Am I overreacting?

I just had my son 9 days ago. On Saturday my sister in law came over to see the baby with her husband and my nephews and my 1 year old niece. we allowed the nephews to held the baby for a minute and then sent them off to do something else. 1 hour in I realized my niece had a runny nose and an icky cough. I came out from pumping and I was horrified. SIL said it was just allergies or teething. Now my baby is horribly congested and raspy. We took him to the ER and they said he has some kind of upper respiratory virus but not covid or rsv. I’m am livid. My baby was born at 37 weeks so he’s barely not premature and my pregnancy was very hard so I can’t handle anything happening to him. I basically never want to talk to SIL or BIL again. We were best friends before so it’s hard. I don’t know if it’s just my hormones or I’m right to hate them for this?!