Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
221 Cards in this Set
- Front
- Back
|
define epidemiology
|
the study of occurrence and distribution of disease in populations w/an emphasis on establishing the causal factors that influence disease occurrence and distribution, in order to determine and develop effective preventative and therapeutic protocols
|
|
|
objectives of epidemiology
|
-ID aetiology/cause or risk factors for dz
-determine extent of dz in herd/population -study natural history and prognosis of dz -evaluate efficacy of preventative and therapeutic measures that are used -develop foundation for developing COST-EFFECTIVE health policies to reduce or eliminate risk factors --> reduce/eliminate morbidity/mortality |
|
|
define pandemic
|
a widespread epidemic/epizootic involving more than one country
|
|
|
define endemic
|
the usual/constant frequency of a disease in a population
|
|
|
define epidemic
|
occurrence of a disease in excess of the expected/endemic level
|
|
|
what is included in macroepidemiology?
|
addresses global, international issues such as pandemics
|
|
|
what is included in microepidemiology
|
addresses national issues, small numbers
|
|
|
what is molecular epidemiology? what does it look at?
|
-interpretation of dz risk w/presence of susceptibility genes in population so allows for early evaluation of disease markers
-looks at the effect of genetic and environmental factors on disease risk -looking at the molecular level/strains of a virus |
|
|
genetic epidemiology encompasses what?
|
-genetic factors only (it is part of molecular epidemiology)
-specifically focuses on genetic factors involved in causation of disease |
|
|
define seroepidemiology
-examples |
epidemiological studies based on serological testing in detection of infection
-IFA test on serum samples from cattle to detect Neospora caninum as a cause of bovine abortion -serum samples from Japanese veterinary surgeons used to evaluate their risk in acquiring the zoonotic disease that is Q fever caused by the organism Coxiella burnetii |
|
|
define descriptive epidemiology
|
-study of the distribution of dz measure by incidence and prevalence of dz
-characterizes the burden of dz in the population |
|
|
define analytical epidemiology
|
-study of determinants of dz such as causal factors, host characteristics using relative risk and odds ratios
|
|
|
define clinical epidemiology
|
-application of epidemiological principles and methods to problems encountered in clinical practice
|
|
|
define evidence-based medicine (EBM)
|
the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of the individual patient
|
|
|
recent epidemics
|
-west nile virus
-BSE -SARS -highly pathogenic Avian Influenza |
|
|
examples of pandemics
|
-influenza in domestic birds
-E.coli in humans |
|
|
level of dz and its distribution in a popular is affected by what 3 things?
|
-temporal factors - time period this is occurring
-host factors (who, age, structure, breed, immune status -spatial factors - where, common or rare, climate |
|
|
4 ways dz occurrence can be reported
|
-time/temporal
-time series analysis -host related distribution of dz -space (spacial or geographical) location |
|
|
what is the epidemiological triangle?
|
based on the interplay between:
-agent -host -environment |
|
|
temporal dimensions of an endemic dz
|
-dz occurs at expected frequency
-dz present in population or region at all times -usually low or predictable level |
|
|
temporal dimensions of an epidemic dz
|
-dz occurs at greater than expected frequency
-in animals, occasionally referred as epizootic dz -occurrence depicted graphically as epidemic curves |
|
|
temporal dimensions of an pandemic dz
|
-huge epidemic (international)
|
|
|
temporal dimensions of an sporadic dz
|
-single case or small cluster of cases, infrequent dz occurrence
-irregular and unpredictable |
|
|
axes for the epidemic curves
|
Y-axis: number of new cases
X-axis: time |
|
|
3 basic types of epidemic curves
|
-point source epidemic
-continuous common source epidemic -propagating epidemic |
|
|
what is a point source epidemic curve used for?
-shape -what is it most commonly used for? |
large # of cases in a pop aof itnerest are exposed during a short time period (subjected to the same exposure over a limited, defined period of time, usually w/i one incubation period)
-shape: rises rapidly and contains a definite peak at the top, followed by a gradual decline (there is a rapid rise in disease then there are no new cases occurring when the point source is removed) -food-borne outbreak |
|
|
what are epidemic curves used for?
|
-develop hypothesis as to potential dz causes
-provide information on probably time of exposure based on the incubation period -provide information on source of outbreak (point, common, propagating) |
|
|
what is a continuous common source epidemic curve?
