1 Never use a microwave or conventional oven to pre-heat your flask. 2  If your flask has not been used for some time, rinse with warm water to remove any residual odours.  DO NOT overfill your flask. Leave sufficient space in the neck to fit the stopper.
Prevalence is a measure of disease that allows us to determine a person's likelihood of having a disease. Therefore, the number of prevalent cases is the total number of cases of disease existing in a population.
Incidence is the frequency with which an event occurs within a given time period (such as one year). For example, it could be said that the incidence of new breast cancer cases in 2007 demonstrated 50,000 new cases. By contrast, prevalence refers to how many people currently have that condition this year.