epidemiology- definition Flashcards
Epi- upon
Demos- people
Logos- study of
study of what befalls a population
epidemiology
- Scientific inquiry and its foundation
- Data driven
- Relies on systemic, unbiased approach to the collection analysis and interpretation of data
study
- frequency
- pattern
distribution
- Why
- How
- Epidemiologists assume that illness does not occur randomly in a population, but happens only when the right accumulation of risk factors or determinants exists in an individual.
- To search for these determinants, epidemiologists use analytic epidemiology or epidemiologic studies to provide the “Why” and “How” of such events.
- They assess whether groups with different rates of disease differ in their demographic characteristics, genetic or immunologic make-up, behaviors, environmental exposures, or other so-called potential risk factors.
Determinants
- number of health events (number of cases of meningitis or diabetes in a population)
- relationship of that number to the size of the population.
- The resulting rate allows epidemiologists to compare disease occurrence across different populations.
Frequency
occurrence of health-related events by:
- time
- place
- person
Pattern
may be annual, seasonal, weekly, daily, hourly, weekday versus weekend, or any other breakdown of time that may influence disease or injury occurrence.
Time patterns
include geographic variation, urban/rural differences, and location of work sites or schools.
Place patterns
include demographic factors which may be related to risk of illness, injury, or disability such as age, sex, marital status, and socioeconomic status, as well as behaviors and environmental exposures.
Personal characteristics
Epidemiology was originally focused exclusively on epidemics of communicable diseases but was subsequently expanded to address endemic communicable diseases and non-communicable infectious diseases
Health-related states or events
- Clinician: is concerned about the health of an individual. clinician’s “patient” is the individual.
- Epidemiologist is concerned about the collective health of the people in a community or population. epidemiologist’s “patient” is the community.
Specified population
- applying the knowledge gained by the studies to community-based practice.
- make the proper diagnosis and prescribe appropriate treatment for a patient, the clinician combines medical (scientific) knowledge with experience, clinical judgment, and understanding of the patient
Application
a phase of epidemiology approach that concerns with the disease distribution and frequency
descriptive epidemiology
a phase in epidemiology approach that’s concerned with analyze the causes of disease through hypothesis testing
analytical epidemiology
phase epi approach that answers questions about the effectiveness of new methods for controlling diseases or for improving underlying conditions
intervention / experimental
phase in epi approach that measure the effectiveness of different health services and programmes
evaluation epidemiology
presumptive identification of unrecognized diseases or defects through the application of diagnostic tests or laboratory examinations and clinical assessment.
screening
done to look for previously unidentified cases of diseases.
case finding
proportion of persons with a disease who test positive on a screening test. measures the probability of correctly identifying a positive case of a disease.
sensitivity
proportion of persons without a disease who have negative results on a screening test. It measures the probability of correctly identifying non-cases.
Specificity
used to calculate an identifiable population exposed to an infectious agent. It represents the incidence of the illness among the exposed population. They are frequently used in surveillance and control of communicable diseases.
attack rate
basis for determining the community’s reaction against disease invasion since it represents the immunity and susceptibility levels of individuals comprising the population
herd immunity
situation when there is a marked upward fluctuation in disease incidence
epidemic
represents opportunities for progressive transfer of an infectious agent to a susceptible host and depends on:
1. frequency of contact
2. facility of transmission.
exposure/ contact rate
probability of contact between the source of infection and the depends upon the number of immunes and location of the source of infection.
chance
a. Common source epidemic is characterized by simultaneous exposure of a large number of susceptible to a common infectious agent
b. Propagated epidemic is caused by a person-to-person transmission of disease agent
fluctuations
any organism that harbors and provides nourishment for another organism.
host
intrinsic property of microorganism to survive and multiply in the environment.
agent
infectious agent or its toxic component that is transmitted from the source of infection to the susceptible body.
causative agent
sum total of all external condition and influences that affects the development of an organism which can be biological, social and physical. Affects both host and agent
environment
the intermittent occurrence of a few isolated and unrelated cases in a given locality. The cases are few and scattered, so that there is no apparent relationship between them and they occur on and off, intermittently, through a period of time.
Example:
Rabies occurs sporadically in the Philippines. In a given year, there are few cases during certain weeks of the year, while there are no cases at all during the other weeks. During the weeks when the few cases are occurring, the cases are scattered throughout the country, so that the cases are not related at all to the cases in other area.
sporadic occurrence
is the continuous occurrence throughout a period of time, of the usual number of cases in a given locality. The disease is therefore always occurring in the locality and the level of occurrence is more or less constant through a period of time. The level of occurrence maybe low or high, when the given level is continuously maintained, then the pattern maybe low endemic or high endemic as the case maybe. The disease is more or less inherent in that locality, it is a way already identifiable with the locality itself.
