Each dot represents the absolute twitter flu counts for a city. The size of the dot is in the range of 1 to 10 and is proportional to the twitter flu count. All cities with twitter flu counts less than or equal to 10 have the size 1 and all the cities with twitter flu counts greater than or equal to 100 have size 10.
Each dot represents the severity of flu status for a city. The size of the dot is in the range of 1 to 10 and is normalized based on the city population. The baseline of each dot is caluclated as the city population divided by 50,000.