Public Health Week #4

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What is Epidemiology?

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-It is the study of the distribution of health and illness within a population

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The goal of epidemiology is to?

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-To determine the causal factors of health issues in order to improve the health and safety of whole populations
-To understand causality well enough to devise interventions to prevent adverse events before they start.

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Epidemiology & Core Functions:
Assessment

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monitoring and diagnosing health status of the community using data and health indicators

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Epidemiology & Core Functions:
Assurance:

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enforcing laws, linking people to services, evaluating effectiveness of programs.

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Epidemiology & Core Functions:
Policy Development

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informing, educating, mobilizing community efforts, developing plans.

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Define Risk

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the probability that a disease or other unfavorable health condition will develop.

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Define populations at Risk

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collection of people among whom a health problem has the possibility of developing b/c certain influencing factors are present

ex. exposure to HIV, lack of immunizations

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Define Target Group

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individuals that would benefit from a particular intervention for the target group.

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Endemic disease

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Demonstrates a consistent chain of transmission from person to person for 12 months or more in a particular geographical area

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Epidemic

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Occurrence of a great number of cases of a disease, beyond what is normally expected

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Pandemic

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an epidemic that spreads across a large region (for example a continent), or even worldwide.

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Outbreak

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An increased number of cases in the population that does not approach epidemic proportions

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Descriptive epidemiology

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includes investigations that seek to observe and describe patterns of health related conditions that occur naturally in a population.

What is the problem?
Who is affected?
Where were they effected?
When were they effected?

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Analytical epidemiology

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Aims to research and study both the risk factors and protective factors of diseases.

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Experimental epidemiology

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follows and builds on information gathered from descriptive and analytical approaches.
the investigator usually controls or changes the factors suspected of causing the health condition under study, then observes what happens to the health state.

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Analytic epidemiology (3 Types)

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1. Cross-sectional study-a snapshot
2. Case-control study-a comparison of groups
3. Cohort study-a comparison of individuals who have certain characterisitcs in common, free o diseases or health problems at the time of the study.

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Cross-sectional study

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explores a health condition's relation to other variables in a specified population at a specific point in time. Can show that the factor and the problem coexist. Ex. One study compares the incidence of gonorrhea in a 55-block area in urban New Orleans with a "broken window index," which measured housing quality, abandoned cars, graffiti, trash, and public school detioration.

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Case-control study-a

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compares people who have a health or illness condition (# of cases with condition) with those who lack this condition. (controls)

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Cohort study

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study the development of a condition over time. A cohort study begins by selecting a group of people who display certain defined characteristics before the onset of the condition being investigated.

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Epidemiologic Triad

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-Host, Agent, Environment
- the interrealtionship betwwen these three things can enhance or decrease likeleyhood for illness and disease.

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Agent

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can be bacteria, virus, fungus. etc.

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Host

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client that is the client that is effected by the agent.
- look at age, immunity, wellness, lifestyle factors (obesity)

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Environment

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-factors in the physical, biological and social
-climate, plants and animal life, SES factors, working conditions,

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Web of Causation

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another model for understanding the multiple factors that bring about a condition.
-holistic model too.
-It also includes environment, host, and agent factors.
-Maps out direct and indirect factors that contribute to the prevention or development of a disease.
-Beneficial in looking at chronic diseases and environmental effects.
- in the web- 1. behavioral, 2. social, 3. genetic, 4. environmental.

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Determinants of Health

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- HP 2010 uses this model
- holistic and looks at:
a. Social Environment
b. Physical environment
c. Individual biological factors
d. Individual behavioral factor

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Determinants of Health
(what the model includes)

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1. Policies and Interventions
2. Behavior, biology, individual, biology, social environment, physical environment.
3. Access to quality health care

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Epidemiology Process (8)

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1. Define problem
2. Gather Data
3. Describe the problem
4. Formulate a hypothesis
5. Test Hypothesis
6. Plan for control
7. Implement control plan
8. Evaluate control plan

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10 Leading Causes of Death in the U.S.

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1. Heart Disease
2. Cancer
3. Medical errors
4. Strokes/ CV
5. RR disease
6. Accidents
7. Diabetes
8. Alzheimer's
9. Kidney Disease

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Major Trends, what disease are:
1-Eradication?
2-Near eradication?
3-Targeted eradication?

