Epidemiology

Question 1

What are the three critical questions when investigating occurrence of disease?

Answer 1

Who was attacked by the disease(sex, age. race)?
When did the disease occur (winter summer, year)?
Where did the cases arise (isolated region or across country)?

Question 2

What is attack rate?

Answer 2

% of people at risk in population

Question 3

What is the attack rate used for?

Answer 3

to predict number of cases expected during an epidemic and to analyze. disease outbreak
Time is not specified because exposure is common and illness is acute

Question 4

What is the difference between primary and secondary cases?

Answer 4

Primary cases acquire disease from the pathogen and secondary cases acquire the disease from primary cases. Depends on source of exposure.

Question 5

How do you calculate the attack rate?

Answer 5

no. of people at risk in whom a certain illness develops/ total number of people at risk
E.g no. of people who ate a certain food and became ill/ total no. of people who ate that food

Question 6

3 important questions to answer when investigating an outbreak

Answer 6

When did the exposure take place?
When were symptoms apparent?
What is the incubation period?

Question 7

Why disease does not develop immediately at time of infection?

Answer 7

Needs time to replicate and depends on site of body in which it replicates
Dose of infectious agent received at time of infection can influence incubation period
Large dose= short incubation

Question 8

Define incubation period

Answer 8

Interval from receipt of infection to onset of clinical illness.
Time it takes for a disease to develop after exposure to a pathogen
depends on disease
disease can be transmitted during incubation

Question 9

What is herd immunity?

Answer 9

principle that if a large % of population is immune to a particular disease, the entire population is protected as well as those who are immune

Question 10

Conditions to meet herd immunity

Answer 10

disease agent must be restricted to a single host species within which transmission occurs
if we have a reservoir in which the organism can exist outside the human host, herd immunity will not operate because we have another means of transmission
infections must induce solid immunity. If immunity is only partial we will not build up a large proportion of immune people in the community

Question 11

Types of exposure

Answer 11

single exposure- exposed once
Common-vehicle exposure- group of people have eaten contaminated food and become ill
Multiple exposure- exposed more than once

Question 12

Define endemic, epidemic and pandemic

Answer 12

Endemic- habitual occurrence of a disease within a given geographical area
Epidemic- occurrence in a a community or region of a group of illnesses of similar nature
Pandemic-worldwide epidemic

Question 13

Types of non-clinical diseases

Answer 13

Preclinical -not yet clinically apparent but is destined to become a clinical disease
Subclinical-not yet clinically apparent and is not destined to become clinically apparent. This type of disease is often diagnosed by serologic (antibody) response or culture.
Persistent (chronic)- person fails to hake off infection and it persists for years at times for life
Latent- infection with no active multiplication of the agent

Question 14

Iceberg concept of infectious diseases

Answer 14

Only a small portion of infections result in clinical disease

Question 15

Modes of disease transmission

Answer 15

Direct- droplet (cough, sneeze), direct physical contact( sexual), transplacental ( mother to child)
Indirect- food, air water borne, indirect physical contact( touching surfaces), vector e.g insect

Question 16

Portals of entry

Answer 16

genital
respiratory (upper and lower airways)
urinary
gastrointestinal (mouth)
damaged skin(cuts and burns)

Question 17

Factors that may be associated with increased risk of disease

Answer 17

Host charcteristics- age,sex,race,religion.customs,occupation
Type of agents- virus, bacteria, alcohol, smoke, radiation
Environmental factors- temperature, humidity, altitude

Question 18

Epidemiologic triad of disease

Answer 18

Host
/ i \
Vector \
/ / \
Agent ——- Environment

Question 19

Two approaches of disease prevention

Answer 19

Population-based
High risk approach
Can be combined

Question 20

Population based approach

Answer 20

applied to entire population
may use mass media or other health education approaches
must be inexpensive and noninvasive
can be considered public health approach

Question 21

High risk approach

Answer 21

screening for certain disease
may be restricted to children from high risk families
may be more expensive, invasive or inconvenient
must be able to identify individuals with disease
require clinical action to identify high risk groups

Question 22

History of epidemiology

Answer 22

John snow -cholera
Edward Jenner- small pox
Ignaz Semelweis-childbed fever

Question 23

The epidemiological approach

Answer 23

1- identify cause and distribution of disease
determine if there is an association between exposure factor or characteristic and development of disease
if pattern and association exists determine if there is a causal relationship
-if there is a causal relationship: does factor increase risk of disease development
lead to development of disease
cause disease

Question 24

Population data for clinical practice comes from:

Answer 24

surgeries
autopsies
experience with large group of patients who have had the disease
clinical trials

Question 25

3 types of prevention

Answer 25

Primary: do not have disease, prevent disease from developing, immunize, prevent exposure to environmental factor
Secondary: have disease but no clinical signs or symptoms objective is to catch disease early for effective treatment
Tertiary: have disease, signs and symptoms, prevent complications with prompt and appropriate treatment combined with ancillary approaches such as physical therapy

Question 26

Why identify subgroups

Answer 26

we can direct preventative efforts e.g screening for early disease detection for those who don’t know they have the disease
identify factors or characteristics that put them at risk so we can modify

Question 27

What do epidemiologist investigate/ objectives

Answer 27

Identify etiology of disease
Determine extent
Study progression
Evaluate preventative and therapeutic measures
Develop public health policy