Epidemiology 1 Flashcards
What does epi mean?
on the top/on/above
What does demos mean?
people / citizens
What does logia mean?
knowledge/writing/words/study
What does epidemiology mean?
The study of what is upon the people.
Who studied cholera?
John Snow
When did john snow study cholera?
1846 - 1860
What was cholera originally believed to result from?
Believed to result from
“miasma” (odors/gas/vapors from
decomposing animals/humans)
How did John Snow stop spread of cholera in London Soho?
Removed pump handles of water pumps so no contaminated water could be drawn from underground.
How does someone get cholera?
Drinking or eating food or water contaminated with the bacteria.
what bacteria causes cholera?
vibrio cholerae.
Why was the water underground contaminated?
Lack of sanitation, inadequate water treatment.
What does cholera do to intestines?
Induces loss of fluids in intestine(s)
Is cholera gram neg or gram pos?
Gram negative
Why does cholera cause people to lose alot of water?
Diarrhoea
What does diarrhoea cause?
Dehydration.
At the time of John Snow how was cholera treated?
At the time of John Snow, there was no treatments.
How is cholera treated today?
Today, we have antibiotics such as doxycycline and water filtration systems. We also have sanitations, hygiene, and vaccination.
What are the three questions asked in epidemiology?
1- Location
2- Who
3- When
What happened in Philadelphia 1976?
National convention of the american legion.
What do we look at in epidemiology?
- Creating solutions to problems
- Surveillance
- Risk factors
- Interventions and implementation
This is public health.
What happens in a case control study?
A specific group of patients is examined (infected) and is compared
with another group of patients that are called “controls” (non-infected)
What are the case group?
Infected
What are the control group?
non-infected
What is an Odds Ratio used to do?
to assess how likely a patient will develop a disease/condition.
What does it mean if OR > 1 ?
patients that have been exposed are more likely to develop the disease/condition
What does it mean if OR = 1 ?
no association between exposure and disease/condition
What does it mean if OR < 1 ?
patients that have been exposed are more likely to be protected against the disease/condition
Pros of case control studies?
Fast
Cost effective (cheap)
Cons of case control studies?
Bias
Appropriate controls
What is a cohort study?
A cohort (group of patients) is followed over time.
Initially, patients are healthy
What is the aim of a cohort study?
Aim = determine factors causing a disease/condition
What is a Relative risk used to do?
This is a way to assess the probability to develop a disease/condition
What is RR?
relative risk
What is OR?
Odds ratio.
Whats it mean if RR > 1 ?
patients that have been exposed are more likely to develop the disease/condition
Whats it mean if RR = 1 ?
no association between exposure and disease/condition
Whats it mean if RR < 1 ?
patients that have been exposed are more likely to be protected against the disease/condition
Pros of cohort studies?
True estimations
Patients are followed longitudinally
Cons of cohort study?
Slow
Expensive
What does a descriptive study involve?
1- Case report
Focusing on a single patient (n=1)
eg: a rare disease observed in a patient
2- Case series
Focusing on a few patient
eg: a condition observed in several patients (n~30)
How are health problems solved?
Step 1 = Data collection
Step 2 = Assessment
Step 3 = Hypothesis testing
Step 4 = Action
Afterwards,
Step 1 = Surveillance
Step 2 = Inference
Step 3 = Determine how and why
Step 4 = Intervention
What does it mean if there is no agent?
No agent = genetics?
Eg – dementia, MS, autoimmune diseases.
What can epidemiology be performed on?
Epidemiology can be performed on communicable or non-communicable disease(s)
Define epidemic?
An epidemic is the consequences of an outbreak of diseases, usually caused by agents
exception : obesity (for example)
What does an outbreak involve?
An outbreak involves a cluster
Why can tractors kill people in georgia usa?
Lack of experience
Lack of awarness
Lack of strength
Hills causing tractors to roll back and run people over, especially in the north.
What is incidence proportion also known as?
also called “cumulative incidence
What is Incidence rate also known as?
also called “incidence density rate”
and “person-time incidence rate”
Why more adults obese than kids?
Metabolism slows - harder to keep at a healthy weight.
Unhealthy eating habits
Less exercise / sedentary life style.
Why might more boys be obese than girls?
Girls may have healthier diets. (eg, girls = veg, boys = fried food)
Men eat more since men have bigger bodies on average.
Maybe girls exercise more than men do.
What is the course of action to avoid an epidemic?
1- Continuous monitoring
2- Early detection
3- Efficient containment
4- Prevention
What does continuous monitoring consist of?
- Registry of infectious diseases
—HIV, ZEBV, TB - Trend analysis
—constant, exponential, sigmoid, logarithmic
What does early detection consist of?
