Epidemiological Considerations

Question 1

What is the definition of epidemiology?

Answer 1

The study of the distribution and determinants of health-related states or events in specified populations and the application of this study to control of health problems
Tracking a disease within a population

Question 2

What is the definition of infection?

Answer 2

Presence of an infectious organism in an individual or population?

Question 3

What is the definition of disease?

Answer 3

Detectable clinical consequence of infection

Question 4

What is the definition of incubation time?

Answer 4

Time interval between exposure to infection and appearance of disease

Question 5

What is the definition of infectious?

Answer 5

Infected person capable of transmitting infection to others (not everyone who carries a pathogen is infectious)

Question 6

What is more difficult to control: a disease with a long or short incubation time?

Answer 6

Diseases with long incubation times are harder to control because someone who doesn’t know that they are infected may still be able to spread the disease before the onset of symptoms

Question 7

What is the definition of transmission?

Answer 7

The spread of infection

Question 8

What is the definition of symptoms?

Answer 8

What the patient feels (pain, malaise)

This is subjective and can change (cannot be measured)

Question 9

What is the definition of signs (e.g., signs and symptoms)?

Answer 9

Objective and concrete (can be measured through direct observation)

Question 10

What is the definition of communicable?

Answer 10

It the spread of a microbial disease from one individual to another, either direct or indirect
Examples of communicable diseases are gonorrhoea, chickenpox, measles, mumps

Question 11

What is the definition of contagious?

Answer 11

Microbial diseases that easily spread
It is a subcategory of communicable diseases
Example: chickenpox, measles

Question 12

What is the definition of non-communicable?

Answer 12

Microbial diseases that cannot spread through individuals

Example: tetanus

Question 13

Describe the time periods of infection

Answer 13

A susceptible host gets infected. There is a latent period when they are not infectious (generally for short time) because the pathogen is multiplying. Once the organism has multiplied to a high enough concentration, then there is the infectious period. Then the pathogen will leave the host and the host is no longer susceptible

Question 14

Descriebt he time periods of infectious diseases

Answer 14

The susceptible host gets infected and there is an incubation period (no signs or symptoms). When symptoms appear, this is the disease period. The latent period of infection is generally shorter than the incubation period of disease

Question 15

What is an endemic disease?

Answer 15

A disease that exists in a population (this is important for traveling). These diseases exist all the time in at low numbers

Question 16

What is a sporadic disease?

Answer 16

The disease generally does not exist in a certain location but there may be a spike occasionally

Question 17

What is an epidemic?

Answer 17

An outbreak in a larger geographical area

Question 18

What is a pandemic?

Answer 18

An epidemic that spreads across continents

Question 19

What is an acute microbial disease?

Answer 19

A rapidly developing disease with a short duration (e.g., influenza)

Question 20

What is a chronic microbial disease?

Answer 20

A disease that usually develops from chronic infections

They are slow to develop with continual duration (e.g., tuberculosis)

Question 21

What is a latent microbial disease?

Answer 21

A ‘silent’ disease

It is inactivated for certain periods of time (e.g., chickenpox/shingles)

Question 22

What is a cross-sectional study?

Answer 22

Cross-sectional studies measure the frequency of an out- come and/or exposure(s) in a defined population at a par- ticular point in time

Question 23

What type of questions do cross sectional studies answer?

Answer 23

What proportion of the population has evidence of a past infection with Lyme disease?
Is hepatitis B associated with hepatocellular carcinoma?

Question 24

What is a case-control study?

Answer 24

Case–control studies identify people with the outcome (cases) and a representative group of people without the out- come (controls). Cases and controls are then compared with regards to differences in their past exposure

Question 25

What types of questions do case-control studies answer?

Answer 25

Does exposure A cause disease B?
Are women with cervical cancer more likely to be infected with human papillomavirus than women without cervical cancer?
•Is injecting drug use associated with hepatitis C?

Question 26

What is a cohort study?

Answer 26

Cohort studies follow a group of people who do not ini- tially have the outcome of interest and determine whether they develop the disease (descriptive cohort study)

Question 27

What types of questions do cohort studies answer?

Answer 27

How high is the mortality among patients with methicillin-resistant Staphylococcus aureus septicaemia?
Does infection with human herpesvirus-8 cause Kaposi sarcoma in HIV-infected individuals?

Question 28

What is an intervention study?

Answer 28

In an intervention study, disease-free and exposure-free individuals are actively allocated an exposure (interven- tion) or no exposure (no intervention). The two groups are then followed over a period of time and the frequency of the outcome is compared between the two groups

Question 29

What is a randomized intervention study?

Answer 29

Randomized–controlled studies are a subtype of intervention studies and are considered the ‘gold stan- dard’ type of study because, when rigorously designed and conducted, they provide very strong evidence of causal associations. The intervention is allocated at random which means that every participant has the same chance of receiv- ing the intervention

Question 30

What types of questions do intervention studies answer?

Answer 30

Is a new vaccine effective in preventing pneumococcal disease in children?
Do steroids improve the outcome in children with meningococcal disease?

Question 31

How can we characterize outbreaks?

Answer 31

They can be local or widespread