Grocery store worker here.. When a customer has their own bags, they usually want us to fill them to capacity and that means putting their raw meat in with their other food. When we use plastic, we bag their meat separate unless the customer requests otherwise (they usually don't). Also, some people never wash or clean their bags. I've put food into bags that reeked of cat piss, were littered with animal fur (cats love to sleep/hide in them), or were infested with insects so it doesn't surprise me that people are getting sick.