Epidemiology Flashcards
What is an epidemic?
Widespread rampant outbreak of a disease
The flu is an example of an:
a. Epidemic
b. Pandemic
c. Endemic
Epidemic
What is a endemic?
A disease that is typically present within a particular region
What is a pandemic?
An epidemic that is widespread throughout the world.
Who is the father of epidemiology?
John Snow
What did John Snow discover?
He noted that homes that were seved by specific water companies has a higher rate of cholera. He postulated that cholera was spread by polluted water.
What was the result of John Snow’s observation?
The implementation of an experiment that observed two groups. Each group was served by a different water company.
- S&V Company
- L Company
What was the population of the John Snow Cholera experiment?
Homes of people that died from cholera
What were the two variables of the John Snow experiment?
Water company vs. Death Toll
What was the pattern discovered in the John Snow experiment?
Rate of death from cholera was 8.5 times higher in the homes of S&V Water Co.
What technique does the government use to monitor notifiable diseases when they occur?
Epidemiological surveillance
What is the purpose of epidemiological surveillance?
To monitor notifiable disease and prevent the disease from spreading by taking early action.
What are some examples of diseases that must be notified to state and federal agencies?
Syphillis, Tb, Measels, Hepatitis, HIV
What is Hepatitis A caused by?
A virus, carried in contaminated food or water.
What signals an outbreak of hepatitis A?
A rise in the rate of occurence.
What are four factors that must be noted when investigating an outbreak?
Who has the disease,
when was it contracted,
where was it contracted and at
what rate is the disease being contracted.
What is the most difficult factor to ascertain when investigating an outbreak?
Where the exposure occurred. Where was the common source?
T/F: A person that is symptomatic and hospitalized is a worse threat to the population than a asymptomatic person that continues to work.
False
What are the 4 factors/questions you must ask when considering an outbreak?
Who
What
Where
Rate - Does it continue to spread or did it stop spreading?
What disease are investigated even with only one occurence?
Measles, Meningitis, Mad Cow (encephalitis), Polio, Plague, Diptheria, Cholera
What are the symptoms of Legionaire’s Disease?
Fever, muscle aches, pneumonia
When did the 1st identifiable outbreak of “Legionaire’s disease” occur?
[Not really the 1st outbreak]
In 1976, at The American Legion Conference in Philadelphia
What pattern did the CDC notice when investigating Legionaire’s disease?
The CDC noted that most deaths occurred in those staying in a specific hotel, while some were near the hotel.
What was the source of the spread of Legionaire’s Disease
A water cooling tower that was used for air conditioning was contaminated with bacteria.
What was the transmission of Legionaire’s Disease? How was the determination of the transmission concluded?
The transmission seemed to be airborne, not person-to-person, since family members were not infected.
Where there other documented occurrences of Legionaire’s disease prior to identifying the disease?
Yes! The bacteria was found in preserved blood and tissue from 1965 from 80 pneumonia patients who died from unexplained cause.
What study investigated the factors that contribute to heart disease?
Framingham Study
According to the Framingham study, what era was heart disese more prevalent?
After WWII
1 in 5 men were affected by heart disease by the age of 60.
What risk factors did the Framingham study identify?
BP, Elevated cholesterol levels and smoking
What was the effect of the Framingham study?
New standards were established regarding BP
What were the former beliefs about BP prior to the Framingham study?
Previously it was believed that BP normally increased with age and that higher levels were acceptable with increase in age.
What conditions are associated with elevated BP?
Weight gain & Lack of Exercise
What condition is associated with increase heart disease?
High cholesterol
What were the long term effects of the Framingham Study?
Decrease in death rates from heart disease with a decrease in associated factors: BP was lowered, decreased cholesterol levels and a decrease in smoking occurred.
What were the vairables studied in the Doctor’s Lung Study?
Tobacco smoking vs. Lung cancer
What was the duration of the Doctors Lung Study?
4 years
Who were the subjects in the Doctor lung study: The doctor’s themselves or their patients?
The doctors
What was determined in the Doctors Lung Study?
The death rate from Lung Cancer was 20x higher in smokers than non smokers, increasing as the amt of smoking increased
What result did the publishing of the Doctor Lung study have on death rate?
The death rate of ex-smokers was lower that that of smokers, with a decline as the time of nonsmokers increased.
[The longer you quit smoking the longer you were likely to live.]
Is death rate between smokers vs. non smokers affected by living environment?
The contrast in death rates between smokers and non smokers was consistent whether they lived in urban or rural areas.
At what age were death rates from heart attacks significantly higher amongst heavy smokers?
35-54
What kind of study is the Framingham Study (and Lung Cancer #2 study of the Epidemiology packet)?
Prospective cohort study
What are the beneficial characteristics of cohort studies?
Large number of people studied over an extended period of time
Most reliable for causes of chronic disease
What is epidemiology?
The study of the DISTRIBUTION and DETERMINANTS of DISEASE FREQUENCY in HUMAN POPULATION
What must be clearly identified so that each case can be counted in epidemiological studies?
A disease
The definition of _______ is a crucial part of an epidemiological investigation
Disease
What is the best marker to determine if a patient has Hepatitis A?
A Blood test
Nausea, weakness and diarrhea are classified as what kinds of symptoms?
Non specific symptoms
What are the two factors that are the focus of epidemiology?
Disease and health outcomes
T/F: Studying traffic accident injuries to prevent detrimental outcomes is considered an epidemiological study?
True
What is frequency?