-shape -examples -how long is the incubation period? |
exposure to the source is prolonged over an extended period of time and may occur over more than one incubation period
-down slope of the curve may be very sharp if the common source is removed or gradual is the outbreak is allowed to exhaust itself -ex Legionnaires dz spread via and ac system or outbreak of cholera investigated by john snow in 1854 -usually 1-3 days |
|
|
what is a propagating epidemic curve?
-shape -examples |
occurs when dz is introduced through a single (primary) source of infection in one animsl and subsequently transmitted to other animals (secondary cases)
-shape: usualyl contains a series of successively larger peaks, reflective of the increasing number of cases caused by person-to-person contact, until the pool of secondary cases is exhausted or control measures are implemented -hepatitis A, E. coli spread by fecal-oral, new variant form of CJD (Creutsfeld-Jakob dz) linked w/BSCE in cattle) |
|
|
what is time series analysis?
|
-time series analysis uses the information on patterns of dz occurrence obtained from temporal occurrence data to ID periods of high or low risk (trends) so that causal associations could be explored
|
|
|
in a time series analysis, patterns of dz occurrence are influences by what 3 trends?
|
-short-term - typical epidemics
-cyclical (including seasonal) -secular trend (long term trend) |
|
|
cyclical trends (TSA)
-ex |
-rise and fall of dz over >1yr
-assoc w/regular, periodic fluctuations in level of dz occurrence -ex. 3-4 yr cycle of FMD in Paraguay |
|
|
seasonal trends (TSA)
-fluctuations/changes caused by ? -ex |
a special case of cyclical trends where the periodic fluctuations in dz incidence are related to particular seasons
-host density, management practices, vector dynamis, survival of infectious agents based on environmental factors -Rinderpest > in the dry season in africa, myxomatosis in rabbits peak in august and february in the UK, lepto in hot temperatures |
|
|
secular trends (TSA)
-ex |
-overall rises or decline in incidence occurring gradually over long time periods using plotted raw data and other statistical methods
-drop in CV dz risk factors by body mass index in adults that has occurred over the years |
|
|
what factors affect dz occurrence?
-rates are commonly adjusted for what three factors? -why? |
age, sex, breed, immune status, population dynamics
-age, breed, sex -they may interfere with an accurate comparison |
|
|
two things that measure dz occurrence
|
incidence and prevalence
|
|
|
define incidence
|
# of new cases occurring in a population over a defined period of time
|
|
|
equation for incidence (per 1000 individuals)
|
= [ (# of new cases of a dz in a population during a particular period of time) / (# of individuals at risk of developing the dz during that period of time) ] x 1000
|
|
|
how is incidence usually expressed?
-when is it calculated? |
as an incidence proportion within the population at risk
-only for the first occurrence of the dz in the individual |
|
|
define prevalence
-how is it expressed? |
# of cases present at any given point in time (snapshot)
-either as a proportion between ) and 1 or as a % or as a number per unit of population at risk |
|
|
equation for prevalence
|
= (# of individuals having a dz at a particular point in time (or a specified period of time)) / (# of individuals in the population at risk at that point in time (or specified period of time))
|
|
|
define point prevalence
|
prevalence at a point in time
|
|
|
define period prevalence
|
how many people have had the dz during a certain time period (ex over a calendar year)
-thus prevalence, unlike incidence, does not take into account the duration of dz - it is just a snapshot of a certain point in time |
|
|
prevalence is an important measure of what?
|
the burden of a dz in a population and is therefore useful in developing health policies
|
|
|
what is the relationship (equation) between incidence and prevalence?
|
prevalence = incidence x duration of disease
|
|
|
what is prevalence referring to?
what does prevalence help with? |
-interest in an existing cases of dz
-IDing major dz problems, IDing/evaluating control strategies such as vaccination, deworming |
|
|
what does incidence help with?
|
-to predict pop's health status (ex can use last years info to help predict this years)
-to assess the probability that an individual animal w/i a pop at risk may develop the dz of interest |
|
|
what is an attack rate?
|
measure of the propotion of the population that develops dz among the total exposed at the start of an outbreak
-refers specifically to outbreaks/epidemics |
|
|
what are the three steps of spatial distribution?
