Question 1

Human population growth and expansion contribute to emergence of diseases.

Accepted Answer

As human populations continue to grow and expand into previously undeveloped areas, they often come into contact with new pathogens and diseases. Additionally, increased human travel and trade can facilitate the spread of infectious diseases beyond their original locations. Climate change and environmental degradation can also contribute to the emergence of new diseases.

Question 2

Why is it important to include a placebo in a scientific study to assess the effectiveness of a drug?

Accepted Answer

Including a placebo-treated group is important because it allows researchers to determine whether the changes observed in the drug-treated illness group are due to a psychological effect (placebo effect) or a physiologic/pharmacologic effect of the drug. This helps to ensure that any observed treatment effects are actually due to the drug itself and not just the patient's belief in the efficacy of the treatment.

Question 3

In this case, the reservoir of infection was likely the

Accepted Answer

Chicken wings are a common source of foodborne infections, making them the likely reservoir in this scenario.

Question 4

All of the following is/are reservoirs of infection in a hospital setting EXCEPT

Accepted Answer

Sterile surgical equipment should not be a reservoir of infection in a hospital setting as it is expected to be free of all microorganisms. In contrast, the other options listed can all potentially be reservoirs of infection in a hospital setting.

Question 5

Select the sequence that indicates the steps that occur in the chain of infection.
1) Transmission.
2) Susceptible host.
3) Reservoir of infectious agent.
4) Portal of exit.
5) Portal of entry.

Accepted Answer

The correct sequence for the chain of infection starts with the reservoir of the infectious agent (where the pathogen lives and multiplies), followed by the portal of exit (the path by which the pathogen leaves the reservoir), transmission (how the pathogen is spread to another host), portal of entry (how the pathogen enters a new host), and finally, the susceptible host (an individual who can become ill from the pathogen).

Question 6

A picnic was attended by 1,000 people. Potato salad was served at the event. The next day, 140 people reported vomiting and diarrhea. What was the attack rate of this food-borne illness?

Accepted Answer

The attack rate is calculated by dividing the number of people who got sick by the total number of people who attended the event, then multiplying by 100. 
Attack rate = (140/1,000) x 100 = 14%. 
Therefore, the answer is B.

Question 7

Which of the statements about transmission of pathogens is True?

Accepted Answer

Droplet transmission is a particularly important source of contamination in densely populated buildings such as schools, where people are in close proximity to each other and the droplets can spread easily through coughing, sneezing, or talking.

Option A is incorrect as vertical transmission refers to transmission of a pathogen from a mother to her child (during pregnancy, birth, or breastfeeding).
Option B is incorrect as it refers to the spread of a pathogen from a mother to her offspring, and not specifically from mother to fetus.
Option C is incorrect as sexual intercourse is a form of direct contact.
Option E is incorrect as droplet nuclei are small droplets of pathogen-containing fluid that can remain suspended in the air and travel further than a meter.

Question 8

A fly that walks on feces and picks up E. coli O157:H7 then lands on food and transfers the microorganisms, is considered a

Accepted Answer

A mechanical vector is an organism, such as a fly or cockroach, that can physically transfer microorganisms from one location to another, such as from feces to food. Biological vectors, on the other hand, are insects or other organisms that themselves transmit a pathogen, such as a mosquito transmitting malaria. Fomites are objects that can transfer pathogens, such as a doorknob. Cross-contamination refers to the transfer of pathogens from one food to another, or from one surface to another. A fly transferring E. coli O157:H7 fits the definition of a mechanical vector, as it is transferring the microorganisms without being infected with them itself. Therefore, the best choice is A) mechanical vector.

Question 9

In 1918-1919, an influenza virus infected about 500 million people worldwide, killing at least 50 million of them. This disease is best described as a(n) ________.

Accepted Answer

The scale of the influenza virus outbreak in 1918-1919, which affected millions of people worldwide, indicates that it was a pandemic. An epidemic refers to the widespread occurrence of a disease within a community, whereas an outbreak refers to a sudden increase in the number of cases above a typical amount. Sporadic outbreaks refer to occasional cases of a disease, and an endemic disease is continually present in a certain area or population.

Question 10

Explain the most likely reason why smallpox was successfully eradicated but rabies probably never will be.

Accepted Answer

Smallpox was only found in humans; rabies is found in numerous animal reservoirs. We cannot reasonably eliminate rabies in all of the animal reservoirs that exist.

Question 11

Please select the False statement.

Accepted Answer

Herd immunity can be overcome by a pathogen if the pathogen mutates or if the immunity level in the population decreases.

Question 12

The situation described in this case study is an example of a(n)

Accepted Answer

The situation described in the case study is an example of a common-source epidemic because several students became ill in the same time frame after consuming food from the same source.

Question 13

Explain how the incubation period can influence the spread of an infectious agent.

Accepted Answer

Depending on the infectious agent and the illness, an asymptomatic carrier in the incubation period might be shedding infectious microbes to his/her surroundings. In such a case, a longer incubation period would lead to a greater spread of the disease as the carrier comes into contact with more individuals while he/she is generally appearing to be healthy.

Question 14

Some populations more than others are likely to be affected by a given pathogen. Many population characteristics influence the occurrence of disease. Which of the following MOST likely explains why some students at the picnic did not get ill?

Accepted Answer

Behavioral practices, such as dietary choices, can significantly influence exposure to pathogens. In this scenario, vegetarians and vegans likely avoided the contaminated food, which was presumably meat, thus they did not get ill.

Question 15

Which of the following pathogens/diseases would be the easiest to eradicate?

Accepted Answer

Pathogens that only infect humans and cause obvious signs and symptoms are easier to identify, isolate, and treat, reducing the spread and making eradication efforts more straightforward.

Question 16

Which pathogen is INCORRECTLY matched with a portal of exit?

Accepted Answer

E. coli is primarily excreted through feces, not urine. Urine can become contaminated with E. coli from the fecal matter, but the primary portal of exit for E. coli is the gastrointestinal tract, leading to excretion in feces.

Question 17

Which of the following best defines an endemic disease?

Accepted Answer

An endemic disease is one that is always present at some level in a population.

Question 18

The portal of entry of the pathogen causing illness in this case is the

Accepted Answer

The portal of entry of the pathogen causing illness in this case is the mouth. The pathogen enters the body through the mouth and travels to the large intestine, where it causes illness.

Question 19

Please identify the CORRECT statement regarding basic epidemiology concepts.

Accepted Answer

The answer of Please identify the CORRECT statement regarding basic...

Question 20

Which of the following is NOT a political/societal reason for a decrease in rates of childhood immunizations?

Accepted Answer

A lack of a proper "cold chain" for stable transport of vaccines into tropical areas is a logistical or infrastructure reason, rather than a political/societal reason. The other options all involve distrust or lack of faith in a certain entity related to vaccinations.

Quiz 19: Epidemiology