Point prevalence
In epidemiology, point prevalence is a measure of the proportion of people in a population who have a disease or condition at a particular time, such as a particular date. It is like a snap shot of the disease in time. It can be used for statistics on the occurrence of chronic diseases. This is in contrast to period prevalence which is a measure of the proportion of people in a population who have a disease or condition over a specific period of time, say a season, or a year.
Point prevalence can be described by the formula:
Prevalence = Number of existing cases on a specific date ÷ Number of people in the population on this date
References
Gerstman, B.B. (2003). Epidemiology Kept Simple: An Introduction to Traditional and Modern Epidemiology (2nd ed.). Hoboken, NJ: Wiley-Liss.