General Discussion
In reply to the discussion: Question about Covid [View all]wnylib
(21,446 posts)according to which covid variant is involved.
The original strain's incubation period was 14 days. Symptoms usually did not show up before 7 days after exposure. That changed considerably with the later, more infectious variants, as evidenced by the delta mutation which could double in a community within 2 weeks.
Other variants after delta could double in an area in less than two weeks, sometimes in just one week or less.
So, the couple in question. The husband might have been infectious before he had symptoms. The wife was exposed during that time, but didn't have either symptoms or enough antibodies to show up in a test until later. She could have been infectious when your friend was with her.
The timing also varies with individuals, due to differences in general health, individual immune systems, if vaccinated and how long ago, if boosted and how long ago.
In other words, there is no single, definitive sequence of time and exposure. Too many variables in both the virus and the people.