Number of cases
What is rate?
The number of cases and the relationship of that number to the size of the population
(# of cases developed within a population at risk)
When determining rate what is the denominator ?
Population at risk
In determining the rate of ovarian cancer, what would the population consist of?
Only women of a certain age
What is incidence?
The rate of new cases of a disease in a defined population over a defined period of time
What statistic is useful in identifying the cause of a disease?
Incidence rate
The introduction of thaliomide caused birth defects to rise in Europe in 1960. This is an increase in what?
Incidence rate
What is prevalence?
The total number of cases in a defined population at a single point in time
How is prevalence measured?
With a survey
What is the difference between prevalence and incidence?
Prevalence and incidence are related to each other, but it depends on how long people live with the disease.
If you don’t die from a disease and you live with it for a long time which rate is higher?
a. Prevalence
b. Incidence
Prevalence
If people die from a disease quickly which rate is higher?
a. Prevalence
b. Incidence
Incidence
What are two types of fatal incidence rates?
death rates/mortality rates
What are death rates and mortality rates used as a measure of frequency for?
For diseases that are fatal
When are death rates close to incidence rates?
For the most lethal diseases
Does breast cancer has a lower mortality rate or incidence rate?
Mortality rate (many women that get breast cancer survive)
The “who, where and when” of a disease reflects the __________ of the disease.
Distribution
The following is which component of the distribution of a disease:
- Characteristics of the victims of the disease; age; sex; race and economic states
WHO
The following is which component of the distribution of a disease:
Compares disease frequency in different geographic divisions- countries, states, urban/rural
WHERE
The following is which component of the distribution of a disease:
Trends in disease frequency over time. Noting if the disease is increasing, decreasing, stabilizing, or if there are seasonal patterns?
WHEN
Information of the ___________ of the disease leads to clues as to the ____________ of disease
Word Box:
- Distribution,
- Determinants,
- Causes,
- Effects,
- Epidemiology,
- Spread,
- Location
Distribution … Determinants
Cancer of the colon is more common in industrialized countries. Is this due to genetic factors or diet?
Diet
Why is the prevalence of breast cancer believed to be related to diet?
International rates are similar to those of colorectal cancer, which is related to diet
Relevance of who and when are not proof of a cause of a disease but help us form _________ about the disease
Associations
What are statistical methods used to determine when analyzing an experiment?
If the differences are significant. It must be proven that the results could not have occurred by chance alone
What type of study is conducted to evaluate a new treatment?
An Intervention Study
What type of intervention study is the response of the treated group compared to that of the control group?
Clinical trial
What are the criteria of the treatment in a clinical trial?
The treatment must not be harmful and its effectiveness must be in question in order to withhold it from the control group
What is an inactive sustance similar in appearance to the drug being tested called?
A placebo
About 30% of people receiving placebos report improvement or side effects similar to the medication being tested. What kind of effect is this?
Placebo effect
What is the most convincing type of clinical trial?
A randomized, double blind study.
What does double blind mean?
What does it prevent?
Neither the subjects nor the experimenters know which group the subject is assigned to.
This prevents bias
Jonah Salk developed a paralytic polio vaccine. What was the effect of the vaccine on the incidence rate of polio in the treatment group?
The vaccine lowered the incidence rate of polio.
Who developed an oral vaccine for paralytic polio?
Albert Sabin
What was the purpose of the Physician’s Health study?
To determine if aspirin reduces mortality from heart disease and does beta carotene reduce the incidence of cancer
Why was the aspirin portion group of the physician’s health study trial halted early?
The aspirin treated group had a significantly reduced chance of a heart attack
T/F: Subjects in a cohort study are not healthy at the beginning of the study.
False
All are healthy at the beginning
What does a cohort study determine?
It is an analysis of risk factors and follows a group of people who do not have the disease, and uses correlations to determine the absolute risk of subject contraction.
The purpose of a cohort study is to determine the chances that you will get the disease being studied based on whether or not you are exposed to specific risk factors.
What do epidemiologic studies attempt to reveal?
Association between exposure and the disease in question.
Do epidemiological studies prove causation?
No
What is the measure of the strength of association in cohort studies
relative risk
What is the defintion of relative risk
Ratio of the incidence rate of the exposed group compared to those not exposed
What does a relative risk of 1.0 mean?
Means that there is no association between exposure and the disease
What does a relative risk of >1.0 mean
there is an increased risk in the exposed group
What does a relative risk of <1.0 mean?
there is a decreased risk in the exposed group
How do you calculate the relative risk?
Expose group / unexposed group = relative risk
What do case control studies evaluate
Evaluates people who are already ill and looks back to determine their exposure (retroactive)
What are the criteria for case control studies in comparision to cohort studies?
Case control studies are done on a smaller number of people and requires less time than cohort studies.
In a case control study, people with the disease are called…
cases
In a case control study, people without the disease matched for age, sex and other factors that might be relevant to the disease are called…
controls
What did the case control study regarding Reye’s Syndrome try to determine
If respiratory or gastro-intestinal infection or chickenpox were correlated with Reye’s Syndrome
how is the odds ratio calculated
estimation of the strength of association between the exposure and the disease
If a case control study had been done, what is an estimation of the relative risk?
Odds Ratio
What did the Odds ratio reveal in subjects that took oral contraceptives vs. subjectives that did not?
Subjects that took oral contraceptives for more than 4 years had double the risk of developing breast cancer as compared with those that did not use oral contraceptives.
(many weaknesses of this study)
