Epidemiology

Question 1

Define epidemiology

Answer 1

The study of the distribution and determinants of disease frequency in specified populations

Question 2

What does RO refer to?

Answer 2

Reproduction number. It tells you how contagious an infectious disease is, for example, Ebola is only transmitted by direct contact of bodily fluids and the broken skin or mucous membrane of another individual.

Question 3

Define incidence of disease

Answer 3

The number of new cases of a disease

Question 4

Define prevalence of a disease

Answer 4

The total number of cases, both new and existing

Question 5

Define epidemic

Answer 5

An unusually high number of cases in a population at the same time

Question 6

Define outbreak

Answer 6

An unusual cluster of cases appearing within a short time in a localised population

Question 7

Define pandemic

Answer 7

A widespread or global epidemic

Question 8

Define endemic

Answer 8

A disease that is constantly present in the population

Question 9

Define sporadic

Answer 9

Individual cases occurring in geographically distinct areas

Question 10

Why is it important to study epidemiology?

Answer 10

It allows us to study the causes and spread of disease.

Question 11

Why are disease is spreading?

Answer 11

The modern social, economic, demographic and environmental conditions favour the spread of disease

Question 12

What is meant by the term chain of infection?

Answer 12

It is how a infection spreads. It begins in the reservoir and then via the route of transmission spreads to the host.

Question 13

What is meant by the term pathogen reservoir?

Answer 13

A pathogen reservoir is essential to keep a disease in existence. Carriers of a disease may also act as a disease reservoir.

Question 14

What are the two ways a pathogen reservoir can be characterised?

Answer 14

Animate- which need a living host. They are used by viruses, sexually transmitted infections and respiratory pathogens.

Inanimate- they do not need a living host. Examples of these are Typhus which resides in the soil and cholera which resides in water

Question 15

What are the two methods of contact transmission?

Answer 15

Direct transmission- which may be animal to person or person to person, examples of this include rabies, sexually transmitted infections, measles and Ebola.

Indirect transmission – which is via a nonliving objects (such as sharing bedding or towels) or via air droplets- which is the chosen route of hepatitis B and respiratory viruses.

Question 16

What are the three methods of indirect transmission?

Answer 16

This is transmission via a medium, such as:

• food or water (when food is poorly cooked or stored it may result in the transmission of bacteria, these infections may include salmonella, E. coli or listeria)
• airborne (where are the droplet nuclei travel more than 1 m, and example of this may be TB, measles or streptococci)
• through a vector (arthropods that carry pathogens from one host to another, this may include mechanical transmission- which is the passive transport of the pathogen on the insects feet, for example- or biological transmission- which is infection via an active process, such as an insect bite, examples of these are malaria, yellow fever or the plague)

Question 17

What may happened to the host after exposure to a pathogen?

Answer 17

There could either be no infection or an infection due to the infectivity of the pathogen, the pathogenicity of the pathogen, or the virulence of the pathogen.

Question 18

How can we control disease?

Answer 18

We can reduce the pathogen reservoir, this may include immunisation, quarantine or treatment of the human host, culling or immunisation of the domestic animal host, or attempt to reduce the vectors if it is a wildlife host.
We may also need to reduce pathogen transmission, we could do this by water purification, food treatment or wearing personal protection
We could also reduce the hosts susceptibility to a pathogen this may be done through vaccination and herd immunity.

Question 19

What is active immunity?

Answer 19

Where antibodies are developed in response to an infection

Question 20

What is passive immunity?

Answer 20

Where antibodies are gained from the mother