Evolution of weekly<unk> rates of Dengue fever in Cambodia from January 2002 to December 2008. In epidemiology,<unk> is a measure of the probability of occurrence of a given medical condition in a population within a specified period of time. Although sometimes loosely expressed simply as the number of new cases during some time period, it is better expressed as a proportion or a rate with a denominator.
Incidence 
Prevalence
Risk factor
Mortality rate
Case fatality rate
Dose 
Transmission risks and rates
Infection rate