Strep & Fever: leaving inlaws because 7 year old nephew has both strep & fever, don't want to expose our 12 week old. Overreacting or right move?

}i{ • Married ~ FTM
We went to visit our inlaws and my SIL was also on her way with our nephew who just came from urgent care for fever and strep throat. Our LO is 12 weeks and I told my SO that I thought it best to leave to not expose our LO if not necessary. We had been at my Inlwas for at least 2 hours when my SIL arrived, my SO did not want to leave (his friends had arrived to say hello and my FIL was BBQ'ing) and said I was overreacting and being overprotective. I tried to reason that I was only looking at the best interest of our LO and it's not like we don't see them often... Thoughts? FTM here and just didn't see the logic in staying.

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