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1-Smallpox
2-Poliomyelitis
3-Rubella, Dracunculiasis

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Major Trends, what disease are:
4-Vaccine Preventable Diseases (6)?

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-Measles/Mumps/Rubella,
-Tetanus/Diptheria/Pertussis,
-Hepatitis A and B,
-Varicella, Influenza,
-Pneumococcal pneumonia

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Major Trends, what diseases with noted fluctuations?

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-Tuberculosis
-Influenza
-Pneumococcal disease

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Major Trends,
1-what are diseases of interest?
2-what are new emerging/ reemerging diseases?

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1- Avian influenza, West Nile virus
2- MRSA, VRE

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Major Trends,
1-what diseases are increased incidence and prevalence?
2-what are decreased incidence and prevalence?

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1-HIV/AIDS
Chlamydia
Rocky Mountain spotted fever

2-Syphilis

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PRIMARY SOURCES OF HEALTH DATA (6)

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1. Reportable Diseases (TB, malaria, viral influenza, SARS)
2. Hospital Discharges
3. Disease Registries (lead exposures, pesticides exposures, birth defects, and cancers)
4. Vital Statistics (birth certificates and death certificates)
5. Census Data
6. Survey Data

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QUALITY OF HEALTH DATA (4)

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1. Timeliness
2. Accuracy
3. Completeness
4. Representativeness- -all healthy events are equally and accurately reported.

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COMMON STATISTICAL MEASUREs:
(2)

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1. Crude number (count)
2. Rate

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Crude number (count)

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the number of cases of a disease or health phenomena or number of a demographic variable in a population or community.
Example, # of deaths, # of females

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Rate

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a measure of the frequency or probability of a health event or phenomena over a specified period of time in a defined population.

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Central tendency

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a single value that is in some way representative of the individual values in the group.

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Mean

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average value of the values in a set.

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Median

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in a set of data the value or point in a series which divides the ranked values into two equal-sized groups, one consisting of values smaller than the median, the other consisting of values larger than the median.

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Mode

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the value in a set of data which occurs most frequently.

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Mode of Transmission

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Means by which the infectious agent or organism that causes a disease is transferred from an infected person or animal to an uninfected one

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Common Modes of Transmission

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Airborne transmission
Fecal–oral transmission
Direct contact
Sexual transmission

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Other common modes of transmission (3)

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Transmission by direct inoculation
Transmission by insect or animal bite
Transmission by other means

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Direct inoculation

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a needle stick

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Airborne Transmission

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-Infectious organism is present in the air and is inhaled by a susceptible host during respiration
a. Exanthems (present as skin rashes, but droplet nuclei that cause it)
b. Infections of mouth and throat
c. Infections of upper and lower respiratory system

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Fecal–Oral Transmission

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-Direct transmission
-Indirect transmission (not washing hands, bad water, etc..)

Examples:
Salmonella
Shigella
Campylobacter

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Direct Contact

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-Skin-to-skin contact
-Direct contact with mucous membrane discharges (sheets)

Examples:
Mononucleosis
Impetigo
Scabies
Lice

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Sexual Transmission

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Sexual contact (direct contact transmission)

Examples
HIV/AIDS
Gonorrhea
Syphilis
Genital herpes
Hepatitis B, C, and D

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Transmission by Direct Inoculation

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-Infectious agent is introduced directly into the bloodstream of the new host
Transplacentally
Contaminated needles or blood products
Splashing of contaminated body fluids

Examples
HIV/AIDS

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Transmission by Insect/Animal Bite

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Mosquito - Malaria
Warm-blooded animals - Rabies
Ticks - Lyme disease and Rocky Mountain spotted fever
Fleas- Plague

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Transmission by Other Means

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Spores in soil

Examples
Tetanus
Hookworm

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Epidemiological Factors: Biophysical

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Age
Gender
-Race/ethnicity
-Physiologic health status
-Immunity

* important during data collection

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Epidemiological Factors: Psychological

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-Effects of stress
-Risk-taking behaviors
-Depression

