Things like this are possible.....In the Twilight Zone

Here are two possible scenarios that explain why:
First scenario:
1) Bob is in close contact with Alice without masks
2) Bob is alerted Alice was infected at the time
3) Since Bob has no symptoms he doesn’t quarantine.
4) He is in close contact with Joe.
5) He gets symptoms and learned he got COVID and gave it to Joe.
Second scenario:
1) Bob is in close contact with Alice without masks
2) Bob is alerted Alice was infected at the time
3) Bob gets tested and it comes back positive
4) He quarantines and doesn’t give it to Joe.