Remove the cabin filters from the engine compartment, I know on the V8's they are on both sides just at the left and right bottom corners of the windshield.
Then, use a can-spray disinfectant, like Lysol, and spray into the vent intake holes, where the cabin filters sit.
This is done with the fan at full speed (A/C can be off) and repeat spraying a few times in like a minute intervals. Leave doors open.
You may also want to drape some old bedsheets over your seats and areas of the interior, as the disinfectant could blow out of the A/C vents and get on everywhere.
This step should solve the problem, and you should have fresh clean scent thru' the vents, for at least a few months up to maybe 6 months.
It will return with time, and you will have to repeat the process.