Lecture 9 - Epidemiology Flashcards
Who as a pioneer in public health in the early 20th century?
Charles-Edward A. Winslow
What did Charles-Edward A. Winslow say about epidemiology?
He called epidemiology the “diagnostic discipline” of public health
Epidemiological methods are used to:
- Investigate the cause of diseases
- Identify trends in disease occurrence
- Evaluate the effectiveness of interventions
What does it mean to assess risk factors?
Find out what is causing the disease/public health concern
Under “assessment” there are 3 categories -
Risk factors
Trends
Source
What does it mean to assess trends?
To find out if there’s some demographic or activity that is more likely to result in the disease/problem. Is there a certain time period when this is likely to occur?
What does it mean to asses the “source”
Typically refers to an infectious disease, but it could also be a chemical contaminant.
Water/food source is the most common
What does endemic mean?
The baseline/ expected levels of a disease/public health concern
Almost all diseases or concerns have a minimum expected level. What is the exception to this
Diseases that already have vaccines - they do not have expected minimal levels so even one case could be considered an epidemic
What is an epidemic?
An increase in the normal expected values
Sometimes, there’s only certain people (A WHO) you see an increase in, and other times its certain time periods (WHEN) (ex the flu)
Other times there are certain regions/workplaces where in increase is seen (WHERE)
Of the who, when, and where of an epidemic, which is the hardest to track down?
The WHERE
Epidemiology is derived from the word _____
Epidemic
Epidemiology is heavily used to perform….
The ASSESSMENT function of public health associated with identifying RISK FACTORS
Epidemiologists study the pattern of ______ occurrence in human population as well as the….
Epidemiologists study the pattern of disease occurrence in human populations as well as the factors that influence these patterns
The expected rate of a disease is called the ____ rate
Endemic
Accidents are _____ in workplaces and are therefore….
Accidents are ENDEMIC in workplaces and are therefore expected at a LOW RATE
When accidents/injuries in a workplace happen with more frequency than they should, what exists?
An EPIDEMIC that needs to be investigated to prevent this high rate of accidents/injuries
When signs of an epidemic are detected, what 2 things to epidemiologists do?
They ask questions and collect data to learn about the disease and how it spreads
What 3 questions do epidemiologists ask
WHO is getting the disease
WHEN is the disease occurring
WHERE is the disease occurring
When epidemiologists collect data and gain knowledge about the disease, what is their ultimate goal of what to do with this knowledge?
They want to control and minimize the occurrence of the disease
What is an early example of the use of epidemiology to study and control a disease?
London in 1853/1854
John Snow was concerned about the cholera epidemic so he collected info from his patients to determine WHY cholera was happening at a high rate. He determined that the death rates in parts of London that used a common water supply were the highest. Lambeth company changed its source of water to an area of the Thames river that was free of pollution.
Hypothesized that the outbreak was due to polluted drinking water - did a study which showed the Southwark company was responsible
What is “epidemiological surveillance?”
A system requiring notable diseases to be reported as soon as they’re diagnosed so that an epidemic is recognized before people starts dying
Where are generally “notifiable” diseases?
Usually infectious diseases whose spread can be prevented if appropriate action is taken
Name some examples of notifiable infectious diseases
Tuberculosis, hepatitis, measles, syphilus
What is the primary reporting agency for tracking epidemics?
The CDC
Besides infectious disease, what are some other things that are required to be reported?
Birth defects, cancer, and other non infectious diseases
Physicians, hospitals, and clinical laboratories must report any cases of “notifiable diseases” to whom?
Their local health department, which reports to the state health department, which reports to the CDC
Why are birth defects and cancers required to be reported?
To help identify potential environmental causes that could be controlled or eliminated
What are some examples of NONINFECTIOUS notifiable diseases?
-cancer clusters
-carbon monoxide poisoning
-lead, elevated blood levels
-foodborne disease outbreaks
-waterborne disease outbreaks
-pesticide related illness or injury (occupational and nonoccupational)
how many infectious notifiable diseases are there?
66
What is the only infectious disease that requires reporting in BOTH humans and animals?
rabies
are most infectious diseases notifiable?
yes
was coronavirus a notifiable disease?
no
what infectious disease is classified as a notifiable disease in ALL 50 STATES?
hepatitis A
Hepatitis A is caused by…
a virus that can contaminate food and water
Is hepatitis A fatal?
no-not to healthy people
but it can make people sick for several weeks and require hospitalization
What signifies an epidemic?
a sudden increase in the number of cases
an epidemic calls for…..
an epidemiological investigation to determine the reason why it’s occurring
the epidemiological investigation requires asking what 3 questions?
WHO is being affected?
WHERE is the disease occurring?
WHEN did people become infected?
in the case of a hepatitis A outbreak, how would the investigator go about answering the 3 questions?
starts at the WHO is being affected - the reported cases
each person with hepatitis must be interviewed and asked WHEN (the date) the first symptoms appeared
What is the incubation period of Hepatitis A? What does this mean?