Example:
Schistomiasis is endemic in Leyte and Samar, Filariasis is endemic in Sorsogon, Tuberculosis is endemic practically in all specific areas of the country.
endemic occurrence
is of unusually large number of cases in a relatively short period of time. There is disproportionate relationship between the number of cases and the period of occurrence, the more acute is the disproportion, the more urgent and serious the problem is. The number of cases is not in itself necessarily big or large, but such number of cases when compared with the usual number of cases may constitute an epidemic in a given locality, as long as that number is so much more than the usual number in that locality. It is therefore not the absolute largeness of the number of cases but its relative largeness in comparison with the usual number of cases which determines an epidemic occurrence.
Example:
bird’s flu in any area of the country, so that the occurrence of few cases in a given area in a given time would constitute a bird flue epidemic.
epidemic occurrence
the simultaneous occurrence of epidemic of the same disease in several countries. It is another pattern of occurrence from an international perspective.
pandemic
systematic approach of obtaining, organizing, and analyzing numerical facts so that conclusions may be drawn from them.
statistics
systematic study of vital events such as births, illnesses, marriages, divorce, separation and deaths.
vital statistics
**Statistics on population and the characteristics such as age and sex, distribution are obtained from the National Statistics Office (NSO).
**Births and deaths are registered in the Office of the Local Civil Registrar of the municipality or city. In cities, births and deaths are registered at the City Health Department.
shows the relationship between a vital event and those persons exposed to the occurrence of said event, within a given area and during a specificied unit of time, it is evident that the person experiencing the event (Numerator) must come from the total population exposed to the risk of same event (Denominator).
rate
used to describe the relationship between two numerical quantities or measures of events without taking particular considerations to the time and place. These quantities need not necessarily represent the same entities, although the unit measure must be the same for the numerator and denominator of the ratio.
ratio
referred to the total living population. It must be presumed that the total population was exposed to the risk definitely exposed to it.
crude / general rate
the relationship is for a specified population class or group. It limits the occurrence of the event to the portion of the population definitely exposed to it.
specific rates
measure of one characteristic of the natural growth or increase of a population.
Total No. of live births registered in a given calendar year
CBR = Estimated population as of July 1 of the same year X 1000
crude birth rate
measure of one mortality from all causes which may result in a decrease of a population.
Total No. of deaths registered in a given calendar year
CDR = Estimated population as of July 1 of the same year X 1000
crude death rate
measures the risk of dying during the 1st year of life. It is a good index of the general health condition of a community since it reflects the changes in the environment and the medical condition of a community.
Total No. of deaths under 1 year of age registered in a given calendar year
IMR = Total No. of Registered live births of same calendar year X 1000
infant mortality rate
measures the risk of dying from causes related to pregnancy, childbirth and puerperium. It is an index of the obstetrical care needed and received by women in a community.
Total No. of deaths from maternal causes registered in a given year
MMR = Total No. of Registered live births of same calendar year X 1000
maternal mortality rate
measures pregnancy wastage. Death of the product of conception occurs prior to its complete expulsion, irrespective of duration of pregnancy.
Total No. of fetal deaths registered in a given calendar year
FDR = Total No. of Registered live births of same calendar year X 1000
fetal death rate
describes more accurately the risk of exposure of certain classes or groups to particular diseases. To understand the forces of mortality, the rated should be made specific provided the data are available for both the population and the event in their specifications. Specific rates render more comparable and thus reveal problem of public health.
Deaths in a specific class/group registered in a given calendar year
Specific Death Rate = Estimated population as of July 1 in same specified class/group of said year X1000
Example:
No. of death from specific cause registered in a given year
Cause Specific Death Rate = Estimated population as of July 1 of the same year X 1000
No. of deaths in a particular age group registered in a given calendar year
Age Specific Death Rate = Estimated population as of July 1 of the same year X 1000
No. of deaths of a certain sex registered in a given calendar year
Sex Specific Death Rate = Estimated population as of July 1 of the same year X 1000
specific death rate
measures the frequency of occurrence of the phenomenon during a given period of time.
No. of new cases of a particular disease registered during a specified period of time
IR = Estimated population as of July 1 of the same year X 1000
incidence rate
measures the proportion of the population which exhibits a particular disease at a particular time. This can only be determined following a survey of the population concerned, deals with total (new and old) number of cases.
No. of new and old of a certain disease registered a t a given time
PR = Total No. of persons examined at a same given time X1000
prevalence rate
more accurate measure of the risk exposure
No. of person acquiring a disease registered in a given year
AR = No. of exposed to same disease in the same disease in the same year X 1000
attack rate
shows the numerical relationship between deaths from all causes (or groups of causes), age (or group of age) etc. and the total no. of deaths from all causes in all ages taken together
No. of registered deaths from specific cause or age for a given calendar year
PM = No. Of registration deaths from all causes, all ages in same year X1000
proportionate mortality (death ratios)
index of a killinf power of a disease and is influenced by incomplete reporting and poor morbidity data.
No. of registered deaths from a specific disease for a given year
case fatality ratio
