Attack rate - number of cases in the population relative to the total number of people at risk of being infected in the population (a measure of ‘risk’).

Case definition – used to define whether the individual is considered to have the disease of interest; includes possible/ suspected case definition (e.g. based on common symptoms), clinically confirmed case definition (e.g. based on stricter list of clinical symptoms), and laboratory confirmed case definition (confirmed via laboratory tests).

Case fatality ratio – the proportion of cases with the disease that die.

Causative agent – the organism that is found to cause the disease.

Effective contact – contact with the infectious agent or individual that leads to the infection being successfully transmitted.

Endemic – disease that occurs regularly or is native to an area.

Epidemic – occurrence of cases of disease that are in excess of what is normally expected.

Epidemic curve – graph to describe the occurrence of cases over time.

Incubation period – the time period between the point of infection and the onset of symptoms.

Infectious period – the time period during which the infectious agent may be transmitted.

Latent period (pre-infectious period) – the time period from the point of infection to the beginning of the infectious period.

Outbreak - excess cases of disease above normal levels occur in a defined geographical area, for example a particular community or village.