Question

QUESTION 7

On September 6, a six-year-old boy experienced fever, chills and vomiting. On September 7, he was hospitalized with diarrhea and swollen lymph notes under both arms. On September 3, the boy had been scratched and bitten by a cat. Chloramphenicol (a synthetic, lipid-based antibiotic that interferes with protein synthesis) was administered to the boy from September 7 when Yersinia pestis was isolated from the boy. On September 17, the boy’s temperature returned to normal and on September 22, he was released from the hospital.

If this youngster is exposed to Yersinia pestis in the future, it is a good bet that he will be immune to the bacterium and will not develop disease. This is best described as__________________.

1Naturally acquired active immunity

2Naturally acquired passive immunity

3Artificially acquired passive immunity

4Artificially acquired active immunity

QUESTION 8

Which of the following is not correctly matched?

1point source epidemic - outbreak in which the infection came from a single source

2common source epidemic - result of common exposure to a single source of infection over a period of time

3propagated epidemic - an outbreak that is transferred amongst people and is sustained in the population over time

4all of these are matched correctly

QUESTION 9

Suppose a strain of Norovirus breaks out at an elementary school. Norovirus is extremely contagious, but usually not serious. We would expect the ID50 value to be quite low and the LD50 value to be quite high in this instance.

1 True

2 False

QUESTION 10

Suppose a strain of Norovirus breaks out at an elementary school. Norovirus is extremely contagious, but usually not serious. When the number of Norovirus cases starts to decline we would also expect herd immunity to decline.

1 True

2 False

Answer 1

Answer 7:

Option 1- Natural acquired active immunity

Naturally acquired active immunity occurs when a person is exposed to a pathogen, develops disease, and as a result of primary immune response to the pathogen has acquired immunity.

Answer 8:

Option 4-All the definitions are matched correctly.

Answer 9:

Option1; True
ID50 means infectious dose when 50% of the exposed persons get infected. Since Norovirus is very contagious, the ID dose will be low. LD50 is Lethal Dose when 50% of those exposed succumb to infection. As Norovirus is infectious but not serious (or lethal), its LD50 must be very high.

Answer 10:

Option 2- False

Herd immunity describes the phenomena that individuals at risk are protected from the infection because they are surrounded by persons who are immune to the disease, thereby decreasing the chance of causative agent to spread among the herd. Even when the number of cases decline, the Herd immunity will remain intact and will become more strong by avoiding the re-emergence of the disease.