|
1. data visualization (putting data on a map and looking for patterns)
2. data description (see if the data is statistically significant) 3. data modeling (used to test hypothesis and plan health policies - model by relating to factors) |
|
|
who developed the unified concept of causation which is now generally accepted for IDing cause-effect relationships?
|
Evans
|
|
|
causal factors
|
-agent factors
-environmental influences -host factors |
|
|
agent factors:
|
-infection
-pathogenicity -virulence |
|
|
environmental factors
|
-temperature
-humidity -management practices |
|
|
host factors
|
-host susceptibility
|
|
|
what are the 8 major criteria for establishing cause
|
-strength of the association
-temporal relationship -dose-response relationship -biological plausibility -consistency -elimination -reversible associations -strength of study designs |
|
|
1. types of associations (there are 3)
2. what must be done (type 3) 3. a positive statistical association does what? (type 3) |
1. -non-statistical (by chance)
-risk factors (may be a causal factor of the dz in question or merely incr the likelihood of dz occurrence) -statistical (variables are statistically more frequently associated than by chance) 2. must conduct a statistical test of significance 3. MAY indicate a causal relationship |
|
|
3 types of risk factors
|
1. genetic
2. behavioral 3. environmental |
|
|
causal factors can be ?
|
-necessary and sufficient (dose of virus required to cause dz)
-necessary but not sufficient (multiple factors required to cause dz) -sufficient but not necessary -neither sufficient nor necessary but can contribute to dz |
|
|
types of epidemiological studies (from strongest to weakest) that provide evidence (NOT proof) that an association may be causal:
|
-randomized clinical trial (strongest)
-cohort and case controlled -cross sectional -cases series -case report (weakest) |
|
|
what do both the relative risk and odds ratios measure
-when is the odds ratio used? |
-strength of association - both compare risk of dz with exposure vs risk of dz w/o
-case-control studies (otherwise, RR is used) |
|
|
define bias
|
a systematic error in an epidemiology study that results in an incorrect estimate of the association between exposure and risk of dz
|
|
|
types of bias
|
-selection bias
-surveillance bias (assessment of dz may be better in the monitored pop than in the general pop) -misclassification bias (differential or non-differential) -information bias |
|
|
difference between the two types of misclassification bias
|
-differential/non-random: misclassification in determination of exposure or dz that occurs in different proportions in each group
-non-differential: occurs in the same proportion in each group (results from the degree of inaccuracy that characterizes how information is obtained from any study group - problem is in data collection methods NOT related to exposure or case/dz status) |
|
|
chance vs bias
|
chance = random error - low precision, reliability, repeatability
bias = systematic error - low validity, accuracy, correct value |
|
|
define confounding
|
the distortion or the masking of an association between an exposure and an outcome (or dz) bc of a third factor
|
|
|
ina study of whether Factor A is a cause of dz B, we sat that a third factor X is a confounder if the following are true:
|
-Factor X is a known risk factor for dz B
-Factor X is associated w/Factor A but is not a result of Factor A |
|
|
ways to control confounding
|
-randomization
-matching -restriction -stratification -multivariate analysis |
|
|
3 types of descriptive studies
|
-case reports/case series
-cross-sectional -correlation (ecologic) |
|
|
4 types of analytical studies
|
-prospective cohort
-retrospective cohort -case-control -randomized trial |
|
|
what do descriptive studies do?
|
characterize dz, quantify the burden of dz on a pop, describe pattern of dz
-(where, who, when, risk factors) |
|
|
difference between descriptive and analytical studies
|
descriptive: describe the occurrence of dz in populations
analytical: seek to ID and explain the causes of dz and usually assign a numerical value to (quantifying) the effect of a particular risk (exposure) factor |
|
|
case reports/series: what do they do and how are they written?
