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126 Cards in this Set
- Front
- Back
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Epidemiology is the study of the
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distribution and determinants of health-related phenomenon in a population.
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The field of science concerned with the circumstances under which diseases occur.
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Epidemiology
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Factors under investigation in epidemiology:
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1. incidence (morbidity rate)
2. Prevention and control of infectious and noninfectious diseases 3. Effects of diseaseson opopulation and individuals within a population |
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This type of disease occurs irregularly and only occasionally in a population (ex. Typhoid fever)
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Sporadic Disease
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This type of disease occurs at irregular intervals but at low levels (ex. common cold, rhinovirus)
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Endemic disease
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This type of disease is when occurrence frequency rises, but not to epidemic proportions. (ex. common cold in the winter months).
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Hyperendemic disease
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Sharp increase in the incidence above the predicted/expected level
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Epidemic
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Natural location of the organism, can be animate or inanimate
(ex. dogs- rabies, malaria-humans) |
Reservoir
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A disease that can be transmitted from one human to another or from animals to humans.
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Communicable disease
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Many diseases, but not all, are ________
(ex. Measles is, but head colds are not). |
reportable
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The immediate location from which infectious agent has been transmitted.
(ex. Hep. C - transfusion, blood products) |
Source
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Hosts that harbor a pathogen without clinical symptoms and are capable of transmitting the infectious agent (sometimes unknowingly).
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Carriers
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A short carrier state is known as
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transient
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A long-term carrier state
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Chronic carrier
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Carrier state may also occur during which two periods?
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Incubation period
Covalescent period |
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The period before symptoms appear
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incubation period
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The period of recovery
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convalescent period
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A biological or inanimate source that contributes to the transmission of an infectious agent from one host to another. (e. anthropods, ticks - Lyme disease)
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Vector.
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Deals with animal diseases affecting animal populations.
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Epizootology
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Moderate incidence of epizootology
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enzootic
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Rapid increase of epizootology
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epizootic
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Wide spread of incidence in epizootology
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Panzootic
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If it is transferable to humans in epizootology
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Zoonoses
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A type of communicable disease that is transmissible from a vertebrate animal to man. Normally it is a disease of animals.
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Zoonosis
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Examples of zoonosis
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Rabies, anthrax, lyme disease, hantavirus
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What causes an infectious disease?
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A microorganism.
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Microorganisms may be a...
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bacteria, virus, or fungus.
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Risk factors for increasing emerging infectious diseases:
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drug resistance, preterm babies, immunosuppression, floods, droughts, deforestation
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What are the three conditions required for infection to spread?
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1. one person mustbe infected with a microorganism
2. The other person must be susceptible to infection with that microorganism 3. The microorganism must be able to leave the body of the infected person and enter the body of susceptible person. |
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A microorganism, chemical, nutritive, element or physical factor whose presence or absence is essential for a particular disease or condition to occur.
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Agent
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Types of agents
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Bacteria, protozoa, parasite
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Some host factors include
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1. Age, sex, ethnic group, nutritional status, socioeconomic status
2. Personal behaviors, smoking drinking diet sexual practices, exercise. 3. Immunization status: vaccinated or unvaccinated |
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The two goals of the epidemiologist are to
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control the spread or dissemination
eliminate etiological agent |
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Surveillance and data collection for control
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calculation of morbidity and mortality rates
case studies field studies |
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Observable or measurable change in body function.
ex. diarrhea, rash fever, vomiting |
sign
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Subjective
ex. pain, appetite loss, lethargy, depression |
symptom
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A set of sings and symptoms that is characteristic of a disease
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Disease syndrome
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The interval between the time of contact and/or entry of the agent and onset of illness.
The time required for the multiplication of microorganisms within the host up to a threshold where the parasitic population is large enough to produce symptoms. |
Incubation period.
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Different incubation periods have variable _____ and are present prior to _________.
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Lengths
development of signs and symptoms |
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The beginning of signs and symptoms, often infectious/contagious, innate immune response "kick in" (first line of defenses).
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Prodromal Stage
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Most severe phase, clear evidence of signs and symptoms, acquired immune responses begin.
