Average based on drill down or up when using a measure

I want to get the people that are ill visualized in a line graph diagram. Currently I can visualize the correct numbers for each day. Although when I drill up to the week level or even month level I get the sum of the people that are sick for every day. Which is correct but the issue is that people are often sick for more then 1 day which results in number that are inaccurate on week level or month level (or year). So the possible solution could be to take the average but I don’t know how to do this.

This is the measure I use to get the amount of people that are sick for each day. 

sickness for each day=

var table1 = filter(ADDCOLUMNS(

            Fact,

            "Sick",

            if(RELATED(Dim_Sick) = "Sick", "1", "0")

            ), [Sick] = "1")

var countr = COUNTROWS(table1)

RETURN

CALCULATE(

        countr,

        Fact

        )

Needs to show the average amount of people per week and per month