Q: Calculate the infection fatality ratio (IFR) if 1000 people are infected with a disease and 25 die from it. Use the formula $$\text{IFR} = \frac{\text{Number of deaths}}{\text{Total number of infected individuals}} \times 100\%.$$

$$\text{IFR} = \frac{25}{1000} \times 100\% = 2.5\%$$

Question 1

Which of the following best describes the difference between infection and disease?

Accepted Answer

Infection is the invasion or colonization of the body by pathogens, while disease is an abnormal state in which the body is not performing normal functions due to a microbe or its products.

Question 2

Which of the following is an example of an overt pathogen?

Accepted Answer

Staphylococcus aureus causing skin infections in healthy individuals.

Question 3

Which body site is normally sterile under healthy conditions?

Accepted Answer

Cerebrospinal fluid (CSF)

Question 4

A newborn delivered by cesarean section is most likely to have a microbiome resembling which of the following?

Accepted Answer

Human skin, with Staphylococcus aureus as a prevalent microbe

Question 5

Which of the following best illustrates mutualism in the human microbiome?

Accepted Answer

E. coli in the large intestine synthesizing vitamin K for the host while receiving nutrients

Question 6

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

Accepted Answer

The pathogen must be present in the environment before disease occurs.

Question 7

A disease that is constantly present in a population is best described as:

Accepted Answer

Endemic

Question 8

Calculate the infection fatality ratio (IFR) if 1000 people are infected with a disease and 25 die from it. Use the formula $$	ext{IFR} = \frac{	ext{Number of deaths}}{	ext{Total number of infected individuals}} 	imes 100\%.$$

Accepted Answer

$$	ext{IFR} = \frac{25}{1000} 	imes 100\% = 2.5\%$$

Question 9

Which of the following is an example of a zoonosis?

Accepted Answer

Rabies transmitted from a dog to a human via a bite

Question 10

Which type of transmission involves pathogens carried by a nonliving object such as a contaminated doorknob?

Accepted Answer

Indirect contact transmission via a fomite

Question 11

A patient develops a secondary infection after being treated for pneumonia. Which best describes this scenario?

Accepted Answer

An opportunistic infection following a primary infection

Question 12

Which of the following is a predisposing factor that can increase susceptibility to infectious disease?

Accepted Answer

Compromised host due to immunosuppressive therapy

Question 13

During which stage of disease is a patient most likely to experience the most severe signs and symptoms?

Accepted Answer

Period of illness

Question 14

Which of the following is a mechanical vector transmission?

Accepted Answer

A fly landing on food and transferring pathogens from its feet

Question 15

Which of the following practices is part of standard precautions in healthcare settings?

Accepted Answer

Hand hygiene before and after patient contact

Question 16

Which of the following is a contributing factor to emerging infectious diseases?

Accepted Answer

Genetic recombination between organisms, such as Escherichia coli O157:H7

Question 17

Which type of epidemiology involves the collection and analysis of data to identify patterns and sources of disease?

Accepted Answer

Descriptive epidemiology

Question 18

If the reproductive number $$R_0$$ for a disease is 3, what does this mean?

Accepted Answer

On average, one infected individual will transmit the disease to three other people.

Question 19

Which of the following is NOT a method to control healthcare-associated infections (HAIs)?

Accepted Answer

Avoiding handwashing between patients

Question 20

A disease with a high case fatality ratio (CFR) but a low infection fatality ratio (IFR) most likely indicates:

Accepted Answer

Many diagnosed cases result in death, but the overall number of infected individuals (including undiagnosed cases) is much higher.

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