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Illness stage
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Humoral immune responses:
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antibodies and conplement
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Cell-mediated responses:
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T cells instruct destruction of infected cells of destruction o intracellular bacteria.
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Alleviation of signs and symptoms, recover/coalescence
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Decline stage
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The Natural History of Disease
Pre-clinical phase (incubation period) Clinical phase: The person may become contagious before the onset of symptoms. |
1. infection
2. Disease could be detected through testing/screening 3. Symptoms of disease develop 4. Symptoms resolve or the infected person dies. |
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Shorter incubation periods, upper gastrointestinal symptoms
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Intoxications
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longer incubation periods, typically lower gastrointestinal symptoms
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Infections
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Staphylococcus occurs between the time periods of
- and - hrs. The symptoms of this are: There is no significant fever, but the body temperature often This is an example of an ______ |
1/2 hr to 8 hours, usually 2-4
cause: nausea, diarrhea, cramps, vomiting, temp often drops this is INTOXICATION |
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Salmonella:
occurs between - hrs. causes _______ with cramping, diarrhea, abdominal tenderness, vomiting, and fever. This is an _____ |
6-72 but usually 12-36
gastroenteritis Infection |
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Factors that play roles in the incubation period of a disease
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dosage of the infectious agent
portal of entry immune response of the host |
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Kissing, skin to skin contact and sexual intercourse are all examples of
(Also, plant or soil harboring infectious agents). |
direct contact
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Spray by short range aerosol, large droplets from coughing sneezing, talking, or singing
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Droplet spread
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The two forms of direct transmission are
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droplet spread and diect contact
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The three forms of indirect transmission are
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air borne
vehicle borne vector borne |
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Microbes, particles of droplet nuclei and dust suspend in the air
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air borne
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food, water, blood, tissues, organs and fomites
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vehicle borne
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disease transmission by a non-vertebrate host
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vector borne
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Inanimate objects capable of transferring infectious material
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fomites
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Bedding, toys, doorknobs, combs, clothing, drinking glasses, cooking utensils, pencils, straws, or surgical instruments are examples of
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fomites
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In vector borne transmission, an agent is carried by
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a live non-human carrier (vector).
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Most vectors are ________ (insects) such as mosquitoes, flies, ticks, or fleas, but they may be animals.
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arthropods
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Vector-borne transmission may be _____ and/or _____.
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mechanical, biological.
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in Mechanical Vector borne Transmission the vector is contaminated through
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mechanical means
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There is no multiplication of the agent within
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the vector
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Vector borne diseases include
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malaria, yellow fever, plague, typhus
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background cases; expected number of cases
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endemic
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excess number of cases in a localized area
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epidemic
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excess number of cases worldwide
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pandemic
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Sharp increase to a peak, then rapid resolution.
Associated with common contaminated source -food poisoning (food) -legionnaire's disease |
Common source epidemic
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Extended rise with a gradual resolution
frequently observed with one individual = the source -gradual dissemination, all susceptible individuals succumb # of susceptible individuals eventually decreases due to acquired immunity. -agent loses the ability to disseminate through the population. |
propagated epidemic
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Resistance a population acquires as a whole to infectious disease
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Herd Immunity
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The number of individuals that must be immune to prevent an epidemic outbreak of a disease is a function of
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infectivity of the disease
duration of the disease Proportion of susceptible individuals in the population |
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When 70% of the individuals in a population are immune, the propagation from individual to individual is not sustained and
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epidemics do not occur.
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The decreased possibility of a group or communityyu developing an epidemic because there is a specific level of immunity or resistance to that disease in the population
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Herd immunity
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opportunity for contact and transmission decreases as the number of immune individuals
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increases
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susceptible individuals benefit from an indirect
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immunity. (not self-made immunity)
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occurs when there are more cases than you'd expect in a given area or among a given population in a specific period of time.
