1 Contamination is the presence on clothing or surface of the
body of the agent. With infection, the agent is within the body and [usually] multiplying.
2 Infections may or may not have signs
and symptoms. Infectious diseases are symptomatic, causing phsiologic
dysfunction.
3
See the list under agents on p. 62 and Table 3.1 on p. 63.
4 Cases,
carriers, animals, & inanimate objects
5 Cases demonstrate signs or symptoms; carriers do not demonstrate signs or symptoms.
6 Zoonotic
disease
7 Water, soil, food, air.
8 Cyclozoonoses
require two vertebrate hosts to complete their cycle (e.g., tapeworms). Direct
zoonoses travel directly from a non-human animal to a human (e.g., rabies).
9 Metazoonoses require invertebrate
intermediaries (e.g., insects) between vertebrate species.
10 "Sapro"
means "dead."
11 respiratory tract, conjunctiva, urogenital, gastrointestinal, skin, placenta
12
Direct contact transmission requires physical contact between a contagious and
susceptible host. Indirect contact requires contact between infectious material
and the susceptible host.
13 Droplets = large infectious particles transmitted via spray; droplet nuclei = small aerosolized particles suspended in air.
14 A
vector is a living transmitter (e.g., an insect vector). A vehicle is inanimate.
15 Mechanical transmission = no multiplication of agent in vector or vehicle; developmental transmission = agent undergoes
biological transformation or maturation in vector or vehicle.
16 With
developmental transmission, the agent undergoes a biological transformation in
the vehicle or vector. With propagative transmission, the agent multiplies in
the vehicle or vector.
17 The Broad Street pump outbreak was a common-source outbreak.
18 Respiratory
infections like the common cold are generally spread serially, from
person-to-person.
19 Understanding the biological cycle of an agent
permits multiple opportunities to disrupt the ecology of the disease. For
example, Fig. 3.1 shows the life cycle of the blood worm. The snail plays an
important developmental role in the life of the agent. If we can rid the
environment of this intermediate host (e.g., via drainage programs to rid the
environment of the snail ecosystem), we can prevent future occurrences of the
disease schistosomiasis.
20
Understanding the natural history of a disease in an individual may shed light
on periods of infectivity and susceptibility. It may also help us understand
routes of transmission and portals for infection (see last � on p. 67 and Fig.
3.2 (p. 69) for an illustrative example concerning HIV).
21 True.
22 immunization
23 Active immunization requires an immune response to the agent by the host.
24 therapeutic and maternal
25 This is called vaccination
26 Modified live vaccination generally
elicit the more sustained immune responses since the host is exposed to the antigen
challenge for a longer period of time.
27
cytokines [and chemokines].
28 B lymphocytes
29
T4 "helper cells" (a type of lymphocyte)
30 white blood cells (or, more
specifically, lymphocytes).
31 (a) High incidence of infectious diseases worldwide and emerging
and reemerging infectious diseases and (b) provided may original insights into
studying disease occurrence on a population basis (pp. 61-62)
1 Herd immunity is the proportion of the
population that is immune.
2 Acquired herd immunity requires exposure to the agent
and an active (physiologic) response on part of the herd (population) members.
3 A high prevalence of sickle cell anemia protects
against some forms of malaria.
4 If a high percentage of individuals are immune, transmission
can "dead end," preventing further spread.
5 Because the 13 immune individuals are not technically
at risk.