30 days - it takes around 30 days for symptoms to appear after being exposed to hepatitis A. this means it is possible to work back to an estimated date of “when” they were exposed
In the case of an outbreak of Hepatitis A, what question is the hardest? Why?
the WHERE question.
where did they affected people obtain their food/water?
health department might have to close a restaurant for instance until the affected chef is declared healthy
The “where” question is all about…
SHUTTING DOWN THE SOURCE
In the case of a Hepatitis A outbreak, whose task is it normally to do these investigations?
epidemiologists at local health departments
a large number of epidemiological investigations such as the Hepatitis A outbreak deal with…
food poisoning outbreaks caused by contamination with SALMONELLA or SHIGELLA
Salmonella and Shigella both cause…
notifiable diseases
Can a single case of an eradicated disease trigger an epidemiological investigation?
YES
What is an example of a disease that has been eradicated by vaccine and is highly contagious?
the measels
What happened with the measles in the late 80’s? What was the conclusion of this?
a number of measles epidemics occurred between 1989-1991 on college campuses. Concluded that most of the affected students had been immunized as infants, so a SECOND VACCINE FOR TEENS WAS NECESSARY to ensure complete coverage for the rest of their lives
Legionella bacteria are responsible for a number of outbreaks of _______ across the country
pneumonia
Although infectious agents are usually suspected at first, what else must epidemiologists consider?
exposure to toxic substances
What puzzling case showed that exposure to toxic substances must be considered too - not just infectious agents?
new mexico in 1989 - L-tryptophan case
(EMS epidemic of 1989)
What is similar to the EMS epidemic of 1989?
toxic oil syndrome
both were tracking manufacturing problems
government intervention to remove the contaminated products put an end to both epidemics
________ is a major line of defense in protecting the public against the disease. It is a warning system that alerts the community that something is wrong
EPIDEMIOLOGIC SURVEILLANCE
What are some diseases of aging?
cancer and heart disease
Epidemiology can also investigate…..
the causes of diseases common in older age (cancer, heart disease)
Do cancer and heart disease have a single cause?
NO- tend to develop over a period of time and are chronic and disabling rather than rapidly fatal
Under epidemiology, how are age related disorders handled?
PREVENTION - can’t magically be cured by a drug or a vaccine
they are managed by TREATEMENTS but can still reoccur
the hope is that we can minimize these illnesses or at least delay their onset
PREVENTION requires understanding which 2 things?
-the cause of the disease
-the factors that influence disease progression
which are more complicated - epidemiological studies of acute outbreaks or chronic illnesses?
CHRONIC ILLNESSES
What are 4 exceptions - cases in which chronic illness was EASY to identify?
-clear link of smoking to lung cancer
-clear link of HIV infection to cervical cancer
-clear link of overexposure of sunlight to skin cancer
-clear link between obesity and type 2 diabetes
what is the term for different factors that play a part in causing a disease?
risk factors
why is it so difficult to determine the causative factors of chronic diseases?
the long period over which these diseases develop
What is the leading cause of death in the United States for both men and women?
heart disease
What decade did mortality from infectious disease begin to decline and heart disease began taking its toll?
around the 1920’s
after ww2, ___ out of every ____ men was affected with heart disease before the age of ____ and little was known about why
after ww2, ONE out of every FIVE men was infected with heart disease before the age of 60 and little was known about why
WHERE and in WHAT YEAR was an epidemiological study conducted to investigate what factors might be causing heart disease?
MS in 1948
What was significant about the Framingham, MS epidemiologic study?
it was the 1st major epidemiologic study of a chronic disease
What kind of people did the Framingham study look at? What factors were they evaluated for?
over 5000 healthy, middle aged people were examined on their WEIGHT, BLOOD PRESSURE SMOKING HABITS, AND OTHER BLOOD TESTS.
The same studies were conducted every 2 years for the rest of their lives
The framingham study identified that there were THREEE MAJOR RISK FACTORS of heart disease. What are they?
-high blood pressure
-cholesterol
-smoking
doctors used to believe what about blood pressure?
that blood pressure naturally increased as people aged and it was perfectly normal and healthy
what 2 habits increase the chance of elevated blood pressure and cholesterol values? (overall - increase in risk of heart disease)
weight gain and lack of exercise
after the framingham studies, death rates from heart disease have significantly ______
fallen
What is HDL cholesterol? How was we increase our levels?
the “good cholesterol”
we can increase by drinking alcohol in moderation and exercising
What were the 2 prime suspects in the dramatic increase in cancer in the past?
-tobacco smoking
-air pollution
What was Doll and Hill’s survey?
(early 50’s)
2 british epidemiologists sent a questionairre to alll physicians in the UK asking if they were current smokers, past smokers, or ex smokers
over 40,000 doctors responded
concluded:
-death rate from lung cancer was about 20 times higher among smokers than nonsmokers
-death rate among ex smokers was lower than that of smokers and declined as the length of time increased since the dr had quit smoking
-lung cancer mortality between smokers and nonsmokers was the same whether the dr’s lived in rural or urban areas (not air pollution)
-deaths from heart attack were higher in heavy smokers than nonsmokers
1/3 of the dr’s surveyed had died after 20 years
What study was similar to the Doll and Hill survey?
Tha Hammond and horn study
What did the Hammond and Hill study conclude?
-Cigarette smokers were 10x as likely to die from lung cancer than nonsmokers
-heavy smokers were 2.4times as more likely to die of heart disease than nonsmokers
The Framingham study and the 2 lung cancer studies are examples of what kind of study??
Prospective cohort studies
What are prospective cohort studies?
They follow large numbers of people over extended periods of time who are PROSPECTIVE (don’t yet have the disease)