-what's different about case series (than a case report) -strengths |
describe a single case or group of cases, usually written as a clinical narrative
-case series IDs common features among a few cases and describes patterns of variability among them -quick, cheap, can be first indication of an epidemic or new dz |
|
|
cross sectional studies are aka
-what is it? |
Prevalence studies
-a snapshot of health at any defined point in time |
|
|
equation for prevalence of dz:
|
a/(a+b) OR c/(c+d)
-compared in exposed and non-exposed individuals |
|
|
equation for prevalence of exposure
|
a/(a+c) OR b/(b+d)
-compared in diseased and non-diseased |
|
|
ecologic studies are aka
-what do they evaluate -common approach -ex -where is the data found |
correlational or aggregate-level studies
-exposure and dz on a group level rather than on an individual level -look at geographical correlations -ex occurrence of TB in herds in Wales - may just be 1 animal found positive but entire herd is designated positive -from published stats about pop/herd (information of only some of the pop may be known) |
|
|
ecological fallacy
|
-if an assumption is made that the association found at the herd/group level is also true on the individual level
|
|
|
drawback(s) of ecologic study
|
cannot be used to determine cause of dz
-unable to link exposure to dz -unable to test hypothesis -unable to control for confounding factors |
|
|
observational analytical studies
|
cohort (prospective and retrospective) and case-control
|
|
|
non-observational analytical studies
|
clinical trials (intervention studies)
|
|
|
what is a cohort?
|
a cohort is a group of persons who share a common experience within a define time period (ex birth, marriage, etc)
|
|
|
how do you start a cohort study?
|
start by IDing an exposed cohort and an unexposed cohort
|
|
|
what do you do in a Prospective Cohort study?
|
select exposed and non-exposed groups and follow the cohorts forward and measure the amt of dz that occurs in each cohort (present to future)
-ex obesity (risk factor) and hypertension (dz state) - have an obese group and a non-obese groups and measure the amt of hypertension that arises in each |
|
|
what do you do in a Retrospective Cohort study?
|
from HISTORICAL RECORDS ID exposed and non-exposed groups then look at additional historical records to see how much dz developed in each cohort (past to present)
|
|
|
what question is asked when using relative risk/risk ratio?
|
how many time more (or less) likely are exposed individuals to get the dz relative to non-exposed individuals?
|
|
|
how to read relative risk ratio calculations
|
is RR is close to 1, the exposure is probably not associated with the risk of dz
-if RR >1, incidence of dz in exposed > incidence of dz in non-exposed -if RR <1, then exposure is associated w/decr risk of dz (protective) -the greater the distance from 1, the stronger the association |
|
|
when can relative risk ratios NOT be used
how to calculate relative risk ratios |
-case control studies
-RR = incidence exposed/incidence not exposed = [a/(a+b)/c(c+d)] |
|
|
how do we determine the statistical significance of risk ratio?
|
use confidence intervals or P values
|
|
|
different between statistical and clinical significance
|
clinical significance: affordable, able to use in a real life setting, does it make a different in mortality or morbidity enough to justify it's use?
|
|
|
what is the accepted level of confidence interval we want for any reported RR?
-what do CIs reflect? |
95%
-precision of the estimate of the RR (the wider the CI, the less precise the RR) |
|
|
when do we say the CI is statistically significant?
-when do we say it's not? |
when it falls on either side of 1
-when it includes 1 |
|
|
when are cohort studies useful?
|
when exposure is rare (ex animals exposed to very high radiation - chernobyl)
|
|
|
strengths of cohort studies
|
-can directly measure incidence
-useful when exposure is rare -can examine multiple outcomes of a single exposure -can describe temporal relationship between exposure and dz -if prospective, can collect data on possible confounders |
|
|
difference between case-control studies and cohort studies
|
case-control: start with dz as opposed to exposure
|
|
|
explain case-control studies
|
ID a group with the dz (cases) and a group w/o (controls) - determine the proportion of each that were exposed and not-exposed
|
|
|
how do you measure association in a case-control study?
|
Odds ratio (rather than the risk ratio)
|
|
|
what does a case-control study NOT estimate?
|
prevalence or incidence
|
|
|
what is the odds ratio used for in a case-control study?
|
to determine relative risk (just like the RR ratio though that's not used for case-control studies)
|
|
|
equation to calculate the Odds Ratio
|
(odds that cases were exposed)/(odds that controls were exposed) = (a/c)/(b/d)= (a*d)/(b*c)
|
|
|
which type of study will provide to strongest evidence of causality?
|
clinical trial
|
|
|
in clinical trials, the animals are divided into what 3 groups?
|
-treated control group
-untreated control group -placebo controls |
|
|
what is the difference between therapeutic trials and prevention trials?
