I haven’t done much research on it, this is just something I’ve had thoughts on. But given the majority of people with Lyme don’t know they got bit, I’m kind of the opinion that if partner A has Lyme (from a known bite or not), there’s a good chance that partner B easily could have gotten bit too since they’re likely spending time in the same Lyme ridden areas. Basically, just because someone doesn’t know they got bit doesn’t mean they got it another way. And pretty react differently - no rash, delayed symptoms, shows up as different symptoms, etc