Question 1

In the 1999 West Nile virus outbreak in New York City, which of the following pieces of evidence suggested that the pathogen under investigation was not St. Louis encephalitis (SLE)?

Accepted Answer

A)   The time characteristic was not suggestive of SLE.
B)   There was no mosquito involvement in this disease, as there would have been for SLE.
C)   The viral particles were too small to be SLE.
D)   Control measures initiated to control a SLE outbreak were not effective.
E)   The case-control study indicated that this was not SLE. C

Question 2

The incidence of disease:

Accepted Answer

A)   is the total number of cases of a particular disease during an epidemic.
B)   is calculated by subtracting the number of recovered individuals from the number of sick individuals.
C)   is the number of new cases of a particular disease during a specified time period.
D)   is the period of time measured in days, weeks, or years, during which an epidemic occurs.
E)   is the average number of new cases infected by a single sick individual for a specific disease. C

Question 3

Which of the following pathogens would most likely be used as a bioterrorism agent?

Accepted Answer

A)   Pathogen A: an obligate anaerobe
B)   Pathogen B: an obligate aerobe
C)   Pathogen C: a Gram-positive bacterial species
D)   Pathogen D: a RNA virus
E)   Pathogen E: a spore-former E

Question 4

In which of the following types of viruses is antigenic shift most likely?

Accepted Answer

A)   RNA viruses
B)   DNA viruses
C)   enveloped viruses
D)   non-enveloped viruses 
E)   viruses with a segmented genome

Question 5

Which of the following is a characteristic of a commonsource epidemic?

Accepted Answer

A)   Once the source is identified and controlled the last cases will occur approximately one incubation period later.
B)   Once the source is identified and controlled there should be no additional cases.
C)   The time between identification and control, and the last cases, depends on the transmission rate between sick and susceptible individuals.
D)   When a common source epidemic begins, the number of cases rises slowly relative to a host-to-host epidemic.
E)   When a common source epidemic ends, the number of cases falls slowly relative to a host-to-host epidemic.

Question 6

How can a vaccine program prevent epidemics?

Accepted Answer

The answer of How can a vaccine program prevent epidemics?...

Question 7

When a new disease appears, which of the following is developed first?

Accepted Answer

A)   a case-control study
B)   personal characteristics of the disease
C)   place characteristics of the disease
D)   time characteristics of the disease
E)   a case definition

Question 8

Epidemic paralytic polio:

Accepted Answer

A)   was more likely when newborns were exposed to the virus.
B)   was more likely when exposure was delayed beyond infancy.
C)   was most commonly seen in situations where sanitation was poor.
D)   was eradicated in the United States as routine sanitation became commonplace.
E)   has not been observed since the 19th century in developed countries.

Question 9

Into which category of emergent diseases would dengue be placed?

Accepted Answer

A)   Category 1: invasion of a new host population by a known pathogen
B)   Category 2: appearance of a completely new, previously unknown pathogen
C)   Category 3: association of a well-known disease with a new pathogen
D)   Category 4: increased virulence, or a renewed problem, with a well-known but previously less virulent or well-controlled pathogen

Question 10

What is antigenic drift? Why are RNA viruses more prone to this phenomenon than DNA viruses are?

Accepted Answer

The answer of What is antigenic drift? Why are RNA...

Question 11

Describe the design of a case-control study and how it is used to identify the cause of an epidemic.

Accepted Answer

The answer of Describe the design of a case-control study...

Question 12

A particular type of virus occasionally undergoes antigenic shift. In which of the following situations is antigenic shift most likely?

Accepted Answer

A)   when RNA polymerase makes a mistake, introducing an incorrect nucleotide
B)   when the proofreading ability of RNA polymerase does not function properly
C)   when a particular host cell is infected by a single strain of the virus
D)   when a particular host cell is infected by two strains of the virus at the same time
E)   when the proportion of immune individuals in the population is low

Question 13

The likelihood of a host-to-host epidemic is highest when:

Accepted Answer

A)   the proportion of immune individuals in a population is below the epidemic threshold.
B)   the proportion of immune individuals in a population is above the epidemic threshold.
C)   the proportion of immune individuals in a population is at the epidemic threshold.
D)   anytime the proportion of immune individuals in a population rises above 50%.
E)   the second time a pathogen is introduced into a particular population.

Exam 13: Epidemiology: Who, What, When, Where, and Why

In the 1999 West Nile virus outbreak in New York City, which of the following pieces of evidence suggested that the pathogen under investigation was not St. Louis encephalitis (SLE) ?