|
-therapeutic: test agent pr procedure to diminish symptoms, prevent recurrence, or reduce risk of death
-prevention: evaluate whether agent or procedure reduces risk of dz developing in those currently free of dz |
|
|
often use what to do a cross-sectional study?
|
surveys
|
|
|
definition of validity
-validity of screening tests has two components: |
the ability of a test to distinguish those who have the dz and those who don't
-sensitivity: ability of a test to correctly ID those who DO have the dz -specificity: ability of a test to correctly ID those who do NOT have the dz |
|
|
true positives
|
those with the dz who are correctly called positive by screening test
|
|
|
true negatives
|
those w/o the dz who are correctly called negatives by screening test
|
|
|
false positives
|
those w/o the dz who are erroneously called positive by screening test
|
|
|
false negatives
|
those w/the dz who are erroneously called negative by screening test
|
|
|
what needs to be done w/tests of continuous variables?
|
must establish a cut-off above which a test result is considered positive and below which a result is considered negative
|
|
|
positive predictive value
|
if the test results are positive, what is the probability that the animals HAS the dz?
|
|
|
negative predictive value
|
if the test result is negative, what is the probability that the animal does NOT have the dz?
|
|
|
factors that affect the predictive value of a test
|
-dz prevalence in a given population
-specificity of the test |
|
|
calculation for positive predictive value of a screening test
|
(# true positives)/(# who tested positive)
|
|
|
calculation for negative predictive value of a screening test
|
(# of true negatives)/(# who tested negative)
|
|
|
factors affecting the predictive value (PV) of a screening test
|
-dz prevalence (the higher the prevalence, the higher the PV)
-specificity (incr in specificity will incr predictive value for infrequent cases) |
|
|
how must the results of a screening test be interpreted?
|
in the context of the prevalence of the dz in the population from which the subject originates
|
|
|
what factors contribute to variability/reliability/repeatability of tests?
|
-intrasubject variation (ex BP readings change throughout the day)
-interobserver variation (between those reading or interpreting results) -intraobserver variation (between 2 observations made by the same observer |
|
|
relationship between validity and reliability
|
ideal: want high validity (true values) and high reliability (reproducibility of results)
|
|
|
define: biological onset of dz
|
at this point there are no symptoms of dz - maybe a sub-cellular change in DNA
|
|
|
define: preclinical phase
|
time from onset to development of clinical signs/symptoms
|
|
|
define: detectable preclinical phase
|
at some point during preclinical phase, before symptoms deelop dz can be detected using screening tests
|
|
|
define: detectable phase
|
-from detectable preclinical phase (use of screening tests) to development of symptoms
|
|
|
screening tests are usually targeted towards ?
|
chronic dz - comparatively long preclinical phase
|
|
|
define: lead time
|
the interval by which the time of dx is advanced by early screening and early detection of dz compared w/the usual time of dx
|
|
|
infectious dz epidemiology involves understanding the relationship between ?
|
-infectious agent
-host -environment |
|
|
define: extrinsic incubation period
-what influences this period |
use w/vector-borne dzs and refers to the time period the agent requires in the vector before it is capable of inducing infection in the next host the vector encounters
-length of this period can be influenced by environmental conditions (ex temperature) |
|
|
define: latent period
|
time period between the initiation of infection in the host and when the host becomes infectious to others (first shedding)
|
|
|
define: period of transmission
|
time during which the host is infectious to others (agent being shed)
|
|
|
factors that influence transmission and interact to determine the pattern of infection
|
-reservoir
-host -vector -agent |
|
|
define: essential host (aka ?)
|
-aka reservoir host - a host required for maintenance and multiplication of the agent
|
|
|
define: amplifier host
|
hsot in which infectious agent multiplies to high levels sufficient to spread to other hosts
|
|
|
define: dead end host
|
host that cannot spread infection to other susceptible hosts under natural conditions
|
|
|
what happens in mechanical vectors?
|
-agent survives but no replication or development of pathogen in insect vector
-usually passed through passive manner (vector just carrying and accidentally dropped agent, etc) |
|
|
what happens in biological vectors?
|
replication or development of pathogen in the vector
-deliver to new hosts in active manner (usually a bite) |
|
|
define: perinatal infection
|
infant infected as it passes through the vagina (aka intrapartum)
|
|
|
in general, how are subclinical infection dx?
