New HVAC unit installed backwards causing illness?

Hello. My mom's boyfriend installed a new HVAC unit about 4 months ago. It was installed backwards, taking in air through the vents, and blowing out air through the register. My question is this...they alternate between staying at his villa and hers. They have stayed at his place twice in the past couple months, and they developed what the ER called "bacterial pneumonia." It was not Covid. They stayed there again last week, and he is exhibiting symptoms again. My question is this...we live in Florida, where it is very humid and hot. Can the period of time that the system was backwards have drawn in fungus, bacteria, etc. THROUGH the vents and into the air handler, etc., that could now be blowing back out through the vents and making them sick? I am starting to think it is a Legionnaire type illness caused by these people who installed it backwards. They are 83, and it was very difficult for them to overcome the first episode, and now we are facing a second. Also, it is now not blowing cold air at all, and they are now saying it is a leak in the coil and they will have to order a new coil. I am afraid for them to stay there and breathe the air.
Thoughts, please. Should we call the health department or another company and get the air tested?
Thank you.

source https://hvac-talk.com/vbb/threads/2241677-New-HVAC-unit-installed-backwards-causing-illness?goto=newpost