Question 1

Which of the following best explains why herd immunity is effective in controlling the spread of contagious diseases, but not non-contagious diseases like tetanus?

Accepted Answer

Herd immunity relies on the interruption of person-to-person transmission, which does not occur in non-contagious diseases.

Question 2

A hospital patient develops a bloodstream infection after two months on a ventilator and urinary catheter. The pus from a bedsore is blue-green. Which organism is most likely responsible?

Accepted Answer

Pseudomonas aeruginosa

Question 3

Which biosafety level (BSL) requires the use of a full-body, air-supplied suit and is reserved for work with life-threatening, exotic agents such as Ebola virus?

Accepted Answer

BSL-4

Question 4

A laboratory is working with Streptococcus pneumoniae and hepatitis B virus. Which biosafety level is required for this work?

Accepted Answer

BSL-2

Question 5

Which of the following is the most effective single method for preventing the spread of nosocomial infections in a hospital setting?

Accepted Answer

Handwashing

Question 6

A patient is exposed to a contagious disease but is not yet showing symptoms. Which public health measure is most appropriate to prevent potential spread during the incubation period?

Accepted Answer

Quarantine

Question 7

Which of the following equations best represents the relationship between the proportion of immune individuals ($$I) in a $$population and the basic reproduction number ($$R_0) $$required to achieve herd immunity?

Accepted Answer

$$I = 1 - \frac{1}{R_0$}$$

Question 8

Which of the following is NOT a common source of nosocomial infections in hospitals?

Accepted Answer

Direct transmission from hospital food services

Question 9

Which CDC bioterrorism agent category includes diseases that are easily spread, have high mortality rates, and may cause public panic?

Accepted Answer

Category A

Question 10

A country has reduced its polio cases from being endemic to only a few isolated cases. Which public health strategy was most likely responsible for this change?

Accepted Answer

Widespread immunization leading to herd immunity

Question 11

Which of the following is a universal precaution recommended by the CDC for healthcare workers to prevent transmission of infectious agents?

Accepted Answer

Wear gloves and gowns if soiling of hands, exposed skin, or clothing with blood or body fluids is likely.

Question 12

Which of the following best describes the main difference between isolation and quarantine?

Accepted Answer

Isolation separates sick individuals from the healthy population, while quarantine separates healthy but exposed individuals during the incubation period.

Question 13

A laboratory technician is working with Mycobacterium tuberculosis. Which safety equipment is most essential for this work?

Accepted Answer

Biological safety cabinet (hood)

Question 14

Which of the following is a key reason why Pseudomonas aeruginosa is a significant cause of nosocomial infections?

Accepted Answer

It is often resistant to many antibiotics.

Question 15

Which of the following best explains why vector control is important in preventing certain infectious diseases?

Accepted Answer

It reduces the population of organisms (such as mosquitoes) that transmit diseases like malaria.

Question 16

A patient in a hospital develops pneumonia after surgery. According to the data on nosocomial infections, which site is most likely to be affected?

Accepted Answer

Pneumonia (lungs)

Question 17

Which of the following is a common misconception about herd immunity?

Accepted Answer

It is effective for all diseases, including non-contagious ones like tetanus.

Question 18

Which of the following best describes the main goal of the Biological and Toxins Weapons Convention of 1972?

Accepted Answer

To ban the development, production, stockpiling, and use of biological and toxin weapons.

Question 19

A healthcare worker is exposed to blood while treating a patient. According to CDC universal precautions, what is the most appropriate immediate action?

Accepted Answer

Wash hands and exposed skin immediately and change gloves between each patient.

Epidemiology and Control of Infectious Diseases: Herd Immunity, Transmission, and Nosocomial Infections

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