Difference  between Incidence, Prevalence and Occurrence?


  • Incidence of a disease:  is the number of new cases of the disease in a specific time frame. These figures are used to predict if the amount of cases are increasing or decreasing. A disease is classified according to their incidence in our society.
  • Prevalence of a disease: is the number of infected people at the one time, covering both old and new cases at that time. The function of this is to show periodic fluctuation or trends over time.
  • Occurrence of a disease: is how many times the diseases occurs.



Examples of factors that might cause persons to migrate.


Factors that would influence a person to migrate may vary, depending on where they live. In some 3rd world countries it can be “for a shot at a better life” or in countries where violence is occurring, it can be to escape this. In some cases it can be due to work or a lust to travel. As Migrants, people are vectors and can carry disease from one confined state to another. This can cause problems for the people who have not had contact with it before as they have no immunity to it.


What is meant by the term population at risk?

The term “Population at risk” from Moby’s Dictionary is referring to a group of people who share a common characteristic that causes them to be potentially subject to a specific risk,.  In this case the risk may be illness, for example, the elderly or those who suffer from immune deficiencies, like HIV, are more at risk to pneumonia because their immune system is weakened more so than the average person who would be able to fight it off in it’s earlier stages.  



The major steps necessary to investigate the possible outbreak of an epidemic.


Epidemics occur when there are sudden increases in frequency above endemic levels, Hyperendemic. An outbreak is defined when the amount of cases of the disease is bigger than the number expected at given point of time or location.

In order to identify an outbreak of a disease, you need to know the statistics. Secular or Periodic Trends which map out the changes over a period of time are used in conjunction with surveillance, Epidemiological studies and mathematical modelling in order to predict the future outbreaks.

  • Who the disease affects,
  • Time of the year (Seasonal trends must be monitored to predict the chance of an epidemic occurring).
  • Sign and symptoms are.
  • Method of transmission
  • Recovery time and length of incubation period,