Epidemiology Flashcards
Define epidemiology
The study of the distribution and determinants of disease frequency in specified populations
What does RO refer to?
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.
Define incidence of disease
The number of new cases of a disease
Define prevalence of a disease
The total number of cases, both new and existing
Define epidemic
An unusually high number of cases in a population at the same time
Define outbreak
An unusual cluster of cases appearing within a short time in a localised population
Define pandemic
A widespread or global epidemic
Define endemic
A disease that is constantly present in the population
Define sporadic
Individual cases occurring in geographically distinct areas
Why is it important to study epidemiology?
It allows us to study the causes and spread of disease.
Why are disease is spreading?
The modern social, economic, demographic and environmental conditions favour the spread of disease
What is meant by the term chain of infection?
It is how a infection spreads. It begins in the reservoir and then via the route of transmission spreads to the host.
What is meant by the term pathogen reservoir?
A pathogen reservoir is essential to keep a disease in existence. Carriers of a disease may also act as a disease reservoir.
What are the two ways a pathogen reservoir can be characterised?
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
What are the two methods of contact transmission?
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.
What are the three methods of indirect transmission?
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)
What may happened to the host after exposure to a pathogen?
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.
How can we control disease?
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.
What is active immunity?
Where antibodies are developed in response to an infection
What is passive immunity?
Where antibodies are gained from the mother