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Epidemiological Factors: Physical Environmental

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Poor sanitation
Overcrowding
Climates with extreme winds and -Contaminated waters
-Regions with infectious insects or animals

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Epidemiological Factors: Sociocultural

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-Poverty/ Homelessness
-Poor nutrition
-Unemployment
-Cultural beliefs
-Gender socialization

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Epidemiological Factors: Behavioral

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-Diet
-Sexual activity
-Drug use
-Use of mosquito nets
-Swimming in contaminated water

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Epidemiological Factors: Health Systems (barriers)

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-Failure or inability to screen for diseases
-Failure to recognize or diagnose certain diseases
-Attitudes about diseases that can influence care

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Role of Community Health Nurse

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-Assess factors contributing to communicable diseases
-Identify presence and extent of communicable disease
-Plan/implement control strategies
-Evaluate effectiveness of disease interventions
-Conduct epidemiological research
-Administer communicable disease programs

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3 Common Types of Epidemiology

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Descriptive epidemiology
Analytical epidemiology
Experimental epidemiology

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Retrospective studies

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looks backward in time to find a causal relationship. Ex. Looking back a the use of lead in interior paint int he U.S., history shows that even though the particular dangers to chidren were documented in English-language literature as early as 1904, the U.S. lead industry did nothing to discourage the use of lead paint on interior walls and woodwork.

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Prospective studies -

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looks forward in time to find a causal relationship to ensure that the presumed causal factor actually precedes the onset of the health problem. Ex. The U.S. Nurses Health Study provided an opportunity for a prospective analysis of the association between night shift work and sleep deprivation and the riks of developing Parkinson disease. In a sample of 85,000 registered nurses, those with 15 or more years of niht shift work had a 50% lower risk of developoing the disease than those nurses who never worked the night shift. Studies such as these provide a mechanisms to evaluate a variety of factors that precede the development of disease and then assess issues of association and ultimately causation.

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Morbidity Rate:

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he relative incidence of disease in a population, the ratio of the number of sick individuals to the total population

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Mortality Rate:

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The relative death rate, or the sum of deaths in a given population at a given time

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*Significance in Identifying Populations at risk

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* It is important when reviewing rates that you understand which measures are being compared (ex. what is considered the total population?)


* These rates are important in making comparisons between populations because they use a common base population to compare between. Instead of comparing percentages from one city to another, with these rates you can compare per 100,000 people and it is more meaningful.


* The population base can vary from 100 to 100,000 people.


* These rates allow identification of occurrence of any health-related condition

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HOST

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* the human who harbors the disease causing agent
* the host's susceptibility is influenced by age, gender, environment, and immunity, lifestyle factors
* some people have the ability to resist pathogens = inherent resistance
* resistance is promoted through preventative interventions

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AGENT

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* the factor that causes the health problem
* can be biologic, chemical, nutrient, physical, and psychological
o bio = ex: bacteria, protozoa, virus, fungi
o chem = in the form of liquids, solids, gas, dust, or fumes. ex: poisonous sprays for pests
o nutrients = ex: too much vitamin A can be toxic
o physical = anything mechanical (chainsaw, automobile) Material (rockslide), atmospheric (UV rays), geologic (earthquake) or genetically transmitted
o psychological =anything that produces stress leading to health problems

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ENVIRONMENT

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* external factors surrounding the host that might influence vulnerability or resistance
* includes: climate, safety of buildings, water and food, geography, animals, plants, insects, microorganisms present, SES, cultural health practices, poverty, working conditions, access to health care, etc

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Web of Causation

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* Maps out the relationships of the direct and indirect factors that contribute to the prevention or development of a disease
* also includes epi triad factors, but includes, behavioral, environmental, social, and genetic

* recognition of multiple causes provides many points of intervention for prevention, health promotion, and treatment
* beneficial for looking at chronic diseases and environmental effects

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Chain of causation

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Reservoir > portal of exit > mode of transmission > agent > portal of entry > host

- Environment can have profound influence at almost any point along the chain

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Web of causation

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Shift in thinking from linear causation to idea that combination of multiple factors was the deciding factor in development of poor outcomes.

