exam 1

Question 1

what is disease

Answer 1

any impairment that interferes with or modifies the performance of normal functions

Question 2

vector

Answer 2

living organisms that can transmit infectious pathogens between humans, or from animals to humans

Question 3

parasite

Answer 3

organisms that live on or in another organisms and depend on this host to complete their life cycle

Question 4

pathogen

Answer 4

a microorganism that causes damage to a host

Question 5

infectious disease

Answer 5

can be transmitted to/from another person or organism as a result of transmission of a biological agent

Question 6

infectious disease agents

Answer 6

living agents that cause harm while living in or on a host (viruses, bacteria, fungi, protozoa, helminths, arthropods)

Question 7

noninfectious disease

Answer 7

not transmitted directly, and instead are a result of a combination of environment and genetics

Question 8

noninfectious disease agents

Answer 8

nonliving agents (chemicals, toxicants, poisons), physical agents (cold, heat, trauma), nutrient deficiency (vitamin c, minerals, salts)

Question 9

zoonosis

Answer 9

disease caused by an infectious agent that can transferred naturally from wildlife to humans and back to wildlife

Question 10

what percent of emerging infectious disease in humans are zoonotic

Answer 10

60 - 75

Question 11

intrinsic causes of disease

Answer 11

genetic defects, degeneration

Question 12

extrinsic causes of disease

Answer 12

infectious/non infectious agents, noninfectious transmissible agents (prions)

Question 13

spillover

Answer 13

transmission of a pathogen from one host species to another

Question 14

amplifier

Answer 14

a host, within which, a pathogen replicates or is transmitted at rapid abundance or rate

Question 15

spillback

Answer 15

transmission of a pathogen from a spillover host back into the reservoir host from which it originated

Question 16

etiology

Answer 16

study or theory of the factors that cause disease

Question 17

cause

Answer 17

that which brings about a condition or produces any effect

Question 18

koch’s postulates

Answer 18

1. agent present in every case of the disease, not others
2. isolate agent, grown in pure culture
3. inoculate experimental animals with culture, develop disease
4. must recover the same agent from inoculated/infected animals

Question 19

exceptions to koch’s postulates

Answer 19

noninfectious diseases
mixed infections - tough to separate agents, know which is causing which part
carrier state - agent present, no disease
opportunistic agents - agents present and do not cause disease
chronic disease - the cause is gone before the disease appears

Question 20

emerging infectious disease

Answer 20

a disease that either has appeared and is affecting a population for the first time or has existed previously but is rapidly spreading in incidence or space

Question 21

incidence

Answer 21

rate of cases occurring during a particular time period

Question 22

web of causation

Answer 22

epidemiologic model that strongly emphasizes the concept of multiple causation while de-emphasizing the role of agents in explaining illness

Question 24

epidemiological triad

Answer 24

a simple model where the agent is not central focus causation includes interaction among host, agent, environment
applies to disease emergence and re-emergence

Question 25

what causes emergence

Answer 25

host - susceptibility pathogen - infectivity, virulence environment - stressors of conditions influencing hosts, pathogens, vectors, etc

Question 26

two strategies of detection

Answer 26

1. detecting the pathogen/parasite itself - microparasites, macroparasites 2. detecting disease - mainly searching for evidence of an immune response (blood/serum test), impairment of function, or clinical signs

Question 27

three steps of conducting a good study

Answer 27

1. state the question/hypothesis of interest clearly 2. these shape what data needs to be collected and hence the type of study 3. develop an appropriate plan for sampling

Question 28

the goal of sampling is to...

Answer 28

answer a research question in a way that is minimally biased and fairly precise

Question 29

population of interest

Answer 29

the complete collection of sample units of interest within a defined area (the sample frame) ex. individuals within a defined population or plots within a defined area

Question 30

sample

Answer 30

some fraction of the units within the population of interest are randomly selected data from the sample are used to estimate some parameter(s) of interest from the target population

Question 31

parameter

Answer 31

a quantitative measure that describes a characteristic of a population fixed quantity in a population; usually unknown ex. mean, sd, variance

Question 32

estimator

Answer 32

a formula, or function of the sample data used to estimate some parameter

Question 33

estimate

Answer 33

the value you calculate from the sample to estimate the parameter often denoted by a caret or hat (^) over the symbol

Question 34

bias

Answer 34

describes how far the average value of the estimator is from the true population value

Question 35

measures of quality of an estimate include

Answer 35

precision and prevalence

Question 36

precision

Answer 36

refers to the closeness of repeated measurements of the same quantity standard deviation (SD), standard error (SE), and coefficient of variation are all measures of precision ALWAYS report a measure of precision along with a parameter estimate (e.g., a confidence interval or SE on the parameter estimate)

Question 37

prevalence

Answer 37

proportion of hosts infected # currently infected / # in population

Question 38

types of random selection sampling

Answer 38

simple random and stratified random

Question 39

simple random sampling

Answer 39

every possible sample unit in the study area/sampling frame has an equal chance of being sampled during each sampling event; typically done without replacement - enumerate all possible sample units and take a random sample from the list

Question 40

stratified random sampling

Answer 40

the sampling frame is divided into mutually exclusive and exhausted strata (subgroups) and a simple random sample is taken from each stratum

Question 41

benefits of stratified random sampling

Answer 41

increased precision because variation among units within a stratum is < variation among units across strata allows for unique estimation of mean/variance for each strata allows for different numbers of sample units by strata