1 For best results from your flask, before use, pre-fill for about 3 minutes, using either hot water for hot drinks or cold water for chilled drinks. 2  Never use a microwave or conventional oven to pre-heat your flask.  If your flask has not been used for some time, rinse with warm water to remove any residual odours.
2. : the degree to which something is prevalent; especially: the percentage of a population that is affected with a particular disease at a given time.
as the number of cases out of a certain population. For example, the prevalence of HIV/AIDS in. Australia in 2011 was 0.155%, or 115 out of every 100 000 people. 2 This is also known as âpointâ. prevalence as it provides a picture of what is occurring at a certain point of time.