|
dx by serologic (antibody) response to culture of an organism
|
|
|
4 different outcomes of infection
|
1. sterile immunity - organism gone
2. carrier state - individual sheds the organism but is not usually infected (no evidence of Ab response) 3. latent state - time pd between initiation of infection in host and when host becomes infectious to others (individual usually infected) 4. persistent infection (chronic dz) - manifestation of symptoms many years after infection thought to have resolved |
|
|
define: disease
|
clinically apparent infection (infection accompanied by over illness)
|
|
|
pattern of infecctious dz is influenced by ?
|
1. environment (where/when) - season
2. host (who) 3. agent (what) |
|
|
define: herd immunity
|
resistance of a group, community, or population due to the introduction and spread of an infectious dz, based on the collective immunity of the group
|
|
|
the attack rate is used to measure what?
-generally used for what type of dz |
infectivity of an organism
-acute |
|
|
equation for attack rate
|
(# of new cases for epidemic period)/(population at risk)
|
|
|
how is a person-to-person-transmitted infection quantified?
|
secondary attack rate
|
|
|
define: index case
|
the person who became initially infected and serves as a source of infection to others
|
|
|
what does secondary attack rate measure?
-how is it usually measured? |
the probability that infection occurs among susceptible persons following known contact with an index case (primary case)
-in households or schools after exposure of susceptible contacts to an index case (high secondary attack rates are the principal reason childhood dzs are common) |
|
|
equation for secondary attack rate
|
(# new cases (derived from index case))/(all those that came into contact with the index case that remained healthy)
|
|
|
define: pathogenicity
-how it is quantified/equation |
ability of a pathogen to induce dz
- (# infected and exhibiting dz)/(total # infected) |
|
|
define: virulence
-how is it quantified/equation |
the ability of an agent to induce severe or fatal dz
- (# w/severe dz)/(total # w/dz) |
|
|
if death is a possibility, virulence is commonly known as ?
-how is this measured/equation |
case fatality rate
- (# fatal cases)/(# total cases) |
|
|
equation for mortality rate
|
(# deaths in a pop)/(# individuals in the total pop)
|
|
|
define: immunogenicity
|
the ability of an agent to induce an immune response, measured by Ab production
|
|
|
what is the case definition of "diseased" based on?
|
both clinical syndrome and laboratory data (agent and/or immune response) and detection of the agent
|
|
|
what is IgM indicative of?
|
recent infection
-elaborated during acute response to infection |
|
|
what is IgG indicative of
|
past (recent or distant) infection of long duration
-elaborated later in the course of infection |
|
|
what is herd immunity?
|
the point at which the number of animals in a given pop that have acquired immunity is so great, that under natural conditions a contagious agent cannot enter and spread within the herd
- # of immune animals dominate the herd |
|
|
in herd immunity, endemicity of an infection is determined by the balance between what?
|
-balance between # of immune animals in the herd and rate of addition of susceptibles
|
|
|
the 8 ways to sustain herd immunity
|
-active, adaptively managed, global coordination
-a robust, efficacious, safe, and affordable vaccine -an independent vaccine quality assurance service -robust, affordable diagnostic tests -and international accreditation mechanism operated by the Office International des Epizooties -guidelines for surveillance combined w/performance indicators (ex the WHO's) -molecular characterization of virus -designation of a world reference laboratory, hosted by the UK Institute for Animal Health |
|
|
dangers of mass vaccination
|
-vax can be a source of other agents and their use can have serious effects
-used w/o full understanding, attenuated vax can have serious and unexpected effects -use of a live virus has risk bc they may retain the capacity to cause the dz they are designed to prevent -can revert to virulence |
|
|
define: outbreak
|
-observed # of cases exceeds expected #
-specific area (spatial) -among specific group (demographic) -over particular time period (temporal) |
|
|
3 phases of outbreak investigation
|
1. descriptive (dz parameters, herd hx, case definition, epidemic curve)
2. analytical 3. intervention and control |
|
|
the 3 components of case definition in an outbreak
|
1. clinical signs
2. immunologic response 3. detection of the agent |
|
|
axes for epidemic curve when investigating an outbreak
|
# of cases vs onset of illness
-provides info on the probably time of exposure based on incubation period -provides info on whether outbreak was due to common or point source |
|
|
what is done during the analytical phase of outbreak investigation?
