L14 - preventing infection

Question 1

Define the following phrases:

• endemic disease
• outbreak
• epidemic
• Pandemic

Answer 1

Endemic - The usual background rate of disease, a disease may be more prevalent in the Winter, if this is normal though it is endemic
Outbreak - Two or more cases linked in time and place
Epidemic - A rate of infection greater than the usual background rate
Pandemic - A very high rate of infection spreading across many regions/ countries/continents

Question 2

What is meant by R0 (Basic reproduction number)

Answer 2

The average number of cases one case generates over the course of its infectious period, in an otherwise uninfected, non-immune population

Question 3

Give an example of a disease with a particularly high R0

Answer 3

Measles/ pertussis (whooping cough)

Question 4

There are many reasons we see outbreaks, epidemics and pandemics. Give a brief explanation of how the following could cause them:

1) New hosts
2) Changes in practice
3) New pathogens
4) Antigenic shift

Answer 4

1) - Babies because they only have a small amount of immunity form their Mothers which disappears quickly
2) - Homosexuality meaning more anal intercourse increased the likelihood of HIV in the population
3) Mutated viruses/ resistant bacteria
4) This means two or more strains of viruses combine to have a new selection of antigens on their surface to which no one is yet immune

Question 5

Give some factors that affect transmittability of a microbe

Answer 5

• Type of micro-organism
• How the micro-organism is presented - e.g. IV/on the skin. Some can only infect via the skin other by the blood
• Immunity of the potential host

Question 6

LO question

-Describe some interventions that can be made to prevent infection

Answer 6

• Reduction/ eradication of said pathogen - e.g. decontamination/sterilisation/antibacterials
• Improved general health often leads to immunity - nutrition/vaccination
• Changes in behaviour
• Protective equipment. e.g. long socks in mosquito country
• Changes in environment/engineering e.g. clean showers to prevent legionarres disease

Question 7

what is meant by ‘herd immunity’

Answer 7

The idea is that if part of the community is vaccinated it prevents spread to the total or very large proportion of the community because the vaccinated people cant act as vectors. This prevents epidemics and pandemics

Question 8

Controlling infection is good because we get decreased incidence of it however on the flip side it can lead to exposure of diseases in later life and thus more severe consequences, explain how

Answer 8

Decreased exposure to the pathogen means decreased immunity to it, thus increased susceptibility. It means that when an individual encounters it it is usually later in life and in diseases like polio this can mean a disease that is asymptomatic if contracted in childhood can cuase life threatening consequences in adulthood e.g. polio/ chicken poc

Question 9

What phenomenon is the cause of pandemics?

Answer 9

Antigenic shift