Q: Calculate the incidence proportion of a disease if 18 new cases occur in a population of 110 susceptible individuals during a month. Express your answer as a percentage using the formula $$Incidence = \frac{\text{New cases}}{\text{Population at risk}} \times 100\%.$$

$$Incidence = \frac{18}{110} \times 100\% = 16.4\%$$

Question 1

Which of the following best describes a mutualistic relationship between two organisms?

Accepted Answer

Both organisms benefit from the relationship.

Question 2

A newborn baby acquires its microbiota through which of the following methods?

Accepted Answer

All of the above.

Question 3

Which of the following is NOT a way in which the human microbiome protects against pathogens?

Accepted Answer

Microbes of our microbiome create compounds that help us digest our food.

Question 4

Which of the following is a sign, rather than a symptom, of infectious disease?

Accepted Answer

Fever of 39°C (102°F)

Question 5

A disease that is consistently present in a population with a regular pattern is called:

Accepted Answer

Endemic

Question 6

Calculate the incidence proportion of a disease if 18 new cases occur in a population of 110 susceptible individuals during a month. Express your answer as a percentage using the formula $$Incidence = \frac{	ext{New cases}}{	ext{Population at risk}} 	imes 100\%.$$

Accepted Answer

$$Incidence = \frac{18}{110} 	imes 100\% = 16.4\%$$

Question 7

Which of the following is a limitation of Koch’s postulates?

Accepted Answer

Some pathogens cannot be grown in pure culture.

Question 8

Which of the following is the best example of analytical epidemiology?

Accepted Answer

Comparing the rate of lung cancer between smokers and non-smokers.

Question 9

Which of the following statements about herd immunity is true?

Accepted Answer

Herd immunity is when enough people are vaccinated against a disease so that it cannot easily spread.

Question 10

Which of the following is NOT a factor contributing to hospital-acquired infections (HAIs)?

Accepted Answer

Some patients are allergic to certain medications.

Question 11

A tick infected with Borrelia burgdorferi bites a human and transfers the bacteria. The wound the tick makes is the pathogen’s:

Accepted Answer

Portal of entry

Question 12

Which of the following is an example of a mechanical vector?

Accepted Answer

A fly lands on raw chicken, then on a cooked plate of food, transferring Salmonella bacteria.

Question 13

Which of the following statements about airborne transmission is true?

Accepted Answer

Droplet nuclei can remain airborne for hours, allowing indirect transmission to occur.

Question 14

Which of the following is NOT an example of a zoonotic disease?

Accepted Answer

Measles virus; humans.

Question 15

Which of the following is the major difference between vertical and horizontal disease transmission?

Accepted Answer

Vertical transmission only occurs between mother & baby. Horizontal transmission is any other mode of transmission.

Question 16

Which of the following is a virulence factor?

Accepted Answer

A capsule that protects bacteria from phagocytosis.

Question 17

Which of the following is the most effective way to prevent the spread of disease via direct contact?

Accepted Answer

Hand washing

Question 18

Which of the following best describes the function of TReg cells in immune tolerance?

Accepted Answer

They suppress the activity of other T cells to prevent them from targeting the host microbiome and self-cells.

Question 19

Which of the following is NOT a limitation of Koch’s postulates?

Accepted Answer

All pathogens can be grown in pure culture.

Principles of Disease and Epidemiology: Mini-Textbook Study Guide

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