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Epidemiology of Wellness

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Movement from concentrating on illness to examining host, agent, and environment in the study of wellness.

A) Characteristics

1) helps to examine, uncover, and focus on new health promotion practices

2) focus wellness on primary prevention level

3) looking at population’s health holistically by looking at:

a) physical, social, psychological environment

b) lifestyle w/ self created risks

c) human biology & genetics

d) system of health care organization

4) Develop policy and research to promote health of populations.

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Alexander Yersin did what?

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with the help of Kitasato's work, was able to discover the bacillus (Yersinia pestis) that was causing the bubonic plague.

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Paul-Louis Simond did what ?

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Was able to trace the bacillus life cycle from rats, to fleas, to humans....the bite of the yersinia flea cuased the plague in humans.

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Eras of epidemiology

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1. sanitary statistics: 1800-1850, miasma, Nightingale, Snow, sanitary conditions
2. infectious disease: 1850-1950, germ theory, microscopes, vaccines, antibiotics
3. chronic disease: 1950 -2000, exposure, risk ratio, control risk factors, lifestyle, agent, environment
4. eco-epidemiology: emerging, global health patterns, geocoding, biomedical technology, information.

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Hill's nine criteria fro evaluating the relationship btwn environmental exposure and potential health outcomes

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1. strength of association
2. consistency
3. specificity
4. temporality
5. biological gradient
6. plausibility
7. coherence of explanation
8. experiment
9. analogy

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natural history

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refers to events that occur before its development, during its course, and during its conclusion.

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natural history's 4 stages of disease

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1. susceptablity- before exposure when host and evironmental factors play a role in one's vulnerabilty.
2. subclinical disease- incubation period, exposure
3. clinical disease- signs and symptoms develop
4. resolution- recovery, disability, or death.

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The primary considerations for descriptive epidemiology are

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frequency and pattern. Frequency evaluates the rate of occurrence, and pattern helps analytical epidemiologists suggest risk factors. Descriptive epidemiology evaluates frequency and pattern by examining the person, place, and time in relationship to health events.
examines factors like age, education, socioeconomic status, availability of health services, race, and gender.
time is important too!

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Relative risk ratio

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Incidence in exposed group/Incidence in unexposed group

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7. Disseminate the Findings

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# esearch should be shared to increase the knowledge base for improved practice and promote future research.
# Choose a specific venue to publish your article to reach the target audience so that you increase your chances of your article being read by those practicing in the community.

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6. Develop Conclusions and Applications

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# Stating conclusions is an outcome of analysis and interpretation
# Make the information useful to other health care workers
# Important to describe mistakes made and lessons learned about study design and other aspects of research.

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5. Analyze the Findings

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# Data is compiled and summarized in graphs and tables.
# Data is analyzed and used to address the original question or test the original hypothesis.
# Accept or reject the null hypothesis
# Summarized data can also generate more questions or indicate areas that warrant further investigation.

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4. Collect the Data

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# The tool to collect data (survey) should be assessed for both face and content validity by experts in the field
# Next step is to pilot test the survey tool on a population similar to the target population. Pilot study is good for determining clarity and relevance of questions. May discover that certain questions were omitted.
# Review from the HUman Subjects Committee before final survey sent out
# Can include a small incentve gift to increase response rate
# In CHN, data collection often can occur as part of an ongoing practice unless the study has been carefully designed.

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3. Design the Study

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# The first step in designing the study is to formulate specific questions to answer or hypothesis to test.
# Sometimes the questions emerge from the lit review or from the researcher's own analysis
# The next step is to plan what study type:

* Descriptive
* Analytical
* Experimental
* Combination
# How will the data be collected?

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2. Review the Literature

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* Before rushing to take action, first review solutions that have been tried previously.
* If many studies have been done on the problem, this information gathered can narrow the study to areas that have not been studied yet or allow researchers to replicate studies to confirm findings in a different setting.
* A lit review article is useful in summarizing all the research that has been conducted on a subject.


Ex: The nurse researcher finds out from previous studies that there is varied levels of receipt of lead poisoning prevention education among parents from 30-60%.

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1. Identify the Problem

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Ex: A nurse researcher is concerned with the lead-poisoning prevention education among parents of young children.