COUNTIF formula only after meeting another cell's not null criteria

Having trouble building a nested formula for a COUNTIF function. I have attached a partial example of what I'm trying to achieve. I have a cubed section of patient cases with some simple formula. Each cubed section after this is per Unit (in the example I've only included one Unit example instead of the many that I have). Under the "# New Cases by Unit" I would like the COUNTIF criteria to first look at the "Case ID" column G, only if the cell is NOT NULL, I would like for the COUNTIF function to look at the range of dates in column H "Date of onset of symptoms", if any of the dates match the date in K3, I want it to count how many cases on that selected date from column H.

Hopefully the attached example is a little clearer than my explanation. Any help would be greatly appreciated!!