Bauman Chapter 25 Answers to Critical Thinking Questions
p. 705
As you have probably noticed, colds occur more frequently in the fall and winter. One
explanation for this observation is that more people are crowded together in buildings
when school starts and the weather cools. Design an experiment or epidemiological
survey to test the hypothesis that crowded conditions explain the prevalence of colds in
the fall and winter.
Recruit two otherwise matched (same genders, races, ages) groups of people who have
different winter patterns: One group (college students) spend most of the time indoors in
crowded rooms during the winter, while the other group spends most of the time
outdoors and little time in crowded rooms (postal carriers, trash pickup, delivery
services, etc.). Monitor the groups through the winter to see whether there is a
significant difference in the incidence of colds between the two groups.
p. 707
Smallpox is the only disease that has been eradicated worldwide, though scientists are
close to eradicating polio. What features do the smallpox and polio viruses share that
has allowed medical science to rid the world of these diseases? Compare these
features to those of rhinoviruses in discussing the likelihood of eliminating colds caused
by rhinoviruses.
Both viruses infect humans only, both are acute infections, and both have little genetic
variation so a single vaccine can be used against each. There are about 100
rhinoviruses, each antigenically distinct, making a vaccine that protects from infection by
all rhinoviruses extremely unlikely.
p. 713
Suppose a vaccine for dengue that induced the production of memory T cells could be
developed. After reviewing the characteristics of infection and reinfection, would you
argue for or against the use of such a vaccine? Why or why not?
A vaccine against one strain of dengue virus produces immunity to that strain, but does
not protect from infection with the other three strains, and will contribute to more severe
disease upon infection with one of the other three strains because dengue hemorrhagic
fever is a hyperimmune response following activation of T cells. If the vaccine does not
provide protection from all four strains at the same time, it should not be used.
p. 731
Ebola hemorrhagic fever belongs to a group of diseases called “emerging diseases”—
diseases that were previously unidentified or had never been identified in human
populations. Emerging diseases are often first seen in Third World countries such as the
DRC. What factors may explain the emergence of new diseases in these countries?
Third World countries have rapidly growing populations that expand into territory where
humans have not previously resided, and people are exposed to animals and vectors
that humans may not previously contacted. The increasing population also needs more
food. Food is sought in new places and sometimes new animals and plants become
food, exposing people to new pathogens. As the pressure from human encroachment
drives animals out or closer to extinction, the parasites and pathogens of those hardpressed animals venture into new hosts such as humans, sometimes successfully. The
absence of a public health infrastructure allows new diseases to spread before the
health care structure becomes aware of it.
p. 741
1. Chapter 4 presented the use of dichotomous keys to identify microorganisms.
Design a key for the RNA viruses discussed in this chapter.
Envelope?
Yes
No
Helical
capsid?
Yes
ds RNA
Yes
No
No
Capsid
less than
30 nm?
Reoviridae
+ sense
RNA
Yes
See *
Below
No
Yes
No
Picornaviridae
Coronaviridae
Segmented?
Yes
Yes
No
8 piece
genome?
Indentations
in capsid?
No
Calciviridae
Yes
No
Orthomyxoviridae
Hepatitis?
Yes
3 piece
genome?
No
Hepeviridae
Yes
Astroviridae
No
Bunyaviridae
*
Segmented?
Arenaviridae
Yes
No
Retroviridae
Bullet shape?
Yes
Flavivirus
gene
structure?
No
Rhabdoviridae
Flexible
virion?
Yes
Filoviridae
Yes
No
Paramyxoviridae
Flavivirdae
No
Togaviridae
2. A 20-year-old man is brought to a South Carolina hospital’s emergency room
suffering from seizures, disorientation, hallucinations, and an inordinate fear of
water. His family members report that he had suffered with fever and headache for
several days. The patient had been bitten by a dog approximately 12 days before
admission. What disease does the patient have? Will a vaccine be an effective
treatment? If the dog is found to be rabies free, what wild animals are the likely
source of a rabies infection in South Carolina? What treatment should the patient’s
family, coworkers, friends and caregivers receive?
The young man has rabies. The virus infection has progressed to the brain, a vaccine
will not be effective at this point. Raccoons are the primary reservoir of rabies along the
East Coast of the U. S. The patients’ contacts that may have come in contact with his
saliva should receive prophylactic treatment consisting of rabies vaccine and human
rabies immune globulin.
3.
How do coltiviruses get their name?
The name coltivirus is a condensation of Colorado tick virus.