Well ****.
My nephew babysat my kids Monday/Tuesday. Today he had no sense of taste or smell, so he got tested and it came back positive. He wore a mask the whole time he was with my kids, so hopefully that helped. We have a newborn, by the way. On the other hand, my wife got her 1st dose of Covid vaccine yesterday (she's a nurse) and she's breastfeeding. If the theory holds, that should help help the newborn hopefully.
If my family gets Covid while we're in the (seemingly) home stretch of this pandemic, I'm gonna be extra upset. We haven't done anything or gone anywhere since March. Kids do school from home. I work from home. My wife has been off for 12 weeks for maternity leave and just now went back to work. Before then, she also mostly worked from home. My nephew is extremely careful, too. He doesn't go anywhere other than to babysit for us on occasion. He has no idea where he might have got it.
EDIT: To be clear, I don't blame my nephew at all. He's an extremely responsible person that I obviously trust enough to care for my 4 kids ages 9 and under. I blame this stupid ****ing country that could have gotten this **** under control months ago but made the choice not to.