N251 exam 4: lecture 6

epidemiology

The study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems.

-deals with natural history of dieases

lost cast: very diverse cast of characters from very different people with backgrounds- makes professor think of collecting evidence from people
-trying to learn about disease in population and how theyve spread

the importance

Health care and planning

tool for investigation of the cause of disease
-defining disease characteristics, such as prevalence, incidence, and mortality

role of epidemiologists

1. trace the spread of disease in a population
-to identify its origin
-mode of transmission
2. with the help of data obtained from
-clinical studies
-disease reporting surveys
-insurance questionaires
-interviews with patients
this will help him define common factors that constitute a disease

scientific method

A series of steps followed to solve problems including collecting data, formulating a hypothesis, testing the hypothesis, and stating conclusions.

1. ask a question
2. do background research
3. construct hypothesis
4. test with an experiment
5. analyze results
6. hypothesize is true REPORT
-if not construct a new one

outbreak intestigation steps

1. prepare for field work
2. establish the existence of an outbreak, consider the severity, potential for spread, public concern and availability of resources
3. verify the diagnosis
4. define and identify the cases
5. describe and orient the data in terms of time, place, and person
6. develop hypothesis
7. evaluate hypothesis
8. refine and carry out
9. implement control and prevention measures
10. communicate findings

disease surveillance

Ongoing systematic collection, analysis, interpretation, and dissemination of specific health data for use in public health.

data collected in a surveillance system can be used for many purposes
-to estimate the magnitude of health problem
-to understand the natural history of a disease
-to detect outbreaks or epidemics
-to document the distribution of health event
-to test hypothesis about causes of disease
-to monitor changes in infectious organisms

frequency and distribution based classifications

1. sporadic: occasional cases occurring at irregular intervals
2. endemic: persistant occurrence with a low to moderate level
3. hyper endemic: persistently high level of occurrence
4. epidemic: occurrence clearly in excess of the expected level for a given time period
5. pandemic: epidemic spread over several countries or continents, affecting a large number of people

sporadic level

occasional cases occurring at irregular intervals

-cyclosporiasis in the united states
-not all the time everywhere

endemic level

persistent occurrence with a low to moderate level
-something always going on in background

-common cold

epidemic level

occurrence clearly in excess of the expected level for a given time period
-beginning and an end

hyper endemic

persistent, high levels of disease occurrence

-mosquito borne diseases
-west nile

pandemic

epidemic spread over several country or continents affecting a large number of people

-covid, H1n1

Major uses of Epidemiological Research

assessing the communities health

making individual decisions: making info available on risk factors

Scope of epidemiology

1. Disease definition: characteristics or combination of character that best discriminate disease from non diseased
2. disease occurence: the rate of development of new case in population. The proportion of current disease within population.
3. disease causation: the risk factors for disease development and their relative strength with respect to an individual and population
4. disease outcome: the outcome following disease onset and of the risk factors
5. disease management: the relative effectiveness of proposed therapeutic interventions
6. disease prevention: the relative effectiveness of proposed preventive strategies including screening

epidemiologic triangle

agent, host, environment

-used for describing the causality of infectious diseases
-provides a framework for organizing the causality of other types of environmental problems

Host

-age, sex, race, previous diseases matter and ability to deal with agent that is infecting
-can be biological ,chemical: smoke, physical: trauma, radiation, nutritional

Enviornment

where host and agent exist

Father of Epidemiology

John Snow
-he noticed people with cholera developed immediate digestive problems
-cramps, vomiting, diarrhea
-face, feet, hands, shriveled and turned blue
-died in less than a day
-probably spread by vomiting and diarrhea
-he thought the disease was being spread through a contaminated water source but no one believed him

what he did:
-tracking deaths
-people had pumps for water in the city
-he believed was the cause of cholera outbreak
-he tried to get pump shut down but was not successful initially - once was shut down the outbreak went down
-was shut down late at end of epidemic
-discovered sewege leak years later

clinical vs epidemiology

clinical:
-individual
-lab tools for diagnosis
-does not take others into account
-no assumptions
-doesnt help public policy


epidemiology:
-focus on group
-takes all factor into account
-assumptions
-does help public policy

BOTH
-collect and use data
-take action

uses in public health practice

-investigation of epidemic
-surveillance for diseases
-make projections
-assess the programme for mass screening for diseases
-assist in formulating medical teaching curriculum

example of bioterrorism in US

during the 80s
-with the guru in Oregon
-set up his collective in oregon and he was trying to seize control of political power
-trying to get a slate of people selected
-to do this: trying to control election
-goal was to keep people from going out to vote
-few days before the election, followers of his went to salad bars and buffets and spread salmonella
-didnt work quite as well as they planned and plot was discovered and traced back to them

common source outbreak

an outbreak characterized by exposure to a common, harmful substance

intermittent: factory releases chemical that isnt released all the time

continuous

point source outbreak

a common source outbreak in which the exposure period is relatively brief so that all cases occur within one incubation period.

-good with a bacteria or a virus

propogated outbreak

Outbreak of a disease transmitted person to person, with successive "waves" of cases identified, each one greater than the one before

-may last longer than common source epidemics
-covid is good example