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outbreak
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Steps to investigating an outbreak
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1. Verify the outbreak
2. Plot tan epidemic curve 3. Calculate attack rates 4. Determine the source of the outbreak 5. Recommend and implement control measures |
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Establish a case definition
-who (person) -what (symptoms) -where (place) -when (time) identify, confirm, and quantify cases determine if there's more cases than expected. |
Verify the outbreak
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First person that is sick
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index case
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people who get sick from being directly exposed to the agent
measured by attack rate |
primary case
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people who get sick from being exposed to a primary case
measured by secondary attack rate |
secondary case
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To plot an epidemic curve, graph the _____
x-axis = y-axis = interpret the _____ describe the pattern, determine the incubation period and perhaps.... Examine ..... |
curve
time of onset # of cases curve the mode of transmission outliers |
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The most common type of food-borne outbreak is in ....
this is for a large population with a short.... easier to identify the ...... example: bad potato salad at a picnic |
point source transmission
short exposure period incubation period |
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Several peaks of cases
difficult to characterize the -ex. refrigeration temperature is off all week in a reastaurant |
continueing source transmission
incubation period |
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When the cases start slowly, incubation period is estimated by the time between first case and the peak of cases, cases taper off slowly, example: west nile
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Vector borne diseases
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When calculating _______
it is an incidence rate, expressed as a percentage, calculated for different exposures or settings |
Calculate Attack Rates
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Attack rate =
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# ill / ill + well (100)
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To calculate RR -
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compare attack rate for exposed vs. unexposed
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Secondary attack rate =
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total number of cases -initial cases / number of susceptible persons in the group - initial case (s)
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A secondary attack rate is used to estimate the spread of
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disease in a family, household, dorm, or other group environment
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A secondary attack rate measures the
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infectivity of the agent and the effects of prevention
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Identify the most likely cause and investigate the source to prevent future outbreaks
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determine the source of the epidemic
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if there is no obviosu commonality, plot the geographic distribution of cases by
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residence/work/school/locaion/ and seek exposures.
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Control the present outbreak
prevent future similar outbreaks |
recommend control meausre
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A vast majority of outbreaks are
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food-borne
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an incident in which (1) two or more persons experience a similar illness after
(2) epidemiological analysis implicates the |
the investigation of a common good
food as the source of the illness |
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The three types of foodborne contamination
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physical
chemical biological |
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glass, metal fragments, sticks, dirt, bones, etc.
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physical contamination
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pesticides, cleaning compounds, poisonous metals, additives and preservatives
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chemical contamination
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bacteria, viruses, fungi, yeast, mold, parasites, poisonous fish and plants, insects and rodents
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biological contamination
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Major reasons for food-borne illness
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foods are cooled or reheated improperly
improper holding temperatures food handlers are infected poor hygeine cross-contamination |
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incubation period of:
2-4 hours |
staphylococcus aureus
cooked ham, meat, eggs, sauces, and gravies |
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12 hours
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clostridium perfringes
cooked meat, gravy |
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12-36 hrs.
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salmonella
meat, poultry, eggs |
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12-36 hrs
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clostridium botulinum
canned foods, smoked fish |
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12 hours
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vibrio parahemolyticus
raw fish, shellfish |
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24-48 hours
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shingella
contaminated by carrier, not foodborne |
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Which Food borne illeness has the highest percentage?
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Bacteria (40 agents)
-salmonella, staph aureus |
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What percentage is bacteria?
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68.7 %
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Most bacteria require a
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potentiall yhazardous food
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a potentially hazardous food is one that is high in
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protein and moist
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milk or egg products, eggs, meat, poultry and fine shellfish crustaceans, raw seed sprouts heat treated veggies and veggie products
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are potentially hazardous foods
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There is a systematic way to investigate
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outbreaks
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epidemic curves give us clues to the
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mode of transmission
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attack rates help determine the
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source of an outbreak
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food-borne outbreaks are a common problem and areoften the result of
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improper food handling and storage
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Epidemiological triad concepts
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virulence
pathogenic infectivity |
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All 3 epidemiological triad concepts are dependent on the condition of the host:
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immunity
butrition sleep hygiene |
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Measures the ability to invade a host
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infectivity
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Formula for infectivity
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number of infected / number of susceptible x 100
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measures the ability to cause disease
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pathogenicity
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formula for pathogenicity
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number with clinical disease/ number of infected x 100
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measures the severity of disease
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virulence
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formula for virulence
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number of deaths/ number of people with the disease x100
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Ability to become infected with an organism when exposed to it.
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susceptibility
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