Are you writing about my Mum and late Dad?
They lived across the country from me and my DB and DS. Consequently we each only went a few times/year.
Quite often , in our weekly phonecall, my Mum would tell me that they’d had upset stomachs all week.
As we were vegetarian we’d usually take the makings of our meals but in the fridge were old saved dishes, fresh meat potentially dripping into old saved food.
When they couldn’t drive they discovered online shopping. More or less the same order every week - whether they eaten last weeks or not.
Our visits became weekly. One of the jobs we did was quietly sort the fridge. Chucking out the mould, suspect, rotting in the bags, sour food.
Turned out my DB and DS did the same on their visits too.
The house was stuck in a late 60s/70s timewarp. Carpet tiles were a thing back then - but not everyone has them in the kitchen. (And with a dog)
In terms of mild food poisoning things have improved. They moved back nearer us. My Mum can’t cook for herself now nor order online. The fridge is clean, no weekold leftovers, lino in the kitchen.