Before the internet (and still sometimes today) ham radio operators exchange postcards to confirm contacts with one another. Some of them collect contacts.
I exchanged QSL cards with an operator in Antarctica once. It was a very short contact via morse code :-)
Close proximity.
The incubation period is said to be 3-14 days (IIRC) and during that period a person is asymptomatic but is going around shedding virus that will contaminated surfaces and later infect others. It is said to be very infectious.
Whether to believe that or not, it's up to you. That's what they said tho.
Lots of rumors. No firm sauce.