RSV- Stay home?

My son's great great grandmother was with him almost all day Monday. On Thursday she was diagnosed with RSV and hospitalized. His great grandma and grandma swear that no one else in the house is sick and not too worry (they watch him Mondays and Fridays while I'm at work). But- I saw that the gestational period for RSV can be 4-6 days after initial exposure!

He's already getting congested and coughing and sneezing (we will be taking him to get a test done when the clinic opens).

If he is RSV negative and feeling better on Monday should I still find someone else to watch him on Monday? Or can he go to his Grandma's as long as no one is showing any symptoms?