|
-generate and test a hypothesis
|
|
|
what is done during the intervention phase of outbreak investigation?
|
Timely implementation of appropriate measures to minimize further morbidity, mortality and national expenditure
|
|
|
3 major disasters of biological origin are
|
1. naturally occurring
2. accidental disasters 3. intentional/purposeful biological attacks (bioterrorism, agroterrorism) |
|
|
what was caused by the FMD and BSE outbreaks in the UK?
|
-economic devastation
-psychological impact -improved preparedness |
|
|
what dz in 2003 caused a psychological impact from 70 human cases of infection from infected prairie dogs?
|
monkey pox
|
|
|
what was improved as a result of the FMD outbreak in the UK
|
1. surveillance at ports
2. training of PH vets in responding to disasters 3. biosecurity on farms and at dx labs 4. worldwide surveillance improved |
|
|
the monkeypox, FMD, and BSE outbreaks were all what?
|
naturally occurring disasters
|
|
|
name one agent that causes a lot of food-borne illnesses
|
E. coli O157
|
|
|
when did E coli become nationally notifiable?
-it has been related to outbreaks in what product for how long? |
1994
-beef, the last 10 years |
|
|
what is the incr in reported number of E coli outbreaks due to?
|
incr lab ability to ID it
|
|
|
when were the 2 major outbreaks of E. coli in canada?
|
2000 & 2005
|
|
|
when was the e coli outbreak in the UK?
|
2009
|
|
|
3 major disasters of biological origin are
|
1. naturally occurring
2. accidental disasters 3. intentional/purposeful biological attacks (bioterrorism, agroterrorism) |
|
|
what was caused by the FMD and BSE outbreaks in the UK?
|
-economic devastation
-psychological impact -improved preparedness |
|
|
what dz in 2003 caused a psychological impact from 70 human cases of infection from infected prairie dogs?
|
monkey pox
|
|
|
what was improved as a result of the FMD outbreak in the UK
|
1. surveillance at ports
2. training of PH vets in responding to disasters 3. biosecurity on farms and at dx labs 4. worldwide surveillance improved |
|
|
the monkeypox, FMD, and BSE outbreaks were all what?
|
naturally occurring disasters
|
|
|
define: terrorism
|
includes the unlawful use of force and violence against persons or property to intimidate or coerce a government, the civilian population, or any segment thereof, in furtherance of political or social objectives
|
|
|
define: bioterrorism
|
the threat or use of biological agents by individuals or groups motivated by political, religious, ecological, or other ideological objectives
|
|
|
BioWatch cannot detect what?
|
pathogens released indoors on subways, planes, or buses
|
|
|
name the 3 categories of CDC agents
|
Category A (highest)
Category B Category C |
|
|
good agents to use for bioterrorism
|
B. anthracis
Y. pestis Coxiella burnetii Francisella tularensis |
|
|
List the main CDC Category A agents
|
-Ebola virus (person to person, no tx or vax)
-B. anthracis -Yersinia pestis (plague) |
|
|
List the main CDC Category B agents
|
-Brucella spp
-Coxiella burnetii (Q fever) -Salmonella, E. coli O157, Shigella |
|
|
List the main CDC Category C agents
|
-Nipah virus
-Hanta virus -various tickborne dzs |
|
|
what makes an agent a CDC Category A?
|
they are high priority agents that pose a risk to national security bc they:
-can be easily disseminated or transmitted from person to person -result in high mortality rates and have the potential for major PH impact -cause public panic -require special action for PH preparedness |
|
|
what makes an agent a CDC Category B?
|
-moderately easy to disseminate
-result in moderate morbidity rates and low mortality rates -require enhanced diagnostic capacity and dz surveillance |
|
|
what makes an agent a CDC Category C?
|
-third highest priority agents include emerging pathogens that could be engineered for mass dissemination in the future bc of availability
-ease of prod'n and dissemination -potential for high morbidity and mortality rates and major health impacts (not a lot of known about then bc they're emerging) |
|
|
how to make a pathogen more effective by weapon:
|
-enhance transmission
-incr virulence -make resistant to antibiotics -enabling it to be resistant to immunizing individuals by vax -altering the CS is effects |
|
|
which agent is spread through direct contact?
|
anthrax (scratches)
|
|
|
which agent is spread thru fleas?
|
plague
|
|
|
which agents are waterborne?
|
-crytosporidium
-giardia -E. coli -salmonella |
|
|
tell me about the plague
|
-organism: Yersinia pestis
-transmission: Y. pestis blocks GI tract of fleas --> regurgitate bacteria as they try to feed --> inoculate host (rodent fleas - cat and dog fleas not efficient hosts) -can also get from infection tissues/fluids of dead/sick animals (20%) or aerosol (2%) from humans (uncommon) or CATS |
|
|
tell me about pneumonic plague
|
-secondary - usually caused by spread of bubonic form to lungs (respiratory distress)
-primary - caused by inhalation ot aerosol droplets from other infected humans -w/o tx, fatal -tx required w/i 18-24 hrs of respiratory signs |
|
|
which form of the plague is most likely to be used for bioterrorism?
|
pneumonic plague - primary or secondary
-primary pneumonic form - person to person transmissible, aerosol -result of hematogenous spread to lungs from bubonic or septicemic plague |
|
|
plague reservoirs
|
primarily wild rodents (ground squirrels, prairie dogs, etc)
|
|
|
transmission of plague to cats
|
-bite from infected flea
-eating infected rodent |
|
|
animals resistant to plague
|
farm animals and dogs seem to be very resistant
|
|
|
true or false: dogs and cats cannot carry plague infected fleas
|
false: they can carry plague infected fleas but dog and cat fleas are not efficient vectors
|
|
|
signs of the plague in cats
|
-come from bubonic, septicemia, pneumonic
-mimic human illness - fever, lethargy, anorexia, DIC, death |
|
|
tx of plague in animals
|
gentamycin (choice) but doxycycline and chloramphenicol may be used
|
|
|
who may be the first to show signs with bioterrorism agents?
|
animals
|
|
|
define: agroterrorism
|
when any person knowingly or maliciously uses biological or chemical agents as weapons against the agriculture industry and food supply
|
|
|
an agent is chosen for agroterrorism attack bc it:
|
-is easily obtainable, cultures, or dispersed
-causes illness and death in target animal or human populations -causes economic hardship to a community/nation -has been previously used as an agent -a low dose is required to cause dz |
|
|
why do animal dz organisms make good terrorism agents?
|
-little technical training, low cost, high impact
-potential for rapid spread -difficult to trace -global source of raw material |
|
|
why are agroterrorism events so difficult to deal with?
|
-multiple points of entry
-multiple possible delivery methods -natural vs intentional vs accidental -real vs hoax |
|
|
goal of agroterrorism
|
economic and trade disruption
|
|
|
-% of US gross domestic product (GDP) = food and fiber
-% of total workforce deals with food and fiber |
-16% GDP
-17% workforce |
|
|
what is considered an indirect transmission route?
|
-vehicle-borne
-vector-borne |
|
|
true or false: nearly all effective agroterrorism agents pose little to no threat to the terrorist
|
true
|
|
|
the plague is rarely transmissible from human-to-human unless in what form?
|
pneumonic
|
|
|
highest priority agent on the "Select Agent List" for agroterrorism
|
FMD
|
|
|
agents on the high priority "Select Agent List" for agroterrorism
|
-FMD
-classical swine fever -newcastle dz -vesicular stomatitis -highly pathogenic avian influenza |
|
|
the main threat to livestock seems to be ?
|
naturally occurring outbreaks (esp emerging dzs)
|
|
|
List the 7 US federal food agencies
|
-US Dept. of Agriculture (USDA)
-Food and Drug Administration (FDA) -Environmental Protection Agency (EPA) -National Marine Fisheries Service -Dept of Homeland Security -Department of Defense -Centers for Disease Control and Prevention (CDC) |
|
|
what's the most important agency when dealing with outbreaks in humans?
|
CDC
|
|
|
what's the gov't organization that vets are most involved with?
|
USDA-APHIS (animal and plant health inspection service)
|
|
|
international agencies
|
-World Organization for Animal Health (OIE)
-WHO -FAO -PAHO |
|
|
key aspects to emergency management of foreign animal dzs
|
-biosecurity measures
-early detection -unusual signs (animals as sentinels of dz) -rapid reporting -rapid response by ALL involved agencies, private vets, etc -prompt quarantine -quick dz -depopulation of affected animals -continuing surveillance |
