"Covid 19 in maternity"

My grandson was born in wishaw 4 weeks early . We thought everything was in place for everyone s safety . Covid tests.  ppe social distance etc . Grateful that my son could be with his wife, staff were great. But after the birth they are in a postnatal ward where someone’s test has come back positive. My son is now not allowed to visit and is told to isolate for 10 days. 

1 why were patients put together before test results were back. 

2 why does my son need to isolate when he was in PPE and distanced. 

This makes no sense to me as all the nurses would still be working and not isolating.