Infectious Disease Epidemiology

Question 1

define the following:
* epidemic
* pandemic
* incidence
* prevalence

Answer 1

• Epidemic: This is when a disease suddenly starts spreading and affects many people in a particular area or community.
• Pandemic: When an epidemic spreads across whole countries or the world, affecting lots of people everywhere, it’s called a pandemic.
• Incidence - measure of probability of infection
• Incidence rate is the no of new cases per population at risk in given time period
• Prevalence - proportion of infection found to be affecting a particular population

Question 2

define the following
*index case
*primary case
*secondary case
*tertiary case

Answer 2

Definitions transmission
* Index - first case identified
* Primary - case that brings infection into a population
* Secondary - infected by a primary case
* Tertiary - infected by a secondary case

Question 3

• how are viruses transmitted?

*what are the factors that influence virus transmission

Answer 3

how are viruses transmitted:
*directed contact (pathogen survives best inside the body)
*indirect contact (pathogen survives harsh environment–pick up pathogen from surface/air e.g. flu,norovirus
*droplets (pathogens in droplets; but don’t survive long this way)
*airborne (pathogens aerosolised + stay infective in air longer)
*faecal/oral (through contaminated water/food)
*insect vectors e.g. Zika virus
*blood borne
*mother-to-child
*sexual transmission

what are the factors that influence virus transmission;

Question 4

explain herd immunity

Answer 4

• Indirect protection from infection of susceptible members of population and the protection of populations as a whole - brought about by presence of immune individuals
  % of individuals in a population who need to be immunised in order to achieve herd immunity varies and depends on factors like vaccine effectiveness and disease characteristics

e.g. Measles vaccine is 90-95% so out of every 100 children given vaccine, 5-10% not protected - so to protect those without immunity, need 95% of individuals to be protected

Question 5

what do we mean by R0 number

Answer 5

R0, or the basic reproduction number/rate, refers to the contagiousness and transmissibility of infectious pathogens. R0 varies depending on a variety of factors and is critical in public health management to ensure infectious epidemics (or global pandemics) are controlled.

Question 6

what is the difference between and epidemic + an endemic

Answer 6

• Epidemic is actively spreading - new cases of diseases substantially exceeding what is expected
• Endemic is constant presence in specific location - malaria is endemic to parts of Africa - Ice is endemic to Antarctica

Question 7

which cell does HIV take over first?

Answer 7

• Local macrophages patrol tissue fluids in search of foreign particles - dendritic cells in-between goblet cells, have processes which stretch above mucosal layer to constantly check whasgoingon to present antigen to lymph nodes
  **
  *HIV takes advantage of dendritic cells since it gets to lymph node to do its thang on CD4 cell**

Question 8

what is indicative that a baby has croup infection

Answer 8

n.b. croup infection causes swelling of trachea
* barking seal sound whilst crying
*rapid breathing
* fever
*runny nose

Question 9

how do we diagnose Respiratory tract infections

Answer 9

symptoms + Nasopharyngeal swab + PCR - polymerase chain reaction