pathogens spread from one host to another. They are broadly classified into direct transmission, involving immediate transfer through physical contact or bodily fluids, and indirect transmission, where pathogens are transferred via intermediaries like objects, vectors, or the environment.
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Direct vs. Indirect Transmission

Direct transmission occurs through direct physical contact, such as touching, biting, or bodily fluid exchange. Indirect transmission involves an intermediate vehicle or vector, including fomites (contaminated objects), vehicles (water, food), or biological vectors (insects), which carry pathogens to new hosts without direct contact.
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Categories of Indirect Transmission

Indirect transmission is divided into three categories: vehicle-borne (pathogens spread via contaminated food, water, or objects), vector-borne (transmission through living organisms like mosquitoes), and airborne (pathogens carried by dust or droplets suspended in air). Identifying the category helps in understanding and controlling disease spread.
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Related Practice
Textbook Question

Diseases that the CDC collects information on through collaboration with state and local health authorities are called (NCLEX/HESI/TEAS)

a. Communicable diseases.

b. Reportable diseases.

c. Nationally notifiable diseases.

d. Investigative diseases.

e. Case report illnesses.

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Textbook Question

A(n) _______________________ groups the study populations by exposure versus nonexposure to a certain risk factor to see if either group develops the outcome in question.

a. Experimental study

b. Case report

c. Cross-sectional study

d. Correlation study

e. Observational study

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Textbook Question

An epidemiological study design that is commonly used for determining the efficacy of a drug therapy is a(n)

a. Experimental study.

b. Case report.

c. Cross-sectional study.

d. Correlation study.

e. Observational study.

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Textbook Question

From the following choices, select all of the factors that impact prevalence rate.

a. Duration of a disease

b. The type of pathogen responsible (such as if the pathogen is viral or bacterial)

c. Cure rates for a disease

d. The pathogenicity of the microbe that causes the disease

e. The effectiveness of preventive measures

f. The incidence rate of a disease

g. The quality of diagnostic tools

h. The severity of the disease

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