Question 1

Which of the following best explains why measles is considered one of the most contagious diseases known?

Accepted Answer

It spreads via both droplet and airborne transmission, and one infected person can infect 12–18 others.

Question 2

A child recovers from measles but later develops frequent bacterial infections. What is the most likely explanation for this increased susceptibility?

Accepted Answer

Immune amnesia caused by measles infection leads to loss of preexisting immune memory.

Question 3

Which of the following is a hallmark diagnostic sign of measles?

Accepted Answer

Koplik’s spots in the mouth

Question 4

Why is a two-dose immunization schedule for the measles vaccine necessary to achieve herd immunity?

Accepted Answer

Two doses are required to reach the 90–95% coverage needed to prevent outbreaks.

Question 5

A patient presents with an expanding red rash resembling a bull’s-eye, malaise, and joint pain after a hiking trip. Which pathogen is most likely responsible?

Accepted Answer

Borrelia burgdorferi

Question 6

Which of the following best describes the mechanism by which Borrelia burgdorferi evades the host immune system in Lyme disease?

Accepted Answer

It undergoes antigenic variation by changing outer surface proteins (Osp).

Question 7

Why might a patient with Lyme disease test negative for antibodies against Borrelia burgdorferi during the early phase of infection?

Accepted Answer

Antibodies take more than 4–6 weeks to develop after infection.

Question 8

Which of the following is a recommended prevention strategy for Lyme disease in endemic areas?

Accepted Answer

Applying DEET-containing repellents and removing ticks promptly

Question 9

A 17-year-old presents with severe sore throat, fever, swollen lymph nodes, and extreme fatigue. Blood smear shows large, lobed B lymphocytes with atypical nuclei. Which pathogen is most likely responsible?

Accepted Answer

Epstein-Barr virus

Question 10

Which of the following statements about infectious mononucleosis is correct?

Accepted Answer

It is caused by Epstein-Barr virus, which becomes latent in B lymphocytes.

Question 11

Which of the following best explains why children under 6 years old typically experience mild symptoms when infected with Epstein-Barr virus?

Accepted Answer

Their immune system is immature, leading to less vigorous cell-mediated responses.

Question 12

Which of the following is a key virulence factor of Plasmodium species that contributes to malaria pathogenesis?

Accepted Answer

Ability to reproduce within red blood cells, avoiding MHC presentation

Question 13

A patient who recently traveled to a malaria-endemic region presents with cyclic fevers, chills, and anemia. Which stage of the Plasmodium life cycle is responsible for these symptoms?

Accepted Answer

Erythrocytic cycle in human red blood cells

Question 14

Which genetic trait provides resistance to severe malaria by altering the structure of hemoglobin?

Accepted Answer

Heterozygosity for the sickle cell gene (HbS)

Question 15

Which of the following is the most effective method for diagnosing malaria in a symptomatic patient?

Accepted Answer

Microscopic examination of blood smears for ring forms in erythrocytes

Question 16

A traveler to sub-Saharan Africa wants to prevent malaria. Which of the following strategies is most effective?

Accepted Answer

Using insecticide-treated bed nets and taking prophylactic antimalarial drugs

Question 17

Which of the following best explains why patients with malaria often develop jaundice?

Accepted Answer

The inability of the liver to process large amounts of hemoglobin released from lysed erythrocytes.

Question 18

Which of the following statements about the epidemiology of malaria is correct?

Accepted Answer

Humans are the only reservoir for human malaria.

Question 19

Which of the following is a reason why the measles virus is a candidate for eradication?

Accepted Answer

It only infects humans and an effective vaccine exists.

Question 20

A patient with late-stage Lyme disease experiences severe fatigue, joint pain, and depression. Why is treatment at this stage often less effective?

Accepted Answer

Symptoms are often caused by the immune system rather than active infection.

Microbial Systemic Diseases and Immune Interactions (Chapter 21): Measles, Lyme Disease, Mononucleosis, and Malaria

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