My 2nd cousin caught it while traveling his wife. VERY early in the game with regard to confirmed cases.....pre-shutdown / everyone still flying.
He and his wife were around the same people doing the same things and flew back home together sitting side by side. He got very, very ill 7-10 days after their return.
She had not only traveled with him there and back, but was sleeping in the same bed with him before/during his early symptomatic phase and nursing him while he got sicker.....thinking it was a severe sinus infection because he was run down after the trip (late nights, drinking, etc). He crashed and tested positive when he was admitted to the hospital and then ICU.
She tested negative multiple times as did their children who had the same exposure around the house, save the bed.
My understanding is that she and the kids didn't even test positive for the antibodies that would have indicated her as positive / asymptomatic.
It's anecdotal but there are so many of these occurrences that there has to be something there with regard to natural immunity or the spread would be worse than it already is.