- Diagnostic, tests, laboratories
—PCR, ELISA
What does efficient containment consist of?
- Isolation, lockdown
- Treatment
—Antibiotics (bacteria)
What does prevention consist of?
- Vaccination, education, public policies
- Research
—Clinical trials
What are ALSO attack rates?
% ill
Why are older people more prone to illness and more likely become infected and ill?
Weaker immune systems
What cause of action do you take after examining/observing a disease?
Hypothesis
What would a hypothesis of a disease include?
Why?
Disease caused by what/who ?
Is the disease transmissible?
How was legionnaires’ disease HYPOTHESISED to be transmitted?
“Investigation of the mode of transmission included the following general categories:
person to person,
food,
tobacco,
alcohol,
water,
animals,
ice,
fomites,
and air.”
What are fomites?
Furniture / non living surfaces.
What did the authors of the hypothesis conclude to be the modes of transmission of legionnairres disease?
Tobacco
Water
Air
Therefore:
non-communicable,
lung function,
air-borne,
in water.
How was spread of legionnaires disease made worse by the hotels?
Spread by cooling tower of the hotel’s air conditioning system
Conclusions of acquisition of legionnaires disease?
- May be residentially acquired
- Associated with domestic potable water and disruptions in residential plumbing systems
Potential strategies to reduce legionnaires risk:
- Consistent chlorination of potable water
- Increasing water heater temperatures
- Limiting exposure to aerosols after domestic plumbing repairs.
How is legionella controlled?
1) Chlorine
2) Heat
Is there a vaccine for legionella?
No vaccine (yet?)
What type of microbe is legionella?
Bacteria
What microbe causes legionnaires disease?
Legionella pneumophila
What was the bacterium named after?
named after the legionnaires.
What unusual infections did patients display in 1980 - May 1981?
Patients presented unusual infections
Candida albicans
Kaposi sarcoma
CMV
Pneumocystis carinii
What unusual symptoms did patients display in 1980 - May 1981?
Patients (young) presented unusual symptoms
fever
liver dysfunction
leukopenia
Hodgkins disease
cough, dyspnea
What did all the patients in 1980 - May 1981 have in common?
All were homosexuals
What is the pathway of origin of HIV?
- Came from red-capped mangabeys and greater spot-nosed monkeys (SIVrcm or SIVgsn or other).
- Then adaptation to chimpanzees (SIVcpz (+Vif))(perhaps another animal had it before chimpanzees but this is unknown/unconfirmed. Perhaps this species went extinct)
- Then adaptation to humans (HIV-1)
What are the three major types of HIV?
N, M, and O.
Each derived from a separate transfer event.
What is the probable transmission of HIV between monkeys?
Bush meats
Examples of bush meats?
Bats
Pangolins
Rats
How might have we gotten HIV from the animals?
Probable transmission -> adaptation/mutations
- interactions with animals
- transportation
- urbanization
What is the technique used in phylogenic trees when determining the origin of a disease?
Sequence comparisons
Where have collections of plasma of HIV been found?
Collection of 1,213 plasma
from Léopoldville, DRC, 1959
-> identification of HIV-1
(“ZR59”)
Collection of 27 tissues
from Kinshasa, Kenya, 1960
-> identification of HIV-1
(“DRC60”)
When was the probable entry into humans of HIV?
1884-1924
How does legionnaires and HIV spread so fast in developing countries?
- Settlements
-increased population
-promiscuity
-Sex workers
What are the two partner sutdies
PARTNER-1 : heterosexuals + gay men
PARTNER-2 : gay men
What type of study are the partner studies?
Observational studies
WHat happened in partner-1 study?
MSM couples reported approx 22,000 condomless sex acts and heterosexuals approx 36,000. There were no phylogenetically
linked transmissions occurred over eligible couple years of follow-up, giving a rate of within-couple HIV transmission of zero. All HIV positive partners were using Suppressive Antiretroviral Therapy.
What did partner-2 study show?
Couples reported condomless anal sex a total of 76 088 times. Infections occurred during eligible couple years of follow-up, but none were phylogenetically linked within-couple transmissions, resulting in an HIV transmission
rate of zero. All HIV positive partners were using Suppressive Antiretroviral Therapy.
What do the partner studies show?
Shows how effective the treatments such as ART are and their important role in prevention of HIV.
What is ART?
antiretroviral therapy.
How can we reduce HIV transmission?
- Access to condoms
- Access to ART (treatment)
- Public policies (prevention)
- Education (prevention)
- More research -> cure ? vaccine?
Whats the equation for relative risk (RR)?
RR = (A/(A+B)) / (C/(C+D))
Whats the equation for OR?
OR = (A/C) / (B/D)
Alternatively:
OR